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• cannot delete IPv6 default gateway

  - by NulledPointer

  The commands below should be pretty self-explanatory. Please note that the route for which i get failure is obtained by RA and has very less expiry ( e Flag in UDAe). @vm:~$ ip -6 route 2001:4860:4001:800::1002 via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 2001:4860:4001:800::1003 via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 2001:4860:4001:800::1005 via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 2001:4860:4001:803::100e via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 fd00:ffff:ffff:fff1::/64 dev eth1 proto kernel metric 256 expires 2592300sec fe80::/64 dev eth1 proto kernel metric 256 default via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1 default via fe80::20c:29ff:fe87:f9e7 dev eth1 proto kernel metric 1024 expires 1776sec @vm:~$ @vm:~$ @vm:~$ @vm:~$ sudo route -6 delete default gw fe80::20c:29ff:fe87:f9e7 @vm:~$ ip -6 route 2001:4860:4001:800::1002 via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 2001:4860:4001:800::1003 via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 2001:4860:4001:800::1005 via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 2001:4860:4001:803::100e via fe80::20c:29ff:fe87:f9e7 dev eth1 proto static metric 1024 fd00:ffff:ffff:fff1::/64 dev eth1 proto kernel metric 256 expires 2592279sec fe80::/64 dev eth1 proto kernel metric 256 default via fe80::20c:29ff:fe87:f9e7 dev eth1 proto kernel metric 1024 expires 1755sec @vm:~$ @vm:~$ @vm:~$ sudo route -6 delete ::/0 gw fe80::20c:29ff:fe87:f9e7 dev eth1 SIOCDELRT: No such process @vm:~$ @vm:~$ @vm:~$ route -n6 Kernel IPv6 routing table Destination Next Hop Flag Met Ref Use If 2001:4860:4001:800::1002/128 fe80::20c:29ff:fe87:f9e7 UG 1024 0 0 eth1 2001:4860:4001:800::1003/128 fe80::20c:29ff:fe87:f9e7 UG 1024 0 0 eth1 2001:4860:4001:800::1005/128 fe80::20c:29ff:fe87:f9e7 UG 1024 0 0 eth1 2001:4860:4001:803::100e/128 fe80::20c:29ff:fe87:f9e7 UG 1024 0 0 eth1 fd00:ffff:ffff:fff1::/64 :: UAe 256 0 0 eth1 fe80::/64 :: U 256 0 0 eth1 ::/0 fe80::20c:29ff:fe87:f9e7 UGDAe 1024 0 0 eth1 ::/0 :: !n -1 1 349 lo ::1/128 :: Un 0 1 3 lo fd00:ffff:ffff:fff1:a00:27ff:fe7f:7245/128 :: Un 0 1 0 lo fd00:ffff:ffff:fff1:fce8:ce07:b9ea:389f/128 :: Un 0 1 0 lo fe80::a00:27ff:fe7f:7245/128 :: Un 0 1 0 lo ff00::/8 :: U 256 0 0 eth1 ::/0 :: !n -1 1 349 lo @vm:~$ UPDATE: Another question is whats the use of link local address as the default route?

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• Why "scope link" ipv6 address can be pinged via interfaces which they are not active on

  - by olagu

  [root@2_01 ~]# /sbin/ip -6 addr show pubeth0 inet6 2001:1::6/64 scope global inet6 2001:1::1/64 scope global inet6 fe80::20c:29ff:fe69:f9e8/64 scope link [root@v2_01 ~]# /sbin/ip -6 addr show pubeth1 inet6 fe80::20c:29ff:fe69:f906/64 scope link [root@2_01 ~]# ping6 fe80::20c:29ff:fe69:f9e8%pubeth1 PING fe80::20c:29ff:fe69:f9e8%pubeth1(fe80::20c:29ff:fe69:f9e8) 56 data bytes 64 bytes from fe80::20c:29ff:fe69:f9e8: icmp_seq=1 ttl=64 time=0.259 ms --- fe80::20c:29ff:fe69:f9e8%pubeth1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 286ms rtt min/avg/max/mdev = 0.259/0.259/0.259/0.000 ms [root@2_01 ~]# ping6 fe80::20c:29ff:fe69:f9e8%pubeth0 PING fe80::20c:29ff:fe69:f9e8%pubeth0(fe80::20c:29ff:fe69:f9e8) 56 data bytes 64 bytes from fe80::20c:29ff:fe69:f9e8: icmp_seq=1 ttl=64 time=0.057 ms --- fe80::20c:29ff:fe69:f9e8%pubeth0 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 390ms rtt min/avg/max/mdev = 0.057/0.057/0.057/0.000 ms Why can I ping6 "fe80::20c:29ff:fe69:f9e8" via pubeth1?

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• Special character into querystring .NET

  - by user353089

  I need to send the follow querystring: http://prod.intranet.siemens.com.br/drvs/index.aspx?page=2&pag=4&varpatch=%20C:\Documents%20and%20Settings\OPE253\My%20Documents\Ca$@#! Then i try to assing this to a string,but .NET break string at http://prod.intranet.siemens.com.br/drvs/index.aspx?page=2&pag=4&varpatch=%20C:\Documents%20and%20Settings\OPE253\My%20Documents\Ca$@ '#" do not appears in querystring Any ideas?

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• Does an insert made in a transaction is visible by SELECT before transaction is commited

  - by 20c

  I need a confirmation. Client 1 insert rows in a table inside a transaction. Client 2 request this table with a SELECT. If on this client isolation level is set to READ COMMITTED, can you confirm that the SELECT won't returns the rows that aren't yet committed by Client 1. Thanks

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• Diophantine Equation [closed]

  - by ANIL

  In mathematics, a Diophantine equation (named for Diophantus of Alexandria, a third century Greek mathematician) is a polynomial equation where the variables can only take on integer values. Although you may not realize it, you have seen Diophantine equations before: one of the most famous Diophantine equations is: X^n+Y^n=Z^n We are not certain that McDonald's knows about Diophantine equations (actually we doubt that they do), but they use them! McDonald's sells Chicken McNuggets in packages of 6, 9 or 20 McNuggets. Thus, it is possible, for example, to buy exactly 15 McNuggets (with one package of 6 and a second package of 9), but it is not possible to buy exactly 16 nuggets, since no non- negative integer combination of 6's, 9's and 20's adds up to 16. To determine if it is possible to buy exactly n McNuggets, one has to solve a Diophantine equation: find non-negative integer values of a, b, and c, such that 6a + 9b + 20c = n. Problem 1 Show that it is possible to buy exactly 50, 51, 52, 53, 54, and 55 McNuggets, by finding solutions to the Diophantine equation. You can solve this in your head, using paper and pencil, or writing a program. However you chose to solve this problem, list the combinations of 6, 9 and 20 packs of McNuggets you need to buy in order to get each of the exact amounts. Given that it is possible to buy sets of 50, 51, 52, 53, 54 or 55 McNuggets by combinations of 6, 9 and 20 packs, show that it is possible to buy 56, 57,..., 65 McNuggets. In other words, show how, given solutions for 50-55, one can derive solutions for 56-65. Problem 2 Write an iterative program that finds the largest number of McNuggets that cannot be bought in exact quantity. Your program should print the answer in the following format (where the correct number is provided in place of n): "Largest number of McNuggets that cannot be bought in exact quantity: n" Hints: Hypothesize possible instances of numbers of McNuggets that cannot be purchased exactly, starting with 1 For each possible instance, called n, a. Test if there exists non-negative integers a, b, and c, such that 6a+9b+20c = n. (This can be done by looking at all feasible combinations of a, b, and c) b. If not, n cannot be bought in exact quantity, save n When you have found six consecutive values of n that in fact pass the test of having an exact solution, the last answer that was saved (not the last value of n that had a solution) is the correct answer, since you know by the theorem that any amount larger can also be bought in exact quantity

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• PHP create image to display email address?

  - by Teddkl

  Using PHP: How can I create an image to display an email address (to help reduce spam)? Meaning, if I want to display "[email protected]" on my web page, since crawlers can easily find that text - I want to display the email address as an image that says "[email protected]". How do I do that? I want the font to be: color: #20c font: 11px normal tahoma

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• vmware player - ubuntu can resolve hostname but ping fails

  - by recursive_acronym

  Using VMware players on Windows 7 with a Ubuntu 10.04 guest. When I ping it resolves the ip address but the ping fails. Hopefully this is a local issue as I don't have access to any of the network equipment (routers, etc). vmware tools is installed. Is there any other information I can provide to help resolve this? eth0 Link encap:Ethernet HWaddr 00:0c:29:83:4f:c0 inet addr:192.168.163.129 Bcast:192.168.163.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe83:4fc0/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:475 errors:0 dropped:0 overruns:0 frame:0 TX packets:179 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:50006 (50.0 KB) TX bytes:16701 (16.7 KB) Interrupt:19 Base address:0x2024 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:8 errors:0 dropped:0 overruns:0 frame:0 TX packets:8 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:480 (480.0 B) TX bytes:480 (480.0 B)

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• LXC Container Networking

  - by digitaladdictions

  I just started to experiment with LXC containers. I was able to create a container and start it up but I cannot get dhcp to assign the container an IP address. If I assign a static address the container can ping the host IP but not outside the host IP. The host is CentOS 6.5 and the guest is Ubuntu 14.04LTS. I used the template downloaded by lxc-create -t download -n cn-01 command. If I am trying to get an IP address on the same subnet as the host I don't believe I should need the IP tables rule for masquerading but I added it anyways. Same with IP forwarding. I compiled LXC by hand from the following source https://linuxcontainers.org/downloads/lxc-1.0.4.tar.gz Host Operating System Version #> cat /etc/redhat-release CentOS release 6.5 (Final) #> uname -a Linux localhost.localdomain 2.6.32-431.20.3.el6.x86_64 #1 SMP Thu Jun 19 21:14:45 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux Container Config #> cat /usr/local/var/lib/lxc/cn-01/config # Template used to create this container: /usr/local/share/lxc/templates/lxc-download # Parameters passed to the template: # For additional config options, please look at lxc.container.conf(5) # Distribution configuration lxc.include = /usr/local/share/lxc/config/ubuntu.common.conf lxc.arch = x86_64 # Container specific configuration lxc.rootfs = /usr/local/var/lib/lxc/cn-01/rootfs lxc.utsname = cn-01 # Network configuration lxc.network.type = veth lxc.network.flags = up lxc.network.link = br0 LXC default.confu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:12:30:f2 brd ff:ff:ff:ff:f #> cat /usr/local/etc/lxc/default.conf lxc.network.type = veth lxc.network.link = br0 lxc.network.flags = up #> lxc-checkconfig Kernel configuration not found at /proc/config.gz; searching... Kernel configuration found at /boot/config-2.6.32-431.20.3.el6.x86_64 --- Namespaces --- Namespaces: enabled Utsname namespace: enabled Ipc namespace: enabled Pid namespace: enabled User namespace: enabled Network namespace: enabled Multiple /dev/pts instances: enabled --- Control groups --- Cgroup: enabled Cgroup namespace: enabled Cgroup device: enabled Cgroup sched: enabled Cgroup cpu account: enabled Cgroup memory controller: /usr/local/bin/lxc-checkconfig: line 103: [: too many arguments enabled Cgroup cpuset: enabled --- Misc --- Veth pair device: enabled Macvlan: enabled Vlan: enabled File capabilities: /usr/local/bin/lxc-checkconfig: line 118: [: -gt: unary operator expected Note : Before booting a new kernel, you can check its configuration usage : CONFIG=/path/to/config /usr/local/bin/lxc-checkconfig Network Config (HOST) #> cat /etc/sysconfig/network-scripts/ifcfg-br0 DEVICE=br0 TYPE=Bridge BOOTPROTO=dhcp ONBOOT=yes #> cat /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 ONBOOT=yes TYPE=Ethernet IPV6INIT=no USERCTL=no BRIDGE=br0 #> cat /etc/networks default 0.0.0.0 loopback 127.0.0.0 link-local 169.254.0.0 #> ip a s 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:12:30:f2 brd ff:ff:ff:ff:ff:ff inet6 fe80::20c:29ff:fe12:30f2/64 scope link valid_lft forever preferred_lft forever 3: pan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN link/ether 42:7e:43:b3:61:c5 brd ff:ff:ff:ff:ff:ff 4: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN link/ether 00:0c:29:12:30:f2 brd ff:ff:ff:ff:ff:ff inet 10.60.70.121/24 brd 10.60.70.255 scope global br0 inet6 fe80::20c:29ff:fe12:30f2/64 scope link valid_lft forever preferred_lft forever 12: vethT6BGL2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether fe:a1:69:af:50:17 brd ff:ff:ff:ff:ff:ff inet6 fe80::fca1:69ff:feaf:5017/64 scope link valid_lft forever preferred_lft forever #> brctl show bridge name bridge id STP enabled interfaces br0 8000.000c291230f2 no eth0 vethT6BGL2 pan0 8000.000000000000 no #> cat /proc/sys/net/ipv4/ip_forward 1 # Generated by iptables-save v1.4.7 on Fri Jul 11 15:11:36 2014 *nat :PREROUTING ACCEPT [34:6287] :POSTROUTING ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A POSTROUTING -o eth0 -j MASQUERADE COMMIT # Completed on Fri Jul 11 15:11:36 2014 Network Config (Container) #> cat /etc/network/interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp #> ip a s 11: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 02:69:fb:42:ee:d7 brd ff:ff:ff:ff:ff:ff inet6 fe80::69:fbff:fe42:eed7/64 scope link valid_lft forever preferred_lft forever 13: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever

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• CentOS Client - Unable to Establish iSCSI connection with multiple interfaces on the initiator

  - by slashdot

  So after upgrading to CentOS 6.2, I am seemingly no longer able to login into my iSCSI targets. I have multiple interfaces on different subnets on the system, and I first thought that it had to do with the fact that I may not be binding correct interfaces, which seems to be the case when looking at netstat, as this is clearly wrong: [root]? netstat -na|grep .90 tcp 0 1 10.10.100.60:42354 10.10.8.90:3260 SYN_SENT tcp 0 1 10.10.100.60:40777 10.10.9.90:3260 SYN_SENT I then went ahead and disabled all but one interface, and so as a result netstat appears to be correct, but the issue with login remains. I am positive that the target never sees a packet, because I see nothing by SYN_SENT. I know the problem is on my client, because the target is servicing multiple systems, none of which are CentOS 6.2. At this point I am pretty confident that some things changed between CentOS 6.0/6.1 and 6.2. So, if anyone have any thoughts, or ran into this, I would very much like to hear your thoughts. [root]? iscsiadm --mode node --targetname iqn.2011-12.dom.homer:01:lab-centos-servers-00001 --portal 10.10.8.90:3260,2 --interface=sw-iscsi-0 --login Logging in to [iface: sw-iscsi-0, target: iqn.2011-12.dom.homer:01:lab-centos-servers-00001, portal: 10.10.8.90,3260] (multiple) iscsiadm: Could not login to [iface: sw-iscsi-0, target: iqn.2011-12.dom.homer:01:lab-centos-servers-00001, portal: 10.10.8.90,3260]. iscsiadm: initiator reported error (8 - connection timed out) iscsiadm: Could not log into all portals [root]? netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.10.8.0 0.0.0.0 255.255.255.0 U 0 0 0 eth2.7 10.10.9.0 0.0.0.0 255.255.255.0 U 0 0 0 eth3.7 10.10.100.0 0.0.0.0 255.255.252.0 U 0 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth2 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth3 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth2.7 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth3.7 0.0.0.0 10.10.100.1 0.0.0.0 UG 0 0 0 eth0 Output of ip addr show for the two interfaces involved: [root]? for i in 2.7 3.7; do ip addr show eth$i; done 6: eth2.7@eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 00:0c:29:94:5b:8d brd ff:ff:ff:ff:ff:ff inet 10.10.8.60/24 brd 10.10.8.255 scope global eth2.7 inet6 fe80::20c:29ff:fe94:5b8d/64 scope link valid_lft forever preferred_lft forever 7: eth3.7@eth3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP link/ether 00:0c:29:94:5b:97 brd ff:ff:ff:ff:ff:ff inet 10.10.9.60/24 brd 10.10.9.255 scope global eth3.7 inet6 fe80::20c:29ff:fe94:5b97/64 scope link valid_lft forever preferred_lft forever Update 01/06/2012: This issue is getting even more interesting by the day it seems. I went a few weeks back and grabbed a snapshot of this system from before upgrading to 6.2. I spun up a new system from the snapshot, and reconfigured interface info and host keys, as well as iSCSI initiator and iscsi interface info to match new MACs. Changed nothing else. Then, I attempted to connect to my targets, and no issues at all. I cannot say that this was unexpected. I then went ahead and compared sysctl settings from both systems and there were differences after the upgrade, but nothing seemingly relevant to iSCSI or IP that could contribute to this. I also noticed that by default now two sessions per connection were enabled after the upgrade, but I changed it back to 1 session in /etc/iscsi/iscsid.conf. On the problematic system we can see that source interface is seemingly wrong, but even when I disable the 10.10.100 interface, problems persist. So, while this may be relevant, I could not validate it for certain. Needless to say, further research is necessary. Something is clearly different between releases. Working system is on 6.1, and non-working is 6.2. ::Working System:: tcp 0 0 10.10.8.210:39566 10.10.8.90:3260 ESTABLISHED tcp 0 0 10.10.9.210:46518 10.10.9.90:3260 ESTABLISHED [root]? ip route show 10.10.8.0/24 dev eth2.6 proto kernel scope link src 10.10.8.210 10.10.9.0/24 dev eth3.7 proto kernel scope link src 10.10.9.210 10.10.100.0/22 dev eth0 proto kernel scope link src 10.10.100.210 169.254.0.0/16 dev eth0 scope link metric 1002 169.254.0.0/16 dev eth2.6 scope link metric 1006 169.254.0.0/16 dev eth3.7 scope link metric 1007 default via 10.10.100.1 dev eth0 ::Non-working System:: tcp 0 1 10.10.100.60:44737 10.10.9.90:3260 SYN_SENT tcp 0 1 10.10.100.60:55479 10.10.8.90:3260 SYN_SENT [root]? ip route show 10.10.8.0/24 dev eth2.6 proto kernel scope link src 10.10.8.60 10.10.9.0/24 dev eth3.7 proto kernel scope link src 10.10.9.60 10.10.100.0/22 dev eth0 proto kernel scope link src 10.10.100.60 169.254.0.0/16 dev eth0 scope link metric 1002 169.254.0.0/16 dev eth2.6 scope link metric 1006 169.254.0.0/16 dev eth3.7 scope link metric 1007 default via 10.10.100.1 dev eth0 And the result is still same: [root]? iscsiadm: Could not login to [iface: sw-iscsi-0, target: iqn.2011-12.dom.homer:01:lab-centos-servers-00001, portal: 10.10.8.90,3260]. iscsiadm: initiator reported error (8 - connection timed out) iscsiadm: Could not login to [iface: sw-iscsi-1, target: iqn.2011-12.dom.homer:02:lab-centos-servers-00001, portal: 10.10.9.90,3260]. iscsiadm: initiator reported error (8 - connection timed out) iscsiadm: Could not log into all portals Update 01/08/2012: I believe I have been able to figure out the answer to my issue. It is quite obscure and I doubt this will happen to anyone else any time soon. It turns out that setting iface.iscsi_ifacename and iface.hwaddress in the interfaces configuration file is not legal. When one manually adds an iscsi target, such as below, all settings from the interface config file are copied into the node config file, that gets created by the below command. Result is parameters iface.iscsi_ifacename and iface.hwaddress together in the same config file. These parameters are seemingly mutually exclusive, which does not exactly make sense, or there is perhaps an oversight in the codepath. Perhaps I will investigate further. # iscsiadm -m node --op new -T iqn.2011-12.dom.homer:01:lab-centos-servers-00001 -p 10.10.8.90,3260,2 -I sw-iscsi-0 # iscsiadm -m node --op new -T iqn.2011-12.dom.homer:02:lab-centos-servers-00001 -p 10.10.9.90,3260,2 -I sw-iscsi-1 Notice, below I commented out iface.hwaddress and iface.ipaddress, after which I re-added targets, with same command as above. All works just fine. [root]? cat * # BEGIN RECORD 2.0-872.33.el6 iface.iscsi_ifacename = sw-iscsi-0 iface.net_ifacename = eth2.6 #iface.hwaddress = XX:XX:XX:XX:XX:XX #iface.ipaddress = 10.10.8.60 iface.transport_name = tcp iface.vlan_id = 6 iface.vlan_priority = 0 iface.iface_num = 0 iface.mtu = 0 iface.port = 0 # END RECORD # BEGIN RECORD 2.0-872.33.el6 iface.iscsi_ifacename = sw-iscsi-1 iface.net_ifacename = eth3.7 #iface.hwaddress = XX:XX:XX:XX:XX:XX #iface.ipaddress = 10.10.9.60 iface.transport_name = tcp iface.vlan_id = 7 iface.vlan_priority = 0 iface.iface_num = 0 iface.mtu = 0 iface.port = 0 # END RECORD Again, chances of this happening to someone else are slim to none, so likely waste of time typing this up. But, if someone does encounter this issue, I hope this post will help.

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• Diophantine Equation

  - by swapnika

  Write an iterative program that finds the largest number of McNuggets that cannot be bought in exact quantity. Your program should print the answer in the following format (where the correct number is provided in place of n): "Largest number of McNuggets that cannot be bought in exact quantity: n" Hints: Hypothesize possible instances of numbers of McNuggets that cannot be purchased exactly, starting with 1 For each possible instance, called n, 1. Test if there exists non-negative integers a, b, and c, such that 6a+9b+20c = n. (This can be done by looking at all feasible combinations of a, b, and c) 2. If not, n cannot be bought in exact quantity, save n When you have found six consecutive values of n that in fact pass the test of having an exact solution, the last answer that was saved (not the last value of n that had a solution) is the correct answer, since you know by the theorem that any amount larger can also be bought in exact quantity

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• Python-McNuggets problem

  - by challarao

  Hi! I am a student of IIIT.I am new to python.This question is one of the problems in my problem set.Please Help me writing program such as in what I should do it. Show that it is possible to buy exactly 50, 51, 52, 53, 54, and 55 McNuggets, by finding solutions to the Diophantine equation. You can solve this in your head, using paper and pencil, or writing a program. However you chose to solve this problem, list the combinations of 6, 9 and 20 packs of McNuggets you need to buy in order to get each of the exact amounts. Given that it is possible to buy sets of 50, 51, 52, 53, 54 or 55 McNuggets by combinations of 6, 9 and 20 packs, show that it is possible to buy 56, 57,..., 65 McNuggets. In other words, show how, given solutions for 50-55, one can derive solutions for 56-65 6a + 9b + 20c = n

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• BuildUrlFromExpression inside of HTML - getting 404 error from link

  - by ctote

  I'm trying to build a link that will direct the user to an MVC page when they click it. Currently I have: HTMLTable.AppendLine("<td class=\"team\"> " + tournament.TournamentRoundMatches[col][effective_match_id].competitorId1 + "<a href=\"<% =Html.BuildUrlFromExpression<CompetitionController>(c => c.Details(83)) %>\">" + " update" + "</a>" + "</td>"); But this just results in a 404 error, with the following link generated: localhost:52313/Tournament/Details/%3C%%20=Html.BuildUrlFromExpression%3CCompetitionController%3E(c%20=%3E%20c.Details(83))%20%%3E My controller method looks like this: [Authorize] public ActionResult Details(int id) { var competition = Competition.getCompetitionById(id); return View(competition); } Does anyone see what I might be doing wrong?

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• A Taxonomy of Numerical Methods v1

  - by JoshReuben

  Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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• Ubuntu Server Cannot Route to the Internet

  - by ejes

  I've been having this problem for weeks now, and I can't seem to figure out the problem. My server can route the local network and serves it well, however it cannot access the internet. It can't be the router because everything else on this lan can route through the router. I've even switched the ethernet port. Any help would be appreciated. I've tried all the usual places, anyway, here are the configs: root@uhs:~# uname -a Linux uhs 3.0.0-16-generic-pae #28-Ubuntu SMP Fri Jan 27 19:24:01 UTC 2012 i686 i686 i386 GNU/Linux root@uhs:~# cat /etc/network/interfaces # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5). # The loopback network interface auto lo iface lo inet loopback # The primary network interface # auto eth1 # iface eth1 inet dhcp auto eth0 iface eth0 inet static address 192.168.0.3 netmask 255.255.255.0 broadcast 192.168.0.255 gateway 192.168.0.1 root@uhs:~# ping -c 4 192.168.0.1 PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data. 64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=0.334 ms 64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=0.339 ms 64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=0.324 ms 64 bytes from 192.168.0.1: icmp_req=4 ttl=64 time=0.339 ms --- 192.168.0.1 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 2997ms rtt min/avg/max/mdev = 0.324/0.334/0.339/0.006 ms root@uhs:~# ping -c 4 209.85.145.103 PING 209.85.145.103 (209.85.145.103) 56(84) bytes of data. --- 209.85.145.103 ping statistics --- 4 packets transmitted, 0 received, 100% packet loss, time 3023ms root@uhs:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:0c:6e:a0:92:6e inet addr:192.168.0.3 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::20c:6eff:fea0:926e/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:13131114 errors:0 dropped:0 overruns:0 frame:0 TX packets:10540297 errors:0 dropped:0 overruns:5 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3077922794 (3.0 GB) TX bytes:3827489734 (3.8 GB) Interrupt:10 Base address:0xa000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:7721 errors:0 dropped:0 overruns:0 frame:0 TX packets:7721 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:551950 (551.9 KB) TX bytes:551950 (551.9 KB) root@uhs:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.0.1 0.0.0.0 UG 100 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 root@uhs:~# # PRETEND Traceroute root@uhs:~# for i in {1..30}; do ping -t $i -c 1 209.85.145.103; done | grep "Time to live exceeded" root@uhs:~#

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• Slow tracepath on local LAN

  - by Simone Falcini

  I am on EXSi and I have 2 instances: Ubuntu and CentOS. These are the network configurations Ubuntu eth0 Link encap:Ethernet HWaddr 00:50:56:00:1f:68 inet addr:212.83.153.71 Bcast:212.83.153.71 Mask:255.255.255.255 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:76059 errors:0 dropped:26 overruns:0 frame:0 TX packets:7224 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6482760 (6.4 MB) TX bytes:2080684 (2.0 MB) eth1 Link encap:Ethernet HWaddr 00:0c:29:46:5a:f2 inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:252 errors:0 dropped:0 overruns:0 frame:0 TX packets:608 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:42460 (42.4 KB) TX bytes:82474 (82.4 KB) /etc/iptables.conf *nat :PREROUTING ACCEPT [142:12571] :INPUT ACCEPT [5:1076] :OUTPUT ACCEPT [8:496] :POSTROUTING ACCEPT [8:496] -A POSTROUTING -s 192.168.1.0/24 -o eth0 -j MASQUERADE COMMIT *filter :INPUT ACCEPT [2:72] :FORWARD ACCEPT [4:336] :OUTPUT ACCEPT [6:328] -A INPUT -i eth1 -p tcp -j ACCEPT -A INPUT -i eth1 -p udp -j ACCEPT -A INPUT -i eth0 -p tcp --dport ssh -j ACCEPT COMMIT CentOS eth0 Link encap:Ethernet HWaddr 00:0C:29:74:1C:55 inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe74:1c55/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:499 errors:0 dropped:0 overruns:0 frame:0 TX packets:475 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:68326 (66.7 KiB) TX bytes:82641 (80.7 KiB) The main problem is that if i execute this command from the CentOS instance ssh 192.168.1.2 it takes more than 20s to connect. It seems like it's routing the connection to the wrong network. What could it be? Thanks!

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• It happens only at Devoxx ...

  - by arungupta

  After attending several Java conferences world wide, this was my very first time at Devoxx. Here are some items I found that happens only at Devoxx ... Pioneers of theater-style seating - This not only provides comfortable seating for each attendee but the screens are very clearly visible to everybody in the room. Intellectual level of attendees is very high - Read more explanation on the Java EE 6 lab blog. In short, a lab, 1/3 of the content delivered at Devoxx 2011, could not be completed at other developer days in more than 1/3 the time. Snack box for lunches - Even though this suits well to the healthy lifestyle of multiple-snacks-during-a-day style but leaves attendees hungry sooner in the day. The longer breaks before the next snack in the evening does not help at all. Fortunately, Azure cupcakes and Android ice creams turned out to be handy. I finally carried my own apple :-) Wrist band instead of lanyard - The good part about this is that once tied to your hand then you are less likely to forget in your room. But OTOH you are a pretty much a branded conference attendee all through out the city. It was cost effective as it costed 20c as opposed to 1 euro for the lanyard. Live streaming from theater #8 (the biggest room) on parleys.com All talks recorded and released on parleys.com over next year. This allows attendees to not to miss any session and watch replay at their own leisure. Stephan promised to start sharing the sessions by mid December this year. No need to pre-register for a session - This is true for most of the conferences but bigger rooms (+ overflow room for key sessions) provide sufficient space for all those who want to attend the session. And of course all sessions are available on parleys.com anyway! Community votes on whiteboard - Devoxx attendees gets a chance to vote on topics ranging from their favorite non-Java language, operating system, or love from Oracle. Captured pictures at the end of Day 2 are shown below. Movie on the last but one night - This year it was The Adventures of Tintin and was lots of fun. Fries with mayo - This is a typical Belgian thing. Guys going in ladies room to avoid the long queues ... wow! Tweet wall everywhere and I mean literally everywhere, in rooms, hallways, front desk, and other places. The tweet picking algorithm was not very clear as I never saw my tweet appear on the wall ;-) You can also watch it at wall.devoxx.com. Cozy speaker dinner with great food and wine List of parallel and upcoming sessions displayed on the screen - This makes the information more explicit with the attendees. REST API with multiple mobile clients - This API is also used by some other conferences as well. And there always is iphone.devoxx.com. Steering committee members were recognized multiple times. The committee members were clearly identifiable wearing red hoodies. The wireless SSID was intuitive "Devoxx" but hidden to avoid some crap from Microsoft Windows. All of 9000 addresses were used up most of the times with each attendee having multiple devices. A 1 GB fibre optic cable was stretched to Metropolis to support the required network bandwidth. Stephan is already planning to upgrade the equipment and have a better infrastructure next year. Free water, soda, juice in a cooler Kinect connected to TV screens so that attendees can use their hands to browse through the list of sesssions. #devoxxblog, #devoxxwomen, #devoxxfrance, #devoxxgreat, #devoxxsuggestions And Devoxx attendees are called Devoxxians ... how cool is that ? :-) What other things do you think happen only at Devoxx ? And now the pictures from the community whiteboard: And a more complete album (including bigger pics of community votes) is available below:

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• Solving Diophantine Equations Using Python

  - by HARSHITH

  In mathematics, a Diophantine equation (named for Diophantus of Alexandria, a third century Greek mathematician) is a polynomial equation where the variables can only take on integer values. Although you may not realize it, you have seen Diophantine equations before: one of the most famous Diophantine equations is: We are not certain that McDonald's knows about Diophantine equations (actually we doubt that they do), but they use them! McDonald's sells Chicken McNuggets in packages of 6, 9 or 20 McNuggets. Thus, it is possible, for example, to buy exactly 15 McNuggets (with one package of 6 and a second package of 9), but it is not possible to buy exactly 16 nuggets, since no non- negative integer combination of 6's, 9's and 20's adds up to 16. To determine if it is possible to buy exactly n McNuggets, one has to solve a Diophantine equation: find non-negative integer values of a, b, and c, such that 6a + 9b + 20c = n. Write an iterative program that finds the largest number of McNuggets that cannot be bought in exact quantity. Your program should print the answer in the following format (where the correct number is provided in place of n): "Largest number of McNuggets that cannot be bought in exact quantity: n"

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• networking through openstack installed on vm

  - by Mandar Katdare

  I am trying to set up a test installation of Openstack on a Ubuntu 12.04 VM running on a ESXi server. So far I have been able to launch the VMs on the ESXi, however am unable to assign IP addresses to them. As the VM with the Openstack installation has a single public IP, I wish to assign IPs to the VMs create through Openstack so that they can directly interact with the public network itself without having a separate private network. So I feel that bridging would not be the correct option here. But am unable to find the correct documents to go ahead with such an install. My ifconfig looks as follows: eth0 Link encap:Ethernet HWaddr 00:0c:29:6f:8a:d7 inet addr:192.168.4.167 Bcast:192.168.4.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe6f:8ad7/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:391640 errors:33 dropped:98 overruns:0 frame:0 TX packets:545044 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:40303931 (40.3 MB) TX bytes:763127348 (763.1 MB) Interrupt:18 Base address:0x2000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:146127 errors:0 dropped:0 overruns:0 frame:0 TX packets:146127 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:799815763 (799.8 MB) TX bytes:799815763 (799.8 MB) virbr0 Link encap:Ethernet HWaddr 8a:80:33:32:63:a0 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) The eth0 is the adapter that I intend to use for all communication. My nova.conf looks as follows: --dhcpbridge_flagfile=/etc/nova/nova.conf --dhcpbridge=/usr/bin/nova-dhcpbridge --logdir=/var/log/nova --state_path=/var/lib/nova --lock_path=/var/lock/nova --allow_admin_api=true --use_deprecated_auth=false --auth_strategy=keystone --scheduler_driver=nova.scheduler.simple.SimpleScheduler --s3_host=192.168.4.167 --ec2_host=192.168.4.167 --rabbit_host=192.168.4.167 --cc_host=192.168.4.167 --nova_url=http://192.168.4.167:8774/v1.1/ --routing_source_ip=192.168.4.167 --glance_api_servers=192.168.4.167:9292 --image_service=nova.image.glance.GlanceImageService --iscsi_ip_prefix=192.168.4 --sql_connection=mysql://novadbadmin:[email protected]/nova --ec2_url=http://192.168.4.167:8773/services/Cloud --keystone_ec2_url=http://192.168.4.167:5000/v2.0/ec2tokens --api_paste_config=/etc/nova/api-paste.ini --libvirt_type=kvm --libvirt_use_virtio_for_bridges=true --start_guests_on_host_boot=true --resume_guests_state_on_host_boot=true --vnc_enabled=true --vncproxy_url=http://192.168.4.167:6080 --vnc_console_proxy_url=http://192.168.4.167:6080 # network specific settings --network_manager=nova.network.manager.FlatDHCPManager --public_interface=eth0 --vmwareapi_host_ip=192.168.4.254 --vmwareapi_host_username=**** --vmwareapi_host_password=**** --vmwareapi_wsdl_loc=http://127.0.0.1:8080/wsdl/vim25/vimService.wsdl --fixed_range=192.168.4.190/24 --floating_range=192.168.4.190/24 --network_size=32 --flat_network_dhcp_start=192.168.4.190 --flat_injected=False --force_dhcp_release --iscsi_helper=tgtadm --connection_type=vmwareapi --root_helper=sudo nova-rootwrap --verbose --libvirt_use_virtio_for_bridges --ec2_private_dns_show --novnc_enabled=true --novncproxy_base_url=http://192.168.4.167:6080/vnc_auto.html --vncserver_proxyclient_address=192.168.4.167 --vncserver_listen=192.168.4.167 192.168.4.167 is my VM with the Openstack installation and 192.168.4.254 is my ESXi server on which the VM runs. Can anyone advice me about how to proceed? Thanks, Mandar

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• Linux IPTables / routing issue

  - by Jon

  Hi all, EDIT 1/3/10 22:00 GMT - rewrote some of it after further investigation It has been a while since I looked at IPtables and I seem to be worse than before as I can not seem to get my webserver online. Below is my firewall rules on the gateway server that is running the dhcp server accessing the net. The webserver is inside my network on a static IP (192.168.0.98, default port). When I use Nmap or GRC.com I see that port 80 is open on the gateway server but when I browse to it, (via public URL. http://www.houseofhawkins.com) it always fails with a connection error, (nmap cannot connect and figure out what the web server is either). I can nmap the webserver and browse to it just fine via same IP inside my network. I believe it is my IPTable rules that are not letting it through. Internally I can route all my requests. Each machine can browse to the website and traffic works just fine. I can MSTSC / ssh to all the webservers internally and they inturn can connect to the web. IPTABLE: *EDIT - Added new firewall rules 2/3/10 * #!/bin/sh iptables="/sbin/iptables" modprobe="/sbin/modprobe" depmod="/sbin/depmod" EXTIF="eth2" INTIF="eth1" load () { $depmod -a $modprobe ip_tables $modprobe ip_conntrack $modprobe ip_conntrack_ftp $modprobe ip_conntrack_irc $modprobe iptable_nat $modprobe ip_nat_ftp echo "enable forwarding.." echo "1" > /proc/sys/net/ipv4/ip_forward echo "enable dynamic addr" echo "1" > /proc/sys/net/ipv4/ip_dynaddr # start firewall # default policies $iptables -P INPUT DROP $iptables -F INPUT $iptables -P OUTPUT DROP $iptables -F OUTPUT $iptables -P FORWARD DROP $iptables -F FORWARD $iptables -t nat -F #echo " Opening loopback interface for socket based services." $iptables -A INPUT -i lo -j ACCEPT $iptables -A OUTPUT -o lo -j ACCEPT #echo " Allow all connections OUT and only existing and related ones IN" $iptables -A INPUT -i $INTIF -j ACCEPT $iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT $iptables -A OUTPUT -o $EXTIF -j ACCEPT $iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT $iptables -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT $iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT $iptables -A FORWARD -j LOG --log-level 7 --log-prefix "Dropped by firewall: " $iptables -A INPUT -j LOG --log-level 7 --log-prefix "Dropped by firewall: " $iptables -A OUTPUT -j LOG --log-level 7 --log-prefix "Dropped by firewall: " #echo " Enabling SNAT (MASQUERADE) functionality on $EXTIF" $iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE $iptables -A INPUT -i $INTIF -j ACCEPT $iptables -A OUTPUT -o $INTIF -j ACCEPT #echo " Allowing packets with ICMP data (i.e. ping)." $iptables -A INPUT -p icmp -j ACCEPT $iptables -A OUTPUT -p icmp -j ACCEPT $iptables -A INPUT -p udp -i $INTIF --dport 67 -m state --state NEW -j ACCEPT #echo " Port 137 is for NetBIOS." $iptables -A INPUT -i $INTIF -p udp --dport 137 -j ACCEPT $iptables -A OUTPUT -o $INTIF -p udp --dport 137 -j ACCEPT #echo " Opening port 53 for DNS queries." $iptables -A INPUT -p udp -i $EXTIF --sport 53 -j ACCEPT #echo " opening Apache webserver" $iptables -A PREROUTING -t nat -i $EXTIF -p tcp --dport 80 -j DNAT --to 192.168.0.96:80 $iptables -A FORWARD -p tcp -m state --state NEW -d 192.168.0.96 --dport 80 -j ACCEPT } flush () { echo "flushing rules..." $iptables -P FORWARD ACCEPT $iptables -F INPUT $iptables -P INPUT ACCEPT echo "rules flushed" } case "$1" in start|restart) flush load ;; stop) flush ;; *) echo "usage: start|stop|restart." ;; esac exit 0 route info: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 5e0412a6.bb.sky * 255.255.255.255 UH 0 0 0 eth2 192.168.0.0 * 255.255.255.0 U 0 0 0 eth1 default 5e0412a6.bb.sky 0.0.0.0 UG 100 0 0 eth2 ifconfig: eth1 Link encap:Ethernet HWaddr 00:22:b0:cf:4a:1c inet addr:192.168.0.1 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::222:b0ff:fecf:4a1c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:79023 errors:0 dropped:0 overruns:0 frame:0 TX packets:57786 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:11580918 (11.5 MB) TX bytes:22872030 (22.8 MB) Interrupt:17 Base address:0x2b00 eth2 Link encap:Ethernet HWaddr 00:0c:f1:7c:45:5b inet addr:94.4.18.166 Bcast:94.4.18.166 Mask:255.255.255.255 inet6 addr: fe80::20c:f1ff:fe7c:455b/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:57038 errors:0 dropped:0 overruns:0 frame:0 TX packets:34532 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:21631721 (21.6 MB) TX bytes:7685444 (7.6 MB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:16 errors:0 dropped:0 overruns:0 frame:0 TX packets:16 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1517 (1.5 KB) TX bytes:1517 (1.5 KB) EDIT OK so as requested I will try and expand on my infrastructure: I previously had it setup with a Sky broadband modem router that did the DHCP and I used its web interface to port forward the web across to the web server. The network looked something like this: I have now replaced the sky modem with a dlink modem which gives the IP to the gateway server that now does the DHCP. It looks like: The internet connection is a standard broadband connection with a dynamic IP, (use zoneedit.com to keep it updated). I have tried it on each of the webservers(one Ubuntu Apache server and one WS2008 IIS7). I think there must also be an issue with my IPTable rules as it can route to my win7 box which has the default IIS7 page and that would not display when I forwarded all port 80 to it. I would be really grateful for any and all help with this. Thanks Jon

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• SVN Server not responding

  - by Rob Forrest

  I've been bashing my head against a wall with this one all day and I would greatly appreciate a few more eyes on the problem at hand. We have an in-house SVN Server that contains all live and development code for our website. Our live server can connect to this and get updates from the repository. This was all working fine until we migrated the SVN Server from a physical machine to a vSphere VM. Now, for some reason that continues to fathom me, we can no longer connect to the SVN Server. The SVN Server runs CentOS 6.2, Apache and SVN 1.7.2. SELinux is well and trully disabled and the problem remains when iptables is stopped. Our production server does run an older version of CentOS and SVN but the same system worked previously so I don't think that this is the issue. Of note, if I have iptables enabled, using service iptables status, I can see a single packet coming in and being accepted but the production server simply hangs on any svn command. If I give up waiting and do a CTRL-C to break the process I get a "could not connect to server". To me it appears to be something to do with the SVN Server rejecting external connections but I have no idea how this would happen. Any thoughts on what I can try from here? Thanks, Rob Edit: Network topology Production server sits externally to our in-house SVN server. Our IPCop (?) firewall allows connections from it (and it alone) on port 80 and passes the connection to the SVN Server. The hardware is all pretty decent and I don't doubt that its doing its job correctly, especially as iptables is seeing the new connections. subversion.conf (in /etc/httpd/conf.d) LoadModule dav_svn_module modules/mod_dav_svn.so <Location /repos> DAV svn SVNPath /var/svn/repos <LimitExcept PROPFIND OPTIONS REPORT> AuthType Basic AuthName "SVN Server" AuthUserFile /var/svn/svn-auth Require valid-user </LimitExcept> </Location> ifconfig eth0 Link encap:Ethernet HWaddr 00:0C:29:5F:C8:3A inet addr:172.16.0.14 Bcast:172.16.0.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe5f:c83a/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:32317 errors:0 dropped:0 overruns:0 frame:0 TX packets:632 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2544036 (2.4 MiB) TX bytes:143207 (139.8 KiB) netstat -lntp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 1484/mysqld tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 1135/rpcbind tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1351/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1230/cupsd tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1575/master tcp 0 0 0.0.0.0:58401 0.0.0.0:* LISTEN 1153/rpc.statd tcp 0 0 0.0.0.0:5672 0.0.0.0:* LISTEN 1626/qpidd tcp 0 0 :::139 :::* LISTEN 1678/smbd tcp 0 0 :::111 :::* LISTEN 1135/rpcbind tcp 0 0 :::80 :::* LISTEN 1615/httpd tcp 0 0 :::22 :::* LISTEN 1351/sshd tcp 0 0 ::1:631 :::* LISTEN 1230/cupsd tcp 0 0 ::1:25 :::* LISTEN 1575/master tcp 0 0 :::445 :::* LISTEN 1678/smbd tcp 0 0 :::56799 :::* LISTEN 1153/rpc.statd iptables --list -v -n (when iptables is stopped) Chain INPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination iptables --list -v -n (when iptables is running, after one attempted svn connection) Chain INPUT (policy ACCEPT 68 packets, 6561 bytes) pkts bytes target prot opt in out source destination 19 1304 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0 0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 1 60 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:80 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:80 0 0 ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW udp dpt:80 Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 17 packets, 1612 bytes) pkts bytes target prot opt in out source destination tcpdump 17:08:18.455114 IP 'production server'.43255 > 'svn server'.local.http: Flags [S], seq 3200354543, win 5840, options [mss 1380,sackOK,TS val 2011458346 ecr 0,nop,wscale 7], length 0 17:08:18.455169 IP 'svn server'.local.http > 'production server'.43255: Flags [S.], seq 629885453, ack 3200354544, win 14480, options [mss 1460,sackOK,TS val 816478 ecr 2011449346,nop,wscale 7], length 0 17:08:19.655317 IP 'svn server'.local.http > 'production server'k.43255: Flags [S.], seq 629885453, ack 3200354544, win 14480, options [mss 1460,sackOK,TS val 817679 ecr 2011449346,nop,wscale 7], length 0

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• Linux - Only first virtual interface can ping external gateway

  - by husvar

  I created 3 virtual interfaces with different mac addresses all linked to the same physical interface. I see that they successfully arp for the gw and they can ping (the request is coming in the packet capture in wireshark). However the ping utility does not count the responses. Does anyone knows the issue? I am running Ubuntu 14.04 in a VmWare. root@ubuntu:~# ip link sh 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 link/ether 00:0c:29:bc:fc:8b brd ff:ff:ff:ff:ff:ff root@ubuntu:~# ip addr sh 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:0c:29:bc:fc:8b brd ff:ff:ff:ff:ff:ff inet6 fe80::20c:29ff:febc:fc8b/64 scope link valid_lft forever preferred_lft forever root@ubuntu:~# ip route sh root@ubuntu:~# ip link add link eth0 eth0.1 addr 00:00:00:00:00:11 type macvlan root@ubuntu:~# ip link add link eth0 eth0.2 addr 00:00:00:00:00:22 type macvlan root@ubuntu:~# ip link add link eth0 eth0.3 addr 00:00:00:00:00:33 type macvlan root@ubuntu:~# ip -4 link sh 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 link/ether 00:0c:29:bc:fc:8b brd ff:ff:ff:ff:ff:ff 18: eth0.1@eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default link/ether 00:00:00:00:00:11 brd ff:ff:ff:ff:ff:ff 19: eth0.2@eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default link/ether 00:00:00:00:00:22 brd ff:ff:ff:ff:ff:ff 20: eth0.3@eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default link/ether 00:00:00:00:00:33 brd ff:ff:ff:ff:ff:ff root@ubuntu:~# ip -4 addr sh 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever root@ubuntu:~# ip -4 route sh root@ubuntu:~# dhclient -v eth0.1 Internet Systems Consortium DHCP Client 4.2.4 Copyright 2004-2012 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Listening on LPF/eth0.1/00:00:00:00:00:11 Sending on LPF/eth0.1/00:00:00:00:00:11 Sending on Socket/fallback DHCPDISCOVER on eth0.1 to 255.255.255.255 port 67 interval 3 (xid=0x568eac05) DHCPREQUEST of 192.168.1.145 on eth0.1 to 255.255.255.255 port 67 (xid=0x568eac05) DHCPOFFER of 192.168.1.145 from 192.168.1.254 DHCPACK of 192.168.1.145 from 192.168.1.254 bound to 192.168.1.145 -- renewal in 1473 seconds. root@ubuntu:~# dhclient -v eth0.2 Internet Systems Consortium DHCP Client 4.2.4 Copyright 2004-2012 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Listening on LPF/eth0.2/00:00:00:00:00:22 Sending on LPF/eth0.2/00:00:00:00:00:22 Sending on Socket/fallback DHCPDISCOVER on eth0.2 to 255.255.255.255 port 67 interval 3 (xid=0x21e3114e) DHCPREQUEST of 192.168.1.146 on eth0.2 to 255.255.255.255 port 67 (xid=0x21e3114e) DHCPOFFER of 192.168.1.146 from 192.168.1.254 DHCPACK of 192.168.1.146 from 192.168.1.254 bound to 192.168.1.146 -- renewal in 1366 seconds. root@ubuntu:~# dhclient -v eth0.3 Internet Systems Consortium DHCP Client 4.2.4 Copyright 2004-2012 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Listening on LPF/eth0.3/00:00:00:00:00:33 Sending on LPF/eth0.3/00:00:00:00:00:33 Sending on Socket/fallback DHCPDISCOVER on eth0.3 to 255.255.255.255 port 67 interval 3 (xid=0x11dc5f03) DHCPREQUEST of 192.168.1.147 on eth0.3 to 255.255.255.255 port 67 (xid=0x11dc5f03) DHCPOFFER of 192.168.1.147 from 192.168.1.254 DHCPACK of 192.168.1.147 from 192.168.1.254 bound to 192.168.1.147 -- renewal in 1657 seconds. root@ubuntu:~# ip -4 link sh 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000 link/ether 00:0c:29:bc:fc:8b brd ff:ff:ff:ff:ff:ff 18: eth0.1@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default link/ether 00:00:00:00:00:11 brd ff:ff:ff:ff:ff:ff 19: eth0.2@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default link/ether 00:00:00:00:00:22 brd ff:ff:ff:ff:ff:ff 20: eth0.3@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default link/ether 00:00:00:00:00:33 brd ff:ff:ff:ff:ff:ff root@ubuntu:~# ip -4 addr sh 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever 18: eth0.1@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default inet 192.168.1.145/24 brd 192.168.1.255 scope global eth0.1 valid_lft forever preferred_lft forever 19: eth0.2@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default inet 192.168.1.146/24 brd 192.168.1.255 scope global eth0.2 valid_lft forever preferred_lft forever 20: eth0.3@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default inet 192.168.1.147/24 brd 192.168.1.255 scope global eth0.3 valid_lft forever preferred_lft forever root@ubuntu:~# ip -4 route sh default via 192.168.1.254 dev eth0.1 192.168.1.0/24 dev eth0.1 proto kernel scope link src 192.168.1.145 192.168.1.0/24 dev eth0.2 proto kernel scope link src 192.168.1.146 192.168.1.0/24 dev eth0.3 proto kernel scope link src 192.168.1.147 root@ubuntu:~# arping -c 5 -I eth0.1 192.168.1.254 ARPING 192.168.1.254 from 192.168.1.145 eth0.1 Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 6.936ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 2.986ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 0.654ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 5.137ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 2.426ms Sent 5 probes (1 broadcast(s)) Received 5 response(s) root@ubuntu:~# arping -c 5 -I eth0.2 192.168.1.254 ARPING 192.168.1.254 from 192.168.1.146 eth0.2 Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 5.665ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 3.753ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 16.500ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 3.287ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 32.438ms Sent 5 probes (1 broadcast(s)) Received 5 response(s) root@ubuntu:~# arping -c 5 -I eth0.3 192.168.1.254 ARPING 192.168.1.254 from 192.168.1.147 eth0.3 Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 4.422ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 2.429ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 2.321ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 40.423ms Unicast reply from 192.168.1.254 [58:98:35:57:a0:70] 2.268ms Sent 5 probes (1 broadcast(s)) Received 5 response(s) root@ubuntu:~# tcpdump -n -i eth0.1 -v & [1] 5317 root@ubuntu:~# ping -c5 -q -I eth0.1 192.168.1.254 PING 192.168.1.254 (192.168.1.254) from 192.168.1.145 eth0.1: 56(84) bytes of data. tcpdump: listening on eth0.1, link-type EN10MB (Ethernet), capture size 65535 bytes 13:18:37.612558 IP (tos 0x0, ttl 64, id 2595, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.145 > 192.168.1.254: ICMP echo request, id 5318, seq 2, length 64 13:18:37.618864 IP (tos 0x68, ttl 64, id 14493, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.145: ICMP echo reply, id 5318, seq 2, length 64 13:18:37.743650 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.87 tell 192.168.1.86, length 46 13:18:38.134997 IP (tos 0x0, ttl 128, id 23547, offset 0, flags [none], proto UDP (17), length 229) 192.168.1.86.138 > 192.168.1.255.138: NBT UDP PACKET(138) 13:18:38.614580 IP (tos 0x0, ttl 64, id 2596, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.145 > 192.168.1.254: ICMP echo request, id 5318, seq 3, length 64 13:18:38.793479 IP (tos 0x68, ttl 64, id 14495, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.145: ICMP echo reply, id 5318, seq 3, length 64 13:18:39.151282 IP6 (class 0x68, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::5a98:35ff:fe57:e070 > ff02::1:ff6b:e9b4: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2001:818:d812:da00:8ae3:abff:fe6b:e9b4 source link-address option (1), length 8 (1): 58:98:35:57:a0:70 13:18:39.615612 IP (tos 0x0, ttl 64, id 2597, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.145 > 192.168.1.254: ICMP echo request, id 5318, seq 4, length 64 13:18:39.746981 IP (tos 0x68, ttl 64, id 14496, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.145: ICMP echo reply, id 5318, seq 4, length 64 --- 192.168.1.254 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4008ms rtt min/avg/max/mdev = 2.793/67.810/178.934/73.108 ms root@ubuntu:~# killall tcpdump >> /dev/null 2>&1 9 packets captured 12 packets received by filter 0 packets dropped by kernel [1]+ Done tcpdump -n -i eth0.1 -v root@ubuntu:~# tcpdump -n -i eth0.2 -v & [1] 5320 root@ubuntu:~# ping -c5 -q -I eth0.2 192.168.1.254 PING 192.168.1.254 (192.168.1.254) from 192.168.1.146 eth0.2: 56(84) bytes of data. tcpdump: listening on eth0.2, link-type EN10MB (Ethernet), capture size 65535 bytes 13:18:41.536874 ARP, Ethernet (len 6), IPv4 (len 4), Reply 192.168.1.254 is-at 58:98:35:57:a0:70, length 46 13:18:41.536933 IP (tos 0x0, ttl 64, id 2599, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.146 > 192.168.1.254: ICMP echo request, id 5321, seq 1, length 64 13:18:41.539255 IP (tos 0x68, ttl 64, id 14507, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.146: ICMP echo reply, id 5321, seq 1, length 64 13:18:42.127715 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.87 tell 192.168.1.86, length 46 13:18:42.511725 IP (tos 0x0, ttl 64, id 2600, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.146 > 192.168.1.254: ICMP echo request, id 5321, seq 2, length 64 13:18:42.514385 IP (tos 0x68, ttl 64, id 14527, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.146: ICMP echo reply, id 5321, seq 2, length 64 13:18:42.743856 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.87 tell 192.168.1.86, length 46 13:18:43.511727 IP (tos 0x0, ttl 64, id 2601, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.146 > 192.168.1.254: ICMP echo request, id 5321, seq 3, length 64 13:18:43.513768 IP (tos 0x68, ttl 64, id 14528, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.146: ICMP echo reply, id 5321, seq 3, length 64 13:18:43.637598 IP (tos 0x0, ttl 128, id 23551, offset 0, flags [none], proto UDP (17), length 225) 192.168.1.86.17500 > 255.255.255.255.17500: UDP, length 197 13:18:43.641185 IP (tos 0x0, ttl 128, id 23552, offset 0, flags [none], proto UDP (17), length 225) 192.168.1.86.17500 > 192.168.1.255.17500: UDP, length 197 13:18:43.641201 IP (tos 0x0, ttl 128, id 23553, offset 0, flags [none], proto UDP (17), length 225) 192.168.1.86.17500 > 255.255.255.255.17500: UDP, length 197 13:18:43.743890 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.87 tell 192.168.1.86, length 46 13:18:44.510758 IP (tos 0x0, ttl 64, id 2602, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.146 > 192.168.1.254: ICMP echo request, id 5321, seq 4, length 64 13:18:44.512892 IP (tos 0x68, ttl 64, id 14538, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.146: ICMP echo reply, id 5321, seq 4, length 64 13:18:45.510794 IP (tos 0x0, ttl 64, id 2603, offset 0, flags [DF], proto ICMP (1), length 84) 192.168.1.146 > 192.168.1.254: ICMP echo request, id 5321, seq 5, length 64 13:18:45.519701 IP (tos 0x68, ttl 64, id 14539, offset 0, flags [none], proto ICMP (1), length 84) 192.168.1.254 > 192.168.1.146: ICMP echo reply, id 5321, seq 5, length 64 13:18:49.287554 IP6 (class 0x68, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::5a98:35ff:fe57:e070 > ff02::1:ff6b:e9b4: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2001:818:d812:da00:8ae3:abff:fe6b:e9b4 source link-address option (1), length 8 (1): 58:98:35:57:a0:70 13:18:50.013463 IP (tos 0x0, ttl 255, id 50737, offset 0, flags [DF], proto UDP (17), length 73) 192.168.1.146.5353 > 224.0.0.251.5353: 0 [2q] PTR (QM)? _ipps._tcp.local. PTR (QM)? _ipp._tcp.local. (45) 13:18:50.218874 IP6 (class 0x68, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::5a98:35ff:fe57:e070 > ff02::1:ff6b:e9b4: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2001:818:d812:da00:8ae3:abff:fe6b:e9b4 source link-address option (1), length 8 (1): 58:98:35:57:a0:70 13:18:51.129961 IP6 (class 0x68, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::5a98:35ff:fe57:e070 > ff02::1:ff6b:e9b4: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2001:818:d812:da00:8ae3:abff:fe6b:e9b4 source link-address option (1), length 8 (1): 58:98:35:57:a0:70 13:18:52.197074 IP6 (hlim 255, next-header UDP (17) payload length: 53) 2001:818:d812:da00:200:ff:fe00:22.5353 > ff02::fb.5353: [udp sum ok] 0 [2q] PTR (QM)? _ipps._tcp.local. PTR (QM)? _ipp._tcp.local. (45) 13:18:54.128240 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.87 tell 192.168.1.86, length 46 --- 192.168.1.254 ping statistics --- 5 packets transmitted, 0 received, 100% packet loss, time 4000ms root@ubuntu:~# killall tcpdump >> /dev/null 2>&1 13:18:54.657731 IP6 (class 0x68, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::5a98:35ff:fe57:e070 > ff02::1:ff6b:e9b4: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2001:818:d812:da00:8ae3:abff:fe6b:e9b4 source link-address option (1), length 8 (1): 58:98:35:57:a0:70 13:18:54.743174 ARP, Ethernet (len 6), IPv4 (len 4), Request who-has 192.168.1.87 tell 192.168.1.86, length 46 25 packets captured 26 packets received by filter 0 packets dropped by kernel [1]+ Done tcpdump -n -i eth0.2 -v root@ubuntu:~# tcpdump -n -i eth0.3 icmp & [1] 5324 root@ubuntu:~# ping -c5 -q -I eth0.3 192.168.1.254 PING 192.168.1.254 (192.168.1.254) from 192.168.1.147 eth0.3: 56(84) bytes of data. tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0.3, link-type EN10MB (Ethernet), capture size 65535 bytes 13:18:56.373434 IP 192.168.1.147 > 192.168.1.254: ICMP echo request, id 5325, seq 1, length 64 13:18:57.372116 IP 192.168.1.147 > 192.168.1.254: ICMP echo request, id 5325, seq 2, length 64 13:18:57.381263 IP 192.168.1.254 > 192.168.1.147: ICMP echo reply, id 5325, seq 2, length 64 13:18:58.371141 IP 192.168.1.147 > 192.168.1.254: ICMP echo request, id 5325, seq 3, length 64 13:18:58.373275 IP 192.168.1.254 > 192.168.1.147: ICMP echo reply, id 5325, seq 3, length 64 13:18:59.371165 IP 192.168.1.147 > 192.168.1.254: ICMP echo request, id 5325, seq 4, length 64 13:18:59.373259 IP 192.168.1.254 > 192.168.1.147: ICMP echo reply, id 5325, seq 4, length 64 13:19:00.371211 IP 192.168.1.147 > 192.168.1.254: ICMP echo request, id 5325, seq 5, length 64 13:19:00.373278 IP 192.168.1.254 > 192.168.1.147: ICMP echo reply, id 5325, seq 5, length 64 --- 192.168.1.254 ping statistics --- 5 packets transmitted, 1 received, 80% packet loss, time 4001ms rtt min/avg/max/mdev = 13.666/13.666/13.666/0.000 ms root@ubuntu:~# killall tcpdump >> /dev/null 2>&1 9 packets captured 10 packets received by filter 0 packets dropped by kernel [1]+ Done tcpdump -n -i eth0.3 icmp root@ubuntu:~# arp -n Address HWtype HWaddress Flags Mask Iface 192.168.1.254 ether 58:98:35:57:a0:70 C eth0.1 192.168.1.254 ether 58:98:35:57:a0:70 C eth0.2 192.168.1.254 ether 58:98:35:57:a0:70 C eth0.3

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