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• Cannot run a VM with more than three network interfaces with KVM

  - by Bostonvaulter

  I'm running KVM on top of Ubuntu 10.10 Server I can create VM's (Virtual Machine) and network interfaces fine but I cannot seem to add more than three network interfaces. As soon as I have a VM with four network interfaces it gets stuck on startup at the starting SeaBIOS page with this message: Starting SeaBIOS (version pre-0.6.1-20100702_143500-palmer) So far I've verified this with two VM's, a Ubuntu 10.10 desktop and a Vyatta router. The specific network hardware I assign to the VM's doesn't seem to matter. I'm trying to have one bridged interface and three private networks using Vyatta to route between them. Does anyone know why I can't run a VM with more than three network interfaces? Edit: Additionally the KVM thread responsible for the specific VM hangs using ~100% CPU (i.e. one core). Here's the command for the process that is hanging: /usr/bin/kvm -S -M pc-0.12 -enable-kvm -m 512 -smp 1,sockets=1,cores=1,threads=1 -name vyatta -uuid 6dff7c94-6810-423e-5fea-fec10da0e9b7 -nodefaults -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/vyatta.monitor,server,nowait -mon chardev=monitor,mode=readline -rtc base=utc -boot c -drive file=/home/rams/virtual-machines/vyatta.img,if=none,id=drive-ide0-0-0,boot=on,format=raw -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -drive if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -device rtl8139,vlan=0,id=net0,mac=00:54:00:be:cc:4b,bus=pci.0,addr=0x3 -net tap,fd=97,vlan=0,name=hostnet0 -device rtl8139,vlan=1,id=net1,mac=52:54:00:da:59:ed,bus=pci.0,addr=0x5 -net tap,fd=98,vlan=1,name=hostnet1 -device rtl8139,vlan=2,id=net2,mac=52:54:00:ce:22:b6,bus=pci.0,addr=0x6 -net tap,fd=99,vlan=2,name=hostnet2 -device rtl8139,vlan=3,id=net3,mac=52:54:00:1e:bc:46,bus=pci.0,addr=0x7 -net tap,fd=101,vlan=3,name=hostnet3 -chardev pty,id=serial0 -device isa-serial,chardev=serial0 -usb -vnc 127.0.0.1:0 -k en-us -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 Edit: I've also found an error in dmesg that might be related (it also shows up when running virtd in verbose mode): 14:47:24.399: warning : qemudParsePCIDeviceStrs:1422 : Unexpected exit status '1', qemu probably failed I've also tried disabling app armor but that doesn't seem to make a difference.

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• iptables DNS resolution

  - by Favolas

  I have a virtual machine with Fedora 19 acting as a router. This machine as an interface (p8p1) with the IP 172.16.1.254 that is connected to another machine (IP 172.16.1.1) that's simulating the external network. I've installed snort 2.9.2.2, applied the snortsam-2.9.2.2.diff.gz patch and installed snortsam 2.70 on the routermachine In snort.conf besides altering some RULE_PATH I believe I've only added the following line to the file. output alert_fwsam: 127.0.0.1:898/password After doing this two comands: ifconfig p8p1 promisc /usr/local/snort/bin/snort -v -i p8p1 If I ping from the external network to the router IP, I can see the info about the pings. One of the rules that I have is icmp-info.rules that as this single line: alert icmp $EXTERNAL_NET any -> $HOME_NET any (msg:"ICMP-INFO Echo Reply"; icode:0; itype:0; classtype:misc-activity; sid:408; rev:6;fwsam: src, 5 minutes;) snortsam.conf as this data: defaultkey password accept localhost keyinterval 30 minutes dontblock 192.168.1.1 # rede local rollbackhosts 50 rollbackthreshold 20 / 30 secs rollbacksleeptime 1 minute logfile /var/log/snort/snortsam.log loglevel 3 daemon nothreads # linha importante para gerar os bloqueios via iptables iptables p8p1 LOG bindip 127.0.0.1 Now I run this command: /usr/local/snort/bin/snort -u snort -i p8p1 -c /etc/snort/snort.conf -l /var/log/snort -Dq Terminal gives this message: Spawning daemon child... My daemon child 2080 lives... Daemon parent exiting (0) and when I runsnortsam in terminal i got this: SnortSam, v 2.70. Copyright (c) 2001-2009 Frank Knobbe . All rights reserved. Plugin 'fwsam': v 2.5, by Frank Knobbe Plugin 'fwexec': v 2.7, by Frank Knobbe Plugin 'pix': v 2.9, by Frank Knobbe Plugin 'ciscoacl': v 2.12, by Ali Basel <[email protected]> Plugin 'cisconullroute': v 2.5, by Frank Knobbe Plugin 'cisconullroute2': v 2.2, by Wouter de Jong <[email protected]> Plugin 'netscreen': v 2.10, by Frank Knobbe Plugin 'ipchains': v 2.8, by Hector A. Paterno <[email protected]> Plugin 'iptables': v 2.9, by Fabrizio Tivano <[email protected]>, Luis Marichal <[email protected]> Plugin 'ebtables': v 2.4, by Bruno Scatolin <[email protected]> Plugin 'watchguard': v 2.7, by Thomas Maier <[email protected]> Plugin 'email': v 2.12, by Frank Knobbe Plugin 'email-blocks-only': v 2.12, by Frank Knobbe Plugin 'snmpinterfacedown': v 2.3, by Ali BASEL <[email protected]> Plugin 'forward': v 2.8, by Frank Knobbe Parsing config file /etc/snortsam.conf... Linking plugin 'iptables'... Checking for existing state file "/var/db/snortsam.state". Found. Reading state file. Starting to listen for Snort alerts. and snortsam.log as an entry like this 2013/10/25, 10:15:17, -, 1, snortsam, Starting to listen for Snort alerts. Now, from the external machine I do ping 172.16.1.254 and it starts showing the info and an alert file is created in /var/log/snort/ that as the info about the PINGS. Something like: [**] [1:408:6] ICMP-INFO Echo Reply [**] [Classification: Misc activity] [Priority: 3] 10/25-10:35:16.061319 172.16.1.254 -> 172.16.1.1 ICMP TTL:64 TOS:0x0 ID:38720 IpLen:20 DgmLen:84 Type:0 Code:0 ID:1389 Seq:1 ECHO REPLY Also, if I run instead /usr/local/snort/bin/snort snort -v -i p8p1 i got this message: Running in packet dump mode --== Initializing Snort ==-- Initializing Output Plugins! Snort BPF option: snort pcap DAQ configured to passive. The DAQ version does not support reload. Acquiring network traffic from "p8p1". ERROR: Can't set DAQ BPF filter to 'snort' (pcap_daq_set_filter: pcap_compile: syntax error)! Fatal Error, Quitting.. So, this are my questions: Shouldn't snortsam block the PING? Is that DAQ error causing the problem? If so, How can I solve it?

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• How to know my wireless card has injection enabled?

  - by shrimpy

  I am playing around with aircrack. And was trying to see whether my wireless card on my laptop can pass the injection test And I end up seeing the following... does it mean my wireless card is not able to run aircrack? root@myubuntu:/home/myubuntu# iwconfig lo no wireless extensions. eth0 no wireless extensions. eth1 IEEE 802.11bg ESSID:"" Nickname:"" Mode:Managed Frequency:2.437 GHz Access Point: Not-Associated Bit Rate:54 Mb/s Tx-Power:24 dBm Retry min limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=5/5 Signal level=0 dBm Noise level=-57 dBm Rx invalid nwid:0 Rx invalid crypt:781 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 root@myubuntu:/home/myubuntu# aireplay-ng -9 eth1 ioctl(SIOCSIWMODE) failed: Invalid argument ARP linktype is set to 1 (Ethernet) - expected ARPHRD_IEEE80211, ARPHRD_IEEE80211_FULL or ARPHRD_IEEE80211_PRISM instead. Make sure RFMON is enabled: run 'airmon-ng start eth1 <#>' Sysfs injection support was not found either. root@myubuntu:/home/myubuntu#

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• TIME_WAIT connections not being cleaned up after timeout period expires

  - by Mark Dawson

  I am stress testing one of my servers by hitting it with a constant stream of new network connections, the tcp_fin_timeout is set to 60, so if I send a constant stream of something like 100 requests per second, I would expect to see a rolling average of 6000 (60 * 100) connections in a TIME_WAIT state, this is happening, but looking in netstat (using -o) to see the timers, I see connections like: TIME_WAIT timewait (0.00/0/0) where their timeout has expired but the connection is still hanging around, I then eventually run out of connections. Anyone know why these connections don't get cleaned up? If I stop creating new connections they do eventually disappear but while I am constantly creating new connections they don't, seems like the kernel isn't getting chance to clean them up? Is there some other config options I need to set to remove the connections as soon as they have expired? The server is running Ubuntu and my web server is nginx. Also it has iptables with connection tracking, not sure if that would cause these TIME_WAIT connections to live on. Thanks Mark.

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• Ensuring a repeatable directory ordering in linux

  - by Paul Biggar

  I run a hosted continuous integration company, and we run our customers' code on Linux. Each time we run the code, we run it in a separate virtual machine. A frequent problem that arises is that a customer's tests will sometimes fail because of the directory ordering of their code checked out on the VM. Let me go into more detail. On OSX, the HFS+ file system ensures that directories are always traversed in the same order. Programmers who use OSX assume that if it works on their machine, it must work everywhere. But it often doesn't work on Linux, because linux file systems do not offer ordering guarantees when traversing directories. As an example, consider there are 2 files, a.rb, b.rb. a.rb defines MyObject, and b.rb uses MyObject. If a.rb is loaded first, everything will work. If b.rb is loaded first, it will try to access an undefined variable MyObject, and fail. But worse than this, is that it doesn't always just fail. Because the file system ordering on Linux is not ordered, it will be a different order on different machines. This is worse because sometimes the tests pass, and sometimes they fail. This is the worst possible result. So my question is, is there a way to make file system ordering repeatable. Some flag to ext4 perhaps, that says it will always traverse directories in some order? Or maybe a different file system that has this guarantee?

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• Duplicate IP address detection with multiple NICs

  - by sfink

  I am using arping -D to detect duplicate IP addresses within a network when setting up servers. (The network is controlled by someone else, and we have had many issues with IP allocation in the past.) It works fine as long as my host has a single NIC on a given VLAN, but when my host has more than one (I have one with 9 NICs on one VLAN and 1 on the other), arping -D always returns false collisions. The problem is that all 9 of my NICs respond to an ARP request for any of the IPs on those NICs. (These are real physical NICs, not aliases or anything.) I send out one ARP request packet, and get 9 ARP is-at ARP replies, one for each MAC address. I could implement my own solution by sniffing packets and checking for any replies with a MAC address other than the local NICs', but it seems like there ought to be an easier way.

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• Forward all tracif from one IP to another Ip on OS X

  - by Josh

  This is related to this question I just asked... I have two IP address on my iMac I want to "bridge". I'm not sure what the proper terminology is... here's the situation. My iMac has a firewire connection to my laptop and an ethernet connection to the rest of my office. My laptop has an ip of 192.168.100.2 (on the firewire interface). My iMac has an IP of 192.168.100.1 on the firewire interface, and two IPs, 10.1.0.6 and 10.1.0.7, on it's ethernet interface. If I wanted to forward all traffic coming in from 192.168.100.2 on my OS X machine to go out on IP 10.1.0.7, and vice-versa, can this be done? I assume I would use the ipfw command. Essentially I want to "bridge" the firewire network to the ethernet network so my laptop can see all the machines on the 10.1 network, and all those machines can see my laptop at 10.1.0.7. Is this possible?

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• Network is going down once per day

  - by Charly

  Once per day the network on eth0 is going down and we need to do sudo ifdown eth0; sudo ifup eth0 to get the network up. Here is the syslog: Feb 11 12:48:01 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 12:52:35 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 12:56:23 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:00:28 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:04:29 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:09:16 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:13:53 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:18:16 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:22:25 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:26:52 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:30:44 www-tech-1 dhclient: DHCPREQUEST of address> on eth0 to 131.121.113.228 port 67 Feb 11 13:31:49 www-tech-1 dhclient: There is already a pid file /var/run/dhclient.eth0.pid with pid 3198 Feb 11 13:31:49 www-tech-1 dhclient: Listening on LPF/eth0/00:e0:81:49:fc:e0 Feb 11 13:31:49 www-tech-1 dhclient: Sending on LPF/eth0/00:e0:81:49:fc:e0 Feb 11 13:31:49 www-tech-1 dhclient: DHCPRELEASE on eth0 to 131.121.113.228 port 67 Feb 11 13:31:49 www-tech-1 dhclient: There is already a pid file /var/run/dhclient.eth0.pid with pid 134519072 Feb 11 13:31:50 www-tech-1 dhclient: Listening on LPF/eth0/00:e0:81:49:fc:e0 Feb 11 13:31:50 www-tech-1 dhclient: Sending on LPF/eth0/00:e0:81:49:fc:e0 Feb 11 13:31:52 www-tech-1 dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8 Feb 11 13:31:52 www-tech-1 dhclient: DHCPREQUEST of 131.121.14.17 on eth0 to 255.255.255.255 port 67 Feb 11 13:31:53 www-tech-1 kernel: [265383.991682] eth0: no IPv6 routers present Please check the last portion of this syslog. Can anybody help me?

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• Cent OS ifcfg configuration for ranges of IP's with different netmask

  - by Aaron Schlegel

  I have 1 set of 30 public IP's with a netmask of 255.255.255.0 and another set of 30 IP's with a netmask of 255.255.255.128. Both sets of IP's also have different gateways. How can I virtually assign the IP's to the machine? I have tried creating ifcfg-eth0:0 ifcfg-eth0:1 ifcfg-eth0:X ect for each IP. Below is my ifcfg file with. I have this for each IP with the correct gateway IP and netmask for each of my 60 IP's. If I do ip addr show it does show all of the 60 addresses with the correct broadcast IP and netmask. However I can only use 30 of my IP's that are from the same netmask. Am I doing this correctly? If the IP's show up with ip addr show does that mean I have correctly assigned them to the machine virtually? I want to check before I blame my hosting company for not routing the IP's correctly. DEVICE="eth0:1" BOOTPROTO="static" DNS1="**.**.**.**" DNS2="**.**.**.**" GATEWAY="2**.**.***.126" HOSTNAME="localhost.localdomain" HWADDR="0*:19:**:**:**:**" IPADDR="2**.*.**.**" IPV6INIT="no" MTU="1500" NETMASK="255.255.255.128" NM_CONTROLLED="yes" ONBOOT="yes" TYPE="Ethernet" Also is there a better way to do this? I have used ifcfg-eth0:0-range1 before to assign a range of IP's from the same netmask. Is it possible to do this with ranges with different netmask? Thanks!

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• Default route not on LAN

  - by jarmund

  I have a network that in principle looks like this: H1---\ /----Inet1 H2---->---GW1---< H3---/ \----GW2-----Inet2 H1 and H2 = Hosts that need access to internet with GW1 Inet1 = Internet link over 3G connection Inet2 = 5GHz link to Internet (not always up) GW1 = Works as a router, automatically picking the "best" connection between Inet1 and Inet2 (the latter via GW2). GW2 = 5GHz wifi router And here's the problem: H3 only needs internet access when Inet2 is up. What i was thinking of doing was a routing table that looks like this: route to GW2 via GW1 default route is via GW2 I first set the route to GW2 via GW1 without a problem. But when i try route add default gw 1.2.3.4 (1.2.3.4 being the IP of GW2), it complains "SIOCADDRT: No such device" Is the problem that the default gw i'm trying to set is not reachable directly? Is there a different approach that would allow me to achieve this? An alternative (and hypothetical) approach: Since H3 will be using a static IP, is it possible to do some magic with iptables on GW1 to forward any packets from H3 to GW3, thereby "tricking" H3 into using GW2 as its default router?

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• IP route ppp0 + eth0 access to outside network

  - by Vitor

  I need some help in define a route I have two connections one from eth0 and other a ppp0 (a 3G card) Not having the ppp0 connection active my route table is: Destination Gateway Genmask Flags Metric Ref Use Iface default DD-WRT 0.0.0.0 UG 100 0 0 eth0 192.168.1.0 * 255.255.255.0 U 0 0 0 eth0 I can access my webserver from an outside network through ethernet interface Than I have also my ppp0 3G connection active havig the following route table: D estination Gateway Genmask Flags Metric Ref Use Iface default 10.64.64.64 0.0.0.0 UG 0 0 0 ppp0 10.64.64.64 * 255.255.255.255 UH 0 0 0 ppp0 192.168.1.0 * 255.255.255.0 U 0 0 0 eth0 Now I only can access my webserver in outside networks through the IP of the 3G connection Note that my server is serving at 0.0.0.0 IP (to all interfaces) But I need to get access to webserver to both interfaces ethernet and 3G connection I only can have access to both connection in local network Any help to configure this network to have both interfaces with outside networks access is welcome Can anyone give me an example to configure this network with 2 gateways to give outside networks access One for IP 192.168.1.149 and other for the ppp0 IP 89.214.60.196 Tanks

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• How to resolve IPs in DNS based on the subnet of the requesting client?

  - by Nohsib

  Is it possible to configure Bind9 or other DNS to resolve the domain name of a machine into different IPs based on the subnet of the requesting client? e.g. Say the same service is running on 2 different application servers at different geographical points and based on the incoming request to resolve the domain name, the name server provides the IP of the application server based on the requesting client's IP, so the service could be offered by servers that are geographically closer to the client. In short, something like a CDN but just the IP resolution part based on the client's subnet. Is this configurable in any DNS?

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• Wicd not playing well with networks that utilize network access control

  - by Sion

  Starting a couple months ago (might be able to find exact date if necessary) my installation of Wicd stopped being able to see wireless networks that use NAC (Network Access Control) such as Aruba networks. But if I shut down Wicd and start NetworkManager I can connect to said networks and log in to them depending on what the NAC requires. This is the current wicd package installed: net-misc/wicd-1.7.1_pre20111210-r1 This is how I manipulate the network manager running: su -c'/etc/init.d/wicd stop; /etc/init.d/NetworkManager start' What would cause this specific of a problem to occur?

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• /proc/net/dev and /sys/class/net/ bogus network interface names

  - by sfink

  I am constructing a list of network interfaces to monitor based on the contents of /proc/net/dev. But I am getting some bogus interfaces in the list: __tmp1104705027 __tmp974528607 Where do those come from? They also show up in /sys/class/net/: # ls -1 /sys/class/net/ eth0 eth1 eth2 eth3 lo sit0 __tmp1104705027 __tmp974528607 For now, I think I'll just ignore anything starting with __tmp, but I'd like to know what they are and where they come from. This is on a recompiled CentOS 5.3 kernel: 2.6.18-128.7.1.el5.tvh.7PAE #1 SMP PREEMPT

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• Assign fixed IP address via DHCP by DNS lookup

  - by Janoszen

  Preface I'm building a virtualization environment with Ubuntu 14.04 and LXC. I don't want to write my own template since the upgrade from 12.04 to 14.04 has shown that backwards compatibility is not guaranteed. Therefore I'm deploying my virtual machines via lxc-create, using the default Ubuntu template. The DNS for the servers is provided by Amazon Route 53, so no local DNS server is needed. I also use Puppet to configure my servers, so I want to keep the manual effort on the deployment minimal. Now, the default Ubuntu template assigns IP addresses via DHCP. Therefore, I need a local DHCP server to assign IP addresses to the nodes, so I can SSH into them and get Puppet running. Since Puppet requires a proper DNS setup, assigning temporary IP addresses is not an option, the client needs to get the right hostname and IP address from the start. Question What DHCP server do I use and how do I get it to assign the IP address based only on the host-name DHCP option by performing a DNS lookup on that very host name? What I've tried I tried to make it work using the ISC DHCP server, however, the manual clearly states: Please be aware that only the dhcp-client-identifier option and the hardware address can be used to match a host declaration, or the host-identifier option parameter for DHCPv6 servers. For example, it is not possible to match a host declaration to a host-name option. This is because the host-name option cannot be guaranteed to be unique for any given client, whereas both the hardware address and dhcp-client-identifier option are at least theoretically guaranteed to be unique to a given client. I also tried to create a class that matches the hostname like this: class "my-client-name" { match if option host-name = "my-client-name"; fixed-address my-client-name.my-domain.com; } Unfortunately the fixed-address option is not allowed in class statements. I can replace it with a 1-size pool, which works as expected: subnet 10.103.0.0 netmask 255.255.0.0 { option routers 10.103.1.1; class "my-client-name" { match if option host-name = "my-client-name"; } pool { allow members of "my-client-name"; range 10.103.1.2 10.103.1.2; } } However, this would require me to administer the IP addresses in two places (Amazon Route53 and the DHCP server), which I would prefer not to do. About security Since this is only used in the bootstrapping phase on an internal network and is then replaced by a static network configuration by Puppet, this shouldn't be an issue from a security standpoint. I am, however, aware that the virtual machine bootstraps with "ubuntu:ubuntu" credentials, which I intend to fix once this is running.

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• Why do Ping and Dig provide different IP address than nslookup?

  - by user1032531

  When pinging my domain name which points to my home public IP from two different servers on my LAN, it shows them pinging different IP. Further investigation shows dig and nslookup providing different results. See below. A little history. My IP used to be 11.22.33.444 and is hosted by Comcast. I changed routers, and it somehow got changed to 55.66.77.888. I've since updated my 1and1 domain name to point to the 55.66.77.888. desktop is a basic server, runs the web server, and connects wirelessly to my LAN. laptop is a GUI and connected via CAT5. Both operate Centos6.4. My old router was a D-Link, and used their "Virtual Server" feature to pass port 80 to desktop. My new router is a Linksys, and I use their "Port Forwarding" feature to pass port 80 to desktop (however, I haven't gotten this part working yet). What is going on??? Why the different IPs? Obviously, it most somehow be stored on the server, but why does the actual machine even know the public IP since it is on a LAN? How do I purge the old IP? [root@desktop etc]# dig +short myDomain.com 11.22.33.444 [root@desktop etc]# nslookup www.myDomain.com Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: www.myDomain.com Address: 55.66.77.888 [root@desktop etc]# dig myDomain.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6_4.6 <<>> myDomain.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13822 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;myDomain.com. IN A ;; ANSWER SECTION: myDomain.com. 16031 IN A 11.22.33.444 ;; Query time: 21 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Mon Oct 21 04:36:52 2013 ;; MSG SIZE rcvd: 44 [root@desktop etc]# [root@laptop ~]# dig +short myDomain.com 55.66.77.888 [root@laptop ~]# nslookup www.myDomain.com Server: 192.168.0.1 Address: 192.168.0.1#53 Non-authoritative answer: Name: www.myDomain.com Address: 55.66.77.888 [root@laptop ~]#

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• Improving TCP performance over a gigabit network with lots of connections and high traffic of small packets

  - by MinimeDJ

  I’m trying to improve my TCP throughput over a “gigabit network with lots of connections and high traffic of small packets”. My server OS is Ubuntu 11.10 Server 64bit. There are about 50.000 (and growing) clients connected to my server through TCP Sockets (all on the same port). 95% of of my packets have size of 1-150 bytes (TCP header and payload). The rest 5% vary from 150 up to 4096+ bytes. With the config below my server can handle traffic up to 30 Mbps (full duplex). Can you please advice best practice to tune OS for my needs? My /etc/sysctl.cong looks like this: kernel.pid_max = 1000000 net.ipv4.ip_local_port_range = 2500 65000 fs.file-max = 1000000 # net.core.netdev_max_backlog=3000 net.ipv4.tcp_sack=0 # net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.core.somaxconn = 2048 # net.ipv4.tcp_rmem = 4096 87380 16777216 net.ipv4.tcp_wmem = 4096 65536 16777216 # net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_mem = 50576 64768 98152 # net.core.wmem_default = 65536 net.core.rmem_default = 65536 net.ipv4.tcp_window_scaling=1 # net.ipv4.tcp_mem= 98304 131072 196608 # net.ipv4.tcp_timestamps = 0 net.ipv4.tcp_rfc1337 = 1 net.ipv4.ip_forward = 0 net.ipv4.tcp_congestion_control=cubic net.ipv4.tcp_tw_recycle = 0 net.ipv4.tcp_tw_reuse = 0 # net.ipv4.tcp_orphan_retries = 1 net.ipv4.tcp_fin_timeout = 25 net.ipv4.tcp_max_orphans = 8192 Here are my limits: $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 193045 max locked memory (kbytes, -l) 64 max memory size (kbytes, -m) unlimited open files (-n) 1000000 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 8192 cpu time (seconds, -t) unlimited max user processes (-u) 1000000 [ADDED] My NICs are the following: $ dmesg | grep Broad [ 2.473081] Broadcom NetXtreme II 5771x 10Gigabit Ethernet Driver bnx2x 1.62.12-0 (2011/03/20) [ 2.477808] bnx2x 0000:02:00.0: eth0: Broadcom NetXtreme II BCM57711E XGb (A0) PCI-E x4 5GHz (Gen2) found at mem fb000000, IRQ 28, node addr d8:d3:85:bd:23:08 [ 2.482556] bnx2x 0000:02:00.1: eth1: Broadcom NetXtreme II BCM57711E XGb (A0) PCI-E x4 5GHz (Gen2) found at mem fa000000, IRQ 40, node addr d8:d3:85:bd:23:0c [ADDED 2] ethtool -k eth0 Offload parameters for eth0: rx-checksumming: on tx-checksumming: on scatter-gather: on tcp-segmentation-offload: on udp-fragmentation-offload: off generic-segmentation-offload: on generic-receive-offload: on large-receive-offload: on rx-vlan-offload: on tx-vlan-offload: on ntuple-filters: off receive-hashing: off [ADDED 3] sudo ethtool -S eth0|grep -vw 0 NIC statistics: [1]: rx_bytes: 17521104292 [1]: rx_ucast_packets: 118326392 [1]: tx_bytes: 35351475694 [1]: tx_ucast_packets: 191723897 [2]: rx_bytes: 16569945203 [2]: rx_ucast_packets: 114055437 [2]: tx_bytes: 36748975961 [2]: tx_ucast_packets: 194800859 [3]: rx_bytes: 16222309010 [3]: rx_ucast_packets: 109397802 [3]: tx_bytes: 36034786682 [3]: tx_ucast_packets: 198238209 [4]: rx_bytes: 14884911384 [4]: rx_ucast_packets: 104081414 [4]: rx_discards: 5828 [4]: rx_csum_offload_errors: 1 [4]: tx_bytes: 35663361789 [4]: tx_ucast_packets: 194024824 [5]: rx_bytes: 16465075461 [5]: rx_ucast_packets: 110637200 [5]: tx_bytes: 43720432434 [5]: tx_ucast_packets: 202041894 [6]: rx_bytes: 16788706505 [6]: rx_ucast_packets: 113123182 [6]: tx_bytes: 38443961940 [6]: tx_ucast_packets: 202415075 [7]: rx_bytes: 16287423304 [7]: rx_ucast_packets: 110369475 [7]: rx_csum_offload_errors: 1 [7]: tx_bytes: 35104168638 [7]: tx_ucast_packets: 184905201 [8]: rx_bytes: 12689721791 [8]: rx_ucast_packets: 87616037 [8]: rx_discards: 2638 [8]: tx_bytes: 36133395431 [8]: tx_ucast_packets: 196547264 [9]: rx_bytes: 15007548011 [9]: rx_ucast_packets: 98183525 [9]: rx_csum_offload_errors: 1 [9]: tx_bytes: 34871314517 [9]: tx_ucast_packets: 188532637 [9]: tx_mcast_packets: 12 [10]: rx_bytes: 12112044826 [10]: rx_ucast_packets: 84335465 [10]: rx_discards: 2494 [10]: tx_bytes: 36562151913 [10]: tx_ucast_packets: 195658548 [11]: rx_bytes: 12873153712 [11]: rx_ucast_packets: 89305791 [11]: rx_discards: 2990 [11]: tx_bytes: 36348541675 [11]: tx_ucast_packets: 194155226 [12]: rx_bytes: 12768100958 [12]: rx_ucast_packets: 89350917 [12]: rx_discards: 2667 [12]: tx_bytes: 35730240389 [12]: tx_ucast_packets: 192254480 [13]: rx_bytes: 14533227468 [13]: rx_ucast_packets: 98139795 [13]: tx_bytes: 35954232494 [13]: tx_ucast_packets: 194573612 [13]: tx_bcast_packets: 2 [14]: rx_bytes: 13258647069 [14]: rx_ucast_packets: 92856762 [14]: rx_discards: 3509 [14]: rx_csum_offload_errors: 1 [14]: tx_bytes: 35663586641 [14]: tx_ucast_packets: 189661305 rx_bytes: 226125043936 rx_ucast_packets: 1536428109 rx_bcast_packets: 351 rx_discards: 20126 rx_filtered_packets: 8694 rx_csum_offload_errors: 11 tx_bytes: 548442367057 tx_ucast_packets: 2915571846 tx_mcast_packets: 12 tx_bcast_packets: 2 tx_64_byte_packets: 35417154 tx_65_to_127_byte_packets: 2006984660 tx_128_to_255_byte_packets: 373733514 tx_256_to_511_byte_packets: 378121090 tx_512_to_1023_byte_packets: 77643490 tx_1024_to_1522_byte_packets: 43669214 tx_pause_frames: 228 Some info about SACK: When to turn TCP SACK off?

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• Wake On Lan for Fedora 12

  - by Toymakerii

  I have a fedora 12 box that I am using as a sandbox for web development and a few other toys. The box gets really hot so I would like it to sleep/hibernate when no one is using it, however most of the people connecting to the box will not be able to access it physically. Is it possible to set up a Wake On Lan that wakes up the machine when it detects an SSH connection? A google search didn't yield much information. (or atleast I wasn't smart enough to register it as useful!)

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• Debian 7: "Failure of key exchange and association"

  - by pyrogoggles

  I'm installing Debian using the Live CD with GNOME and the non-free packages. The internet works just fine when using the live CD, but when you try to open the installer and select a network, it gives me the error of "Failure of key exchange and association". I've put everything in right, and tried multiple times. However, it never works. Am I just going to have to use ethernet to install? Thanks, people.

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• Rate limit a wireless interface

  - by Jamie Hankins

  I have access to my routers SSH and IPTables. I want to rate limit my guest network to 1Mb/s so they can't guzzle my bandwidth. rai1 RTWIFI SoftAP ESSID:"GuestNetwork" Nickname:"" Mode:Managed Channel=6 Access Point: :F9 Bit Rate=300 Mb/s wdsi0 RTWIFI SoftAP ESSID:"YouCan'tTouchThis" Nickname:"" Mode:Managed Channel=6 Access Point: :F8 Bit Rate=300 Mb/s wdsi1 RTWIFI SoftAP ESSID:"YouCan'tTouchThis" Nickname:"" Mode:Managed Channel=6 Access Point: :F9 Bit Rate=300 Mb/s wdsi2 RTWIFI SoftAP ESSID:"YouCan'tTouchThis" Nickname:"" Mode:Managed Channel=6 Access Point: Not-Associated Bit Rate:300 Mb/s wdsi3 RTWIFI SoftAP ESSID:"YouCan'tTouchThis" Nickname:"" Mode:Managed Channel=6 Access Point: Not-Associated Bit Rate:300 Mb/s I'm just wondering the command I need to limit it. I tried the iwconfig limit command but it failed. Thanks

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• How to prevent Ubuntu from combining networks on 2 NIC server?

  - by SolarPower

  I've got a Ubuntu Server 10.10 with 2 network interfaces with a cable plugged into both going to switches on completely different networks with different routers. One network is the 10.1.10.X network with a separate gateway/router - the server has an IP of 10.1.10.50 with the gateway IP of 10.1.10.1. The other interface is 10.2.10.X, IP 10.2.10.50, gateway 10.2.10.1. All my Mac machines are on the 10.2.10.X network, and all servers on the 10.1.10.X. The ONLY connection between the two is this machine. From a Mac in my office, I CANNOT ping any computer on the 10.1.10.X network except the Ubuntu machine I'm talking about. However, under the Shared column in Finder, I can see every server on the other network listed. That makes me believe that somehow this Ubuntu machine is letting certain requests span both networks, which is a security problem. Hope this is enough info.

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• 2 nics. 2 Defaults Gateways

  - by andre.dias

  Here is my scenario: i have this server with 2 nics, each one with different IPs, connected to differents routers. Almost everything is configured whe way i need. Traffic coming from eth0 exits using eth0, traffic coming from eth1 exits using eth1. And there is a default gateway configured. $route: default IP 0.0.0.0 UG 0 0 0 eth0 With this configuration, the traffic generated in the server is going out using eth0 (lynx www.google.com for example). The problem is: the Internet link from eth0 went down today. The traffic coming from eth1 was ok...no problem. But the traffic generated in the server was a problem...the default gateway was out...no access do the Internet anymore (no more lynx www.google.com) So i added a new default gateway configuration, pointing to eth1. For 30 minutes i kept that way...2 default gateways, but just one was "working"...and everything was working just fine. But then i removed de eth0 gateway entry because, well, 2 default gateways is kind of weird. My question: is there any problem on keeping these 2 default gateways, one for each? So i don´t need to do nothing when one link go down again? $route: default IP1 0.0.0.0 UG 0 0 0 eth0 default IP2 0.0.0.0 UG 0 0 0 eth1

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• correct routing for multiple devices

  - by helmi

  I have Debian Lenny machine with 3 interfaces enabled (eth0-2), and I have problems as follow. eth1 is connected to a router and this router has portforwarding for port80. eth2 is connected direct to the internet If I open a website hosted on my system via the router it works fine. If I try to open the same via the eth2 connetion it does not! tshark shows incomming trafic on eth2 but nothing goes out there. iptabes accepts all My routing table: Ziel Router Genmask Flags Metric Ref Use Iface 10.9.0.2 * 255.255.255.255 UH 0 0 0 tun0 212.236.24.128 * 255.255.255.224 U 0 0 0 eth2 192.168.1.0 * 255.255.255.0 U 0 0 0 eth1 192.168.0.0 * 255.255.255.0 U 0 0 0 eth0 10.9.0.0 10.9.0.2 255.255.255.0 UG 0 0 0 tun0 default 192.168.1.1 0.0.0.0 UG 0 0 0 eth1 default 212.236.024.129 0.0.0.0 UG 0 0 0 eth2 default 192.168.0.1 0.0.0.0 UG 0 0 0 eth0

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• What do "Unknown SSAP" and "Unknown DSAP" mean in tcpdump?

  - by lacker

  While trying to fix a problem with intermittently losing internet connection on a machine with a wireless connection to a router, I ran tcpdump and noticed packets with "Unknown SSAP" and "Unknown DSAP" errors coming at a rate of a few per second. 20:27:21.703178 00:24:a5:af:24:f6 (oui Unknown) Unknown SSAP 0xde > 1c:65:9d:48:38:95 (oui Unknown) Unknown DSAP 0xe2 Information, send seq 0, rcv seq 16, Flags [Response], length 171 20:27:21.724726 00:24:a5:af:24:f6 (oui Unknown) Unknown SSAP 0xde > 1c:65:9d:48:38:95 (oui Unknown) Unknown DSAP 0xe2 Information, send seq 0, rcv seq 16, Flags [Response], length 104 20:27:21.746449 00:24:a5:af:24:f6 (oui Unknown) Unknown SSAP 0xde > 1c:65:9d:48:38:95 (oui Unknown) Unknown DSAP 0xe4 Information, send seq 0, rcv seq 16, Flags [Response], length 88 20:27:21.970963 00:24:a5:af:24:f6 (oui Unknown) Unknown SSAP 0xde > 1c:65:9d:48:38:95 (oui Unknown) Unknown DSAP 0xe8 Information, send seq 0, rcv seq 16, Flags [Response], length 76 20:27:22.016565 00:24:a5:af:24:f6 (oui Unknown) Unknown SSAP 0xde > 1c:65:9d:48:38:95 (oui Unknown) Unknown DSAP 0xea Information, send seq 0, rcv seq 16, Flags [Response], length 88 20:27:22.038471 00:24:a5:af:24:f6 (oui Unknown) Unknown SSAP 0xde > 1c:65:9d:48:38:95 (oui Unknown) Unknown DSAP 0xea Information, send seq 0, rcv seq 16, Flags [Response], length 171 What does the "Unknown SSAP" and "Unknown DSAP" mean, and does it indicate a problem?

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• IPv6 static routes

  - by user98651

  I am looking to configure a few hosts with IPv6 on my network. The router (running CentOS 5) is configured with an Hurricane Electric (HE) tunnel which works fine on that host. However, I would like to statically add a few additional hosts on the same LAN to have IPv6 through this tunnel. No, I don't want radvd or dhcpv6 to do the work for me in this case. I already have IPv6 forwarding enabled in sysctl.conf. I am looking for help with the next steps (statically adding the routes). Lets say the IP addresses are as follows: Router: 2001:470:1b07:1:: Host1: 2001:470:1b07:2:: How would I go about making them see each other? Thanks in advance for the help.

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