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  • Finding cause of TCP retransmission within a LAN

    - by Surreal
    Hello denizens of Server Fault I have an irritating problem with a LAN of about 100 computers, 2 Windows domain servers, and 12 VoIP phones. Since their installation around a year ago, every week or so, we notice a VoIP phone resetting itself - occasionally in the middle of a call. Simultaneously there are often signs of temporary loss of connection on computers: freezes in explorer while accessing network shares, errors in our administration software due to loss of connection to the database server. I have been doing some Wireshark monitoring on the connection between the VoIP PBX and the rest of the network. Wireshark picks up a clump of retransmitted TCP packets at the times when we record phone restarts. The Wireshark log shows about 2 clusters of retransmissions a day ranging from 5 packets to hundreds. Those in each cluster are mainly between the PBX and some set of the VoIP phones, but not always the same set. Often retransmissions at the same time are to phones connected to the same switch, but sometimes retransmissions occur together to phones at opposite ends of the network. There are usually some coincident retransmissions in passing TCP traffic, for example between client machines and the file servers. The spikes in retransmissions and phone resets do not correlate well with when the network is heavily loaded. They seem to occur slightly more during the day, but most in the evening, when traffic should be decreasing. They occur reasonably often late at night when most computers are turned off and traffic should be lowest. Do you have any ideas that might help diagnose the cause of problems like this? One thing I have not yet tried, but should have, is updating the firmware of all the switches.

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  • Apache Reverse proxy for intranet and other integrated application on intranet

    - by user1433448
    I'm trying to configure a reverse proxy (ssl) with apache 2.2 in Debian Squeeze, but I have some problems, specially with some path absolute and with https I'll try to detail what I have made and what I'm trying to configure I have a server Debian Squeeze with apache2.2 + mod_proxy_html with: # apt-get install libapache2-mod-proxy-html libxml2-dev # a2enmod proxy # a2enmod proxy_http # a2enmod proxy_html # a2enmod headers After that I have configured a virtual host with: reverse_proxy_ssl.conf I'm trying to configure to allow access of our intranet from internet with a reverse proxy (apache that is located in DMZ). With this configuration domain.com/intranet works correctly and we can access to intranet, but we have one problem when from domain.com/intranet we need to use another internal application that is called from intranet with absolute path ( https://192.168.10.25/application/) and from internet appears that try to access with internal ip, and this link es incorrect from external site We only need to access from intranet to multiple internal application that are in external server and we like to restrict to minimal access from internet. All the application that are in the smae server of intranet are working. The second problem is with https and reverse proxy in our firewall appears some errors with packets (not valid packets), and with https seems to work. What can I do to solve this problems (absolute path and ssl problem) Thanks

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  • NETKEY IPsec and ARP

    - by Shawn J. Goff
    I'm wondering if I have the correct routing setup for an IPsec tunnel. I have control over the IPsec endpoints and the hosts connected to one side. These hosts are connecting to the tunnel so that they have access to the network on the other side of what I will call the IPsec server. I don't have control of the network upstream of this server. Normally, the IPsec server will not respond to ARP requests for the hosts on the other side of the tunnel. So when a packet arrives for one of my hosts the server gets ARP requests, but the upstream router gets no response, and cannot construct the ethernet frame to send me the packets. If I was using one of the swan stacks, I would have a separate interface, and I'd probably just need to turn on proxyarp, but I'm using NETKEY, which doesn't use a separate interface for the tunnel. To solve the problem for now, I have added an eth0.5 vlan to the IPsec server, turned on proxyarp for that interface, and added all routes my hosts addresses to that interface so that it will respond to those ARP requests (and will therefore get relevant packets routed to it). This works, but it feels wrong. What is the correct way to get the upstream router to send me the traffic for these hosts?

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  • FreeBSD slow transfers - RFC 1323 scaling issue?

    - by Trey
    I think I may be having an issue with window scaling (RFC 1323) and am hoping that someone can enlighten me on what's going on. Server: FreeBSD 9, apache22, serving a static 100MB zip file. 192.168.18.30 Client: Mac OS X 10.6, Firefox 192.168.17.47 Network: Only a switch between them - the subnet is 192.168.16/22 (In this test, I also have dummynet filtering simulating an 80ms ping time on all IP traffic. I've seen nearly identical traces with a "real" setup, with real internet traffic/latency also) Questions: Does this look normal? Is packet #2 specifying a window size of 65535 and a scale of 512? Is packet #5 then shrinking the window size so it can use the 512 scale and still keep the overall calculated window size near 64K? Why is the window scale so high? Here are the first 6 packets from wireshark. For packets 5 and 6 I've included the details showing the window size and scaling factor being used for the data transfer. Code: No. Time Source Destination Protocol Length Info 108 6.699922 192.168.17.47 192.168.18.30 TCP 78 49190 http [SYN] Seq=0 Win=65535 Len=0 MSS=1460 WS=8 TSval=945617489 TSecr=0 SACK_PERM=1 115 6.781971 192.168.18.30 192.168.17.47 TCP 74 http 49190 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 WS=512 SACK_PERM=1 TSval=2617517338 TSecr=945617489 116 6.782218 192.168.17.47 192.168.18.30 TCP 66 49190 http [ACK] Seq=1 Ack=1 Win=524280 Len=0 TSval=945617490 TSecr=2617517338 117 6.782220 192.168.17.47 192.168.18.30 HTTP 490 GET /utils/speedtest/large.file.zip HTTP/1.1 118 6.867070 192.168.18.30 192.168.17.47 TCP 375 [TCP segment of a reassembled PDU] Details: Transmission Control Protocol, Src Port: http (80), Dst Port: 49190 (49190), Seq: 1, Ack: 425, Len: 309 Source port: http (80) Destination port: 49190 (49190) [Stream index: 4] Sequence number: 1 (relative sequence number) [Next sequence number: 310 (relative sequence number)] Acknowledgement number: 425 (relative ack number) Header length: 32 bytes Flags: 0x018 (PSH, ACK) Window size value: 130 [Calculated window size: 66560] [Window size scaling factor: 512] Checksum: 0xd182 [validation disabled] Options: (12 bytes) No-Operation (NOP) No-Operation (NOP) Timestamps: TSval 2617517423, TSecr 945617490 [SEQ/ACK analysis] TCP segment data (309 bytes) Note: originally posted http://forums.freebsd.org/showthread.php?t=32552

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  • NFS high CPU usage

    - by user269836
    Hello, I have a very strange issue. I have next server: Intel(R) Xeon(TM) MP CPU 3.16GHz cat /proc/cpuinfo | grep proce | wc -l 8 free -m total used free shared buffers cached Mem: 28203 27606 596 0 10789 9714 -/+ buffers/cache: 7103 21100 Swap: 24695 0 24695 RAID card *-storage description: RAID bus controller product: MegaRAID vendor: LSI Logic / Symbios Logic physical id: 7 bus info: pci@0000:13:07.0 logical name: scsi2 version: 01 width: 32 bits clock: 66MHz capabilities: storage pm bus_master cap_list rom configuration: driver=megaraid latency=32 resources: irq:134 memory:d8ff0000-d8ffffff(prefetchable) memory:df600000-df60ffff(prefetchable) HDD: 10x148Gb SCSI U320 15k - RAID5 /dev/sdb1 807G 674G 93G 88% /storage /dev/sdb1 /storage ext4 defaults,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv0,noatime,nodiratime,noacl,errors=remount-ro 0 1 network cards ethtool -i eth0 driver: tg3 version: 3.116 firmware-version: 5704-v3.36, ASFIPMIc v2.36 bus-info: 0000:10:02.0 ethtool -i eth1 driver: tg3 version: 3.116 firmware-version: 5704-v3.36, ASFIPMIc v2.36 bus-info: 0000:10:02.0 ifconfig bond0 Link encap:Ethernet HWaddr 00:0f:1f:ff:d6:4d inet addr:192.168.15.71 Bcast:192.168.15.255 Mask:255.255.255.0 inet6 addr: fe80::20f:1fff:feff:d64d/64 Scope:Link UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1 RX packets:1062818202 errors:0 dropped:3918 overruns:0 frame:0 TX packets:1041317321 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10000 RX bytes:258867684559 (241.0 GiB) TX bytes:396569192650 (369.3 GiB) this server running only nfs-kernel-server uname -a Linux nas2-backup 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux Debian 6. What do I have, once per day or two, LA goes up, it can be reached around LA: 40 but if I do: nfs-kernel-server restart. Every thing is OK. But on the next day or a little bit later, LA goes up again. Servers are connected to d-link dgs 1016d with 24 GBits ports. I have tried everything to find out what the problem is. Why it's happening, but still I can not resolve this issue. Any ideas on what is happening here?

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  • Cisco QoS Guidance

    - by Kyle Brandt
    I have a 10M connection to the internet that is hooked into a 100M port. I am getting started with QoS, and am hopping for a little guidance on setting it up on a Cisco 3825 router. Right now I am going forward with the idea that I have to implement it on my router, and the provider can't provide QoS for me. How I envision it working is that the QoS will drop or queue packets on my router and that will help prevent a situation where the provider has to start dropping a lot of packets. Right now all I am tasked with is making sure that one of the 3 LANs gets a certain slice (say 3M for Gig Lan1) of the 10M internet connection (But ideally this will be more flexible in the Future). 10M Internet on 100M port on HWIC-4ESW +-----------------------+ | | Gig Lan1 | Cisco 3825 | Lan3 on HWIC-4ESW | | +-----------------------+ Gig Lan2 I need to learn more about QoS, but having a target technology and maybe example configuration will help me wrap my head around the reading I am doing a little more. Which Cisco QoS Technology do you recommend for this particular situation? Have a basic sample config of how this might work? Right now the 10M line is not congested, so this more to have something in place in case it starts to become mildly congested in the future. I do have VOIP at one location connected to this one over the Internet that goes through a VPN tunnel. Everything else that is between this location and other offices is on a separate MPLS network.

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  • NTOP gives warnings on startup

    - by FR6
    I just installed ntop 1.4.4 and when I start it, it give me infinite warnings "packet truncated": ... RRD_DEBUG: umask 0066 RRD_DEBUG: DirPerms 0700 THREADMGMT: RRD: Started thread (t2992630672) for data collection THREADMGMT[t2992630672]: RRD: Data collection thread starting [p30923] INIT: Created pid file (/var/run/ntop.pid) THREADMGMT[t3086329552]: ntop RUNSTATE: INITNONROOT(3) Now running as requested user 'nobody' (99:99) Note: Reporting device initally set to 0 [eth0] (merged) THREADMGMT[t3086329552]: ntop RUNSTATE: RUN(4) THREADMGMT[t2982140816]: NPS(1): Started thread for network packet sniffing [eth0] THREADMGMT[t2982140816]: NPS(eth0): pcapDispatch thread starting [p30923] THREADMGMT[t2982140816]: NPS(eth0): pcapDispatch thread running [p30923] THREADMGMT[t3047009168]: SIH: Idle host scan thread running [p30923] THREADMGMT[t3057499024]: SFP: Fingerprint scan thread running [p30923] **WARNING** packet truncated (8814->8232) **WARNING** packet truncated (10274->8232) **WARNING** packet truncated (8814->8232) **WARNING** packet truncated (8814->8232) ... Do I need to configure something? I tried to access the web interface (http://localhost:3000) but it does not work. Note: I'm on CentOS. EDIT: Not sure if it helps but there is my "ifconfig": eth0 Link encap:Ethernet HWaddr 00:16:76:BC:7E:77 inet addr:192.168.0.221 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::216:76ff:febc:7e77/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:15496640 errors:0 dropped:0 overruns:0 frame:0 TX packets:19256813 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:836230629 (797.4 MiB) TX bytes:608496148 (580.3 MiB) Memory:dffe0000-e0000000

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  • virtualisation with kvm: export services from guest to the host

    - by ascobol
    Hello, I would like to export some services from the guest os to the host os, via kvm, and by the same way learn some things about networking. I have tried the following commands: In the host (kubuntu 10.4): $ sudo tunctl -u ascobol Set 'tap0' persistent and owned by uid 2401 $ sudo ifconfig tap0 192.168.2.1 netmask 255.255.255.0 broadcast 192.168.2.255 The ifconfig command returns: $ /sbin/ifconfig tap0 Link encap:Ethernet HWaddr 3e:4e:e3:cc:bc:92 inet addr:192.168.2.1 Bcast:192.168.2.255 Mask:255.255.255.0 inet6 addr: fe80::3c4e:e3ff:fecc:bc92/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:17 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) $ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 tap0 Then I run the virtual machine (ubuntu server 10.4): $ sudo kvm -hda ubuntuserver104.qcow2 -net nic -net tap,name=tap0,script=no (I'm using sudo because without it fails with the following message:) warning: could not configure /dev/net/tun: no virtual network emulation With sudo the virtual machine boots, I just get this message: pci_add_option_rom: failed to find romfile "pxe-rtl8139.bin" In the virtual machine: $ ifconfig eth0 192.168.2.2 netmask 255.255.255.0 broadcast 192.168.2.255 Now if I run: $ ssh 192.168.2.2 I just get a No route to host What is wrong with this setup ? Thanks !

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  • Iptables: "-p udp --state ESTABLISHED"

    - by chris_l
    Hi, let's look at these two iptables rules which are often used to allow outgoing DNS: iptables -A OUTPUT -p udp --sport 1024:65535 --dport 53 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p udp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT My question is: How exactly should I understand the ESTABLISHED state in UDP? UDP is stateless. Here is my intuition - I'd like to know, if or where this is incorrect: The man page tells me this: state This module, when combined with connection tracking, allows access to the connection tracking state for this packet. --state ... So, iptables basically remembers the port number that was used for the outgoing packet (what else could it remember for a UDP packet?), and then allows the first incoming packet that is sent back within a short timeframe? An attacker would have to guess the port number (would that really be too hard?) About avoiding conflicts: The kernel keeps track of which ports are blocked (either by other services, or by previous outgoing UDP packets), so that these ports will not be used for new outgoing DNS packets within the timeframe? (What would happen, if I accidentally tried to start a service on that port within the timeframe - would that attempt be denied/blocked?) Please find all errors in the above text :-) Thanks, Chris

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  • pptpd-logwtmp.so config wrong ip address

    - by rgc
    i have setup a pptp vpn on ubuntu 10.04, and i config local ip address , remote ip address as following: local IP address 10.0.30.100 remote IP address 192.168.13.100 after i use windows to connect to vpn server in windows , i only could send packets, can not receive any packets. i also check the pptp log in ubuntu server, and find this strange thing rcvd [IPCP ConfAck id=0x1 <compress VJ 0f 01> <addr 10.0.30.100>] rcvd [IPCP ConfReq id=0x2 <compress VJ 0f 01> <addr 192.168.13.100> <ms-dns1 202.119.32.6> <ms-dns2 202.119.32.12>] sent [IPCP ConfAck id=0x2 <compress VJ 0f 01> <addr 192.168.13.100> <ms-dns1 202.119.32.6> <ms-dns2 202.119.32.12>] Cannot determine ethernet address for proxy ARP local IP address 10.0.30.100 remote IP address 192.168.13.100 pptpd-logwtmp.so ip-up ppp0 **172.25.146.174** i did not set 172.25.146.174, it should be 192.168.13.100, can anyone tell me what should i do to fix this problem?

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  • Add IPv6 support to DirectAdmin server

    - by George Boot
    I just set up an new DirectAdmin, and I want to prepare it for IPv6 use. My ISP have gave me an range of IPv6 addresses that I can use. Lets say that address is 2a01:7c8:**:1f::. My neworkadapter user DHCP to resolves its IP-addresses. When i type ifoncig eth0 I get the following result: eth0 Link encap:Ethernet HWaddr 52:**:**:**:ce:f3 inet addr:37.**.**.44 Bcast:37.**.**.255 Mask:255.255.255.0 inet6 addr: 2a01:7c8:****:1f::/64 Scope:Global inet6 addr: fe80::5054:ff:fe87:cef3/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:38941 errors:0 dropped:0 overruns:0 frame:0 TX packets:29439 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3779534 (3.6 MiB) TX bytes:5089379 (4.8 MiB) As you can see, I have an IPv6 address set, but I can't ping6 an IPv6 host. I get the error: connect: Network is unreachable. I decided that I needed an gateway, so I tryed to add one: ip -6 route add default via 2a01:7c8:****::1 dev eth0 (2a01:7c8:**::1 is the gateway of my ISP). But it trows an error: RTNETLINK answers: No route to host. Does somebody know what to do, and how to solve this issue? Thanks a lot!

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  • Using Round Robin DNS on simple VPN setup

    - by dannymcc
    We have two internet connections which are load balanced to share the load between the two. We set this up after one of the internet provider proved to be less than reliable but great speed and latency wise when it is working. We'd rather utilise both connections as much as possible rather than leave one idle until the other drops out. We have a number of remote workers who occasionally need to connect via VPN from their laptops or iPads, we also have a small number of permanent LAN to LAN tunnels running from smaller branches. Originally we only had one internet connection and used one of our static IP addresses for all VPN users. Now that we have two internet connections running all of the time I am trying to make sure that the VPN is available to our team regardless of which connection drops. So my solution is to create two A records for our domain name with a value of vpn. and the two static IP addresses from each peer. Is this a sensible way of achieving this? Should I expect higher latency due to packets being lost if one peer fails and some packets still get routed to it anyway? A brief mockup of the setup I have:

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  • Is it possible to trace the delegation path for a DNS lookup?

    - by Josh Glover
    I'm trying to determine why a Nagios host check is failing (hostnames and IPs have been changed to protect the guilty): : jmglov@laurana; host www.foo.com ;; connection timed out; no servers could be reached : jmglov@laurana; for ns in `grep -o '\([0-9]\+[.]\)\{3\}[0-9]\+$' /etc/resolv.conf`; do ping -qc 1 $ns; done PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data. --- 192.168.1.1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 10.911/10.911/10.911/0.000 ms PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data. --- 192.168.1.2 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.241/0.241/0.241/0.000 ms So I know that my nameservers are reachable, meaning that some nameserver along the delegation path to the authoritative nameserver for my host is not responding. Is there an easy way to determine which nameserver this is (basically a traceroute for DNS)?

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  • Xen PV packet loss

    - by Delphinator
    I'm having some serious issues with packetloss with one of my servers. This server is a somewhat old (P4-era) machine running Debian Squeeze and Xen 4.0. There are two domUs running on it (both also Debian Squeeze), one gateway and a fileserver. Unfortunatly the processor has no virtualization extensions, therefore only PV can be used. While investigating why our network seems to be slower than it should I found some pretty bad packet loss (~25%). After further investigation and several experiments I did a measurment between the dom0 and one of the domUs: Server listening on UDP port 5001 Receiving 1470 byte datagrams UDP buffer size: 110 KByte (default) ------------------------------------------------------------ ------------------------------------------------------------ Client connecting to dom0, UDP port 5001 Sending 1470 byte datagrams UDP buffer size: 110 KByte (default) ------------------------------------------------------------ [ 3] local 192.168.1.2(domU) port 33817 connected with 192.168.1.100(dom0) port 5001 [ 4] local 192.168.1.2(domU) port 5001 connected with 192.168.1.100(dom0) port 48606 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 46.3 MBytes 38.7 Mbits/sec [ 3] Sent 33020 datagrams [ 3] Server Report: [ 3] 0.0-10.0 sec 46.2 MBytes 38.6 Mbits/sec 0.030 ms 89/33019 (0.27%) [ 3] 0.0-10.0 sec 1 datagrams received out-of-order [ 4] 0.0-10.2 sec 43.0 MBytes 35.3 Mbits/sec 13.074 ms 11575/42256 (27%) tl;dr: 27% packet loss from dom0 to domU with 50Mbit UDP packets. Same thing happens from anywhere in the network. The problem gets better for smaller bandwidths (0.047% for 5Mbit) and worse for higher (59% for 200Mbit) ones. I did increase the CPU-weight of the dom0, there is no swapping going on, and actual networking-hardware is not involved. I never expected Xen (or anything related) to drop packets, and I'm completly clueless what to try next.

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  • Ubuntu second static IP, ifconfig, /etc/network/interfaces

    - by Schmoove
    I would like to add a second static IP to my local Ubuntu 11.10 desktop machine and have it automatically available after rebooting. So far I am successfully using ifconfig to to temporarily set up an alias for my primary network interface: # ifconfig eth1:0 192.168.178.3 up # ifconfig eth1 Link encap:Ethernet HWaddr c8:60:00:ef:a3:d9 inet addr:192.168.178.2 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::ca60:ff:feef:a3d9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:61929 errors:0 dropped:0 overruns:0 frame:0 TX packets:64034 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:45330863 (45.3 MB) TX bytes:28175192 (28.1 MB) Interrupt:42 Base address:0x4000 eth1:0 Link encap:Ethernet HWaddr c8:60:00:ef:a3:d9 inet addr:192.168.178.3 Bcast:192.168.178.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 Interrupt:42 Base address:0x4000 However, when I add the following to /etc/network/interfaces, the alias is not up and running as expected after a reboot: # vi /etc/network/interfaces auto eth1:0 iface eth1:0 inet static address 192.168.178.3 netmask 255.255.255.0 I would like to know what to configure to get this to work. As a side note, I am running gnome shell.

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  • IP-dependent local port-forwarding on Linux

    - by chronos
    I have configured my server's sshd to listen on a non-standard port 42. However, at work I am behind a firewall/proxy, which only allow outgoing connections to ports 21, 22, 80 and 443. Consequently, I cannot ssh to my server from work, which is bad. I do not want to return sshd to port 22. The idea is this: on my server, locally forward port 22 to port 42 if source IP is matching the external IP of my work's network. For clarity, let us assume that my server's IP is 169.1.1.1 (on eth1), and my work external IP is 169.250.250.250. For all IPs different from 169.250.250.250, my server should respond with an expected 'connection refused', as it does for a non-listening port. I'm very new to iptables. I have briefly looked through the long iptables manual and these related / relevant questions: http://serverfault.com/questions/57872/iptables-question-forwarding-port-x-to-an-ssh-port-of-different-machine-on-the-n http://serverfault.com/questions/140622/how-can-i-port-forward-with-iptables However, those questions deal with more complicated several-host scenarios, and it is not clear to me which tables and chains I should use for local port-forwarding, and if I should have 2 rules (for "question" and "answer" packets), or only 1 rule for "question" packets. So far I have only enabled forwarding via sysctl. I will start testing solutions tomorrow, and will appreciate pointers or maybe case-specific examples for implementing my simple scenario. Is the draft solution below correct? iptables -A INPUT [-m state] [-i eth1] --source 169.250.250.250 -p tcp --destination 169.1.1.1:42 --dport 22 --state NEW,ESTABLISHED,RELATED -j ACCEPT Should I use the mangle table instead of filter? And/or FORWARD chain instead of INPUT?

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  • Window 7 Host does not answer to ping

    - by gencha
    Today I tried printing on a shared printer on one of our homegroup members. Sadly it did not work (printer marked as offline). Shortly after, I noticed I can't even ping the machine that owns the printer (I also can not remotely access it in any other way I've tried). Currently I'm trying to ping the machine from the router both computers are connected to (and my machine in question doesn't answer). I do receive the echo requests (as verified with WireShark). I also added a rule in the Windows Firewall to specifically allow ICMP echo requests, but that didn't change anything. I also tried netsh firewall set icmpsetting 8 enable, but that didn't change anything either. Completely disabling the Windows Firewall has no effect on the issue either. One has to wonder, where does Windows log when and why it ignored any incoming packets? How can I get to the bottom of this? Here are some ways I found to dig deeper into the issue: Enabling logging on the Windows Firewall Enabling Windows Filtering Platform Auditing Both methods at least give more insight into the issue. The plain log file is full of entries like this: 2011-11-11 14:35:27 DROP ICMP 192.168.133.1 192.168.133.128 - - 84 - - - - 8 0 - RECEIVE So the ICMP packets are being dropped as if that was intended. The Event Viewer now gives a little bit more details: The Windows Filtering Platform has blocked a packet. Application Information: Process ID: 4 Application Name: System Network Information: Direction: Inbound Source Address: 192.168.133.1 Source Port: 0 Destination Address: 192.168.133.128 Destination Port: 8 Protocol: 1 Filter Information: Filter Run-Time ID: 214517 Layer Name: Receive/Accept Layer Run-Time ID: 44 This same entry is always repeated with 2 points of information changing: Process ID: 420 Application Name: \device\harddiskvolume2\windows\system32\svchost.exe The service host with the PID 420 is the host for the following services: Windows Audio DHCP Client Windows Event Log HomeGroup Provider TCP/IP NetBIOS Helper Security Center Additionally, there is currently this problem with the same machine: Even though my network is set to be a "Home network", I am unable to create a new homegroup.

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  • Debian/Ubuntu - No network connection

    - by leviathanus
    I have a very weird situation on my Ubuntu 12.04 LTS Server. I can not access (ping) my gateway, although I believe my config is ok - I attach the outputs. Any hints where to look? (I changed the beginning of the IP to something different, just obfuscation) ping 5.9.10.129 PING 5.9.10.129 (5.9.10.129) 56(84) bytes of data. From 5.9.10.129 (5.9.10.129) icmp_seq=2 Destination Host Unreachable From 5.9.10.129 (5.9.10.129) icmp_seq=3 Destination Host Unreachable From 5.9.10.129 (5.9.10.129) icmp_seq=4 Destination Host Unreachable uname -r 3.2.0-29-generic ifconfig eth0 eth0 Link encap:Ethernet HWaddr 3c:97:0e:0e:54:d7 inet addr:5.9.10.142 Bcast:5.9.10.159 Mask:255.255.255.224 inet6 addr: fe80::8e70:5aff:feda:c4ac/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1216 errors:0 dropped:0 overruns:0 frame:0 TX packets:490 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:107470 (107.4 KB) TX bytes:34344 (34.3 KB) Interrupt:17 Memory:d2500000-d2520000 ip route default via 5.9.10.129 dev eth0 metric 100 5.9.10.128/27 via 5.9.10.129 dev eth0 5.9.10.128/27 dev eth0 proto kernel scope link src 5.9.10.142 route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 5.9.10.129 0.0.0.0 UG 1000 0 0 eth0 5.9.10.128 5.9.10.129 255.255.255.224 UG 0 0 0 eth0 5.9.10.128 0.0.0.0 255.255.255.224 U 0 0 0 eth0 iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination UPD: Eric, this is how routing information looks on a working server: 0.0.0.0 78.47.198.49 0.0.0.0 UG 100 0 0 eth0 78.47.198.48 78.47.198.49 255.255.255.240 UG 0 0 0 eth0 78.47.198.48 0.0.0.0 255.255.255.240 U 0 0 0 eth0 As I understand it, Hetzner tries to ensure security by this, so I can not take over an IP by changing my MAC. But this is another server, which has another netmask (255.255.255.240) UPD2: BatchyX, on the working server: 78.47.198.49 dev eth0 src 78.47.198.60 cache on the broken: 5.9.10.129 dev eth0 src 5.9.10.142 cache

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  • Cisco IOS BVI ACL: Only allow established UDP

    - by George Bailey
    Related: Cisco IOS ACL: Don't permit incoming connections just because they are from port 80 I know we can use the established keyword for TCP.. but what can we do for UDP (short of replacing a Bridge or BVI with a NAT)? Answer I found out what "UDP has no connection" means. DNS uses UDP for example.. named (DNS server) is lisenting on port 53 nslookup (DNS client) starts listening on some random port and sends a packet to port 53 of the server and notes the source port in that packet. nslookup will retry 3 times if necessary. Also the packets are so small that it does not have to worry about them coming in the wrong order. If nslookup receives a response on that port that comes from the servers IP and port then it stops listening. If the server tried to send two responses (for example a response and a response to the retry) then the server would not care if either of them made it because the client has the job to retry. In fact.. unless ICMP 3/3 packet gets through the server would not know about a failure. This is different from TCP where you get connection closed or timed out errors. DNS allows for an easy retry from the client as well as small packets.. so UDP is an excellent choice because it is more efficient. In UDP you would see nslookup sends request named sends answer In TCP you would see nslookup's machine sends SYN named's machine sends SYN-ACK nslookup's machine sends ACK and the request named's machine sends the response That is much more than is necessary for a tiny DNS packet

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  • Routing subnet over GRE tunnel

    - by eMgz
    Hi, Im trying to configure a GRE over IPSec connection between two subnets. The IPSec tunnel is opened and now I want to add a GRE tunnel over it: ip tunnel add GRE01 mode gre remote 10.244.0.1 local 10.244.245.32 ttl 255 ip link set GRE01 up ip addr add 10.244.248.126 dev GRE01 ip route add 10.244.248.125 dev GRE01 Now I have an interface GRE01 (ifconfig): GRE10 Link encap:UNSPEC HWaddr <h_addr> inet addr:10.244.248.126 P-t-P:10.244.248.126 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MTU:1476 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) And the following routes (ip route list): 10.244.248.125 dev GRE10 scope link <pub_subnet> dev eth0 proto kernel scope link src <pub_ip> default via <pub_gw> dev eth0 metric 100 As a last step, I need now to route my subnet over the tunnel: ip route add 10.245.1.224/28 10.244.248.125 However, I am getting the error Error: either "to" is duplicate, or "10.244.248.125" is a garbage. So, what I didn't understand is why I can't route my subnet over the tunnel, once the only route I have there says that it should route the tunnel IP over the GRE01 interface. Any hint? Thanks.

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  • NTOP gives warnings on startup

    - by FR6
    I just installed ntop 1.4.4 and when I start it, it give me infinite warnings "packet truncated": ... RRD_DEBUG: umask 0066 RRD_DEBUG: DirPerms 0700 THREADMGMT: RRD: Started thread (t2992630672) for data collection THREADMGMT[t2992630672]: RRD: Data collection thread starting [p30923] INIT: Created pid file (/var/run/ntop.pid) THREADMGMT[t3086329552]: ntop RUNSTATE: INITNONROOT(3) Now running as requested user 'nobody' (99:99) Note: Reporting device initally set to 0 [eth0] (merged) THREADMGMT[t3086329552]: ntop RUNSTATE: RUN(4) THREADMGMT[t2982140816]: NPS(1): Started thread for network packet sniffing [eth0] THREADMGMT[t2982140816]: NPS(eth0): pcapDispatch thread starting [p30923] THREADMGMT[t2982140816]: NPS(eth0): pcapDispatch thread running [p30923] THREADMGMT[t3047009168]: SIH: Idle host scan thread running [p30923] THREADMGMT[t3057499024]: SFP: Fingerprint scan thread running [p30923] **WARNING** packet truncated (8814->8232) **WARNING** packet truncated (10274->8232) **WARNING** packet truncated (8814->8232) **WARNING** packet truncated (8814->8232) ... Do I need to configure something? I tried to access the web interface (http://localhost:3000) but it does not work. Note: I'm on CentOS. EDIT: Not sure if it helps but there is my "ifconfig": eth0 Link encap:Ethernet HWaddr 00:16:76:BC:7E:77 inet addr:192.168.0.221 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::216:76ff:febc:7e77/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:15496640 errors:0 dropped:0 overruns:0 frame:0 TX packets:19256813 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:836230629 (797.4 MiB) TX bytes:608496148 (580.3 MiB) Memory:dffe0000-e0000000

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  • Need help with local network printing while using VPN on Ubuntu 10.10 desktop

    - by MountainX
    I can print to my HP printer via the LAN when I'm not connected to the VPN. When connected to the VPN, printing fails. OpenVPN 2.1.0 x86_64-pc-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [MH] [PF_INET6] [eurephia] built on Jul 12 2010 I can ping the printer while connected to the VPN: $ ping 192.168.100.12 PING 192.168.100.12 (192.168.100.12) 56(84) bytes of data. 64 bytes from 192.168.100.12: icmp_req=1 ttl=255 time=9.17 ms --- 192.168.100.12 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss... $ ping HpPrinter.local PING HpPrinter.local (192.168.100.12) 56(84) bytes of data. 64 bytes from HpPrinter.local (192.168.100.12): icmp_req=1 ttl=255 time=0.383 ms --- HpPrinter.local ping statistics --- 4 packets transmitted, 4 received, 0% packet loss... But here's the error when I try to print while connected to the VPN: hpijs[9990]: io/hpmud/jd.c 784: mdns lookup HpPrinter.local retry 1... ... hpijs[9990]: io/hpmud/jd.c 784: mdns lookup HpPrinter.local retry 20... hpijs[9990]: io/hpmud/jd.c 780: error timeout mdns lookup HpPrinter.local hpijs[9990]: io/hpmud/jd.c 88: unable to read device-id hp[9982]: io/hpmud/jd.c 784: mdns lookup HpPrinter.local retry 1... ... hp[9982]: io/hpmud/jd.c 784: mdns lookup HpPrinter.local retry 20... hp[9982]: io/hpmud/jd.c 780: error timeout mdns lookup HpPrinter.local hp[9982]: io/hpmud/jd.c 88: unable to read device-id hp[9982]: prnt/backend/hp.c 745: ERROR: open device failed stat=12: hp:/net/Officejet_Pro_L7600?zc=HpPrinter I am running iptables rules, but the problem doesn't appear related to the firewall. I've tested with no rules (i.e., no firewall). The printing problem happens when the VPN is connected. I can guess it is an mdns problem, but searching google about mdns didn't turn up anything that seemed related to this (at my level of knowledge). Any suggestions?

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  • High latency due to non-presence of a transit provider in my country

    - by nixnotwin
    My ISP, a state owned incumbent, buys bandwidth from different transit providers. Whenever it buys transits it announces only a specific prefix (in most cases a hitherto unused) through the new transit AS. For e.g. if it runs out of bandwidth, it buys bandwidth from a new transit and announces a new prefix through it, while the same prefix is not announced (or announced with lowest metrics, so that the routes are very rarely used) via the old transits which continue to provide bandwidth to it. I am a business customer, so I have a fiber based link to the ISP and a tiny subnet is given to me. The subnet which is provide to me is part of a prefix which is announced by the AS of a transit who, it seems, do not have a presence in my country. So when I do a trace the packets, when they leave my ISP's AS, they take about 275ms to reach the transit providers core router, which is located in USA (half the world away). Also for upstream traffic my ISP uses a transit provider (tier 1) who has a presence in my country. But the return path is always through the transit which is in USA. So, average latency is 400ms. All the users of other ISPs in my country discover my subnet via USA. Even the traffic from neighboring countries, from Europe (which is much nearer) follows the path via USA. Sites using CDNs also resolve to ips in USA. I have informed the ISP NOC about the issue and I have asked them to provide an ip subnet belonging to a prefix announced by a local transit (preferably a tier 1 transit provider) and I am waiting for a reply. My question: Is it a serious issue that I must follow up to get it resolved? When I compared the latency on other providers in my country, it is, in most cases, less than half of my ISPs latency. Why my ISP doesn't announce all its prefixes to all of its transit providers, so that the packets can take efficient and nearest routes to reach prefixes that originate within its network?

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  • Connect to Nonencrypted Wireless Network Using Ubuntu Commands

    - by Tim
    I failed to connect to an open i.e. nonencrypted wireless network using Ubuntu command lines. Here is what I did: $ sudo /etc/init.d/NetworkManager stop * Stopping network connection manager NetworkManager [ OK ] $ sudo /sbin/ifconfig wlan0 up $ sudo iwconfig wlan0 essid "Cavalier High-Speed 866-4-CAVTEL" $ sudo dhclient wlan0 There is already a pid file /var/run/dhclient.pid with pid 10812 killed old client process, removed PID file Internet Systems Consortium DHCP Client V3.1.1 Copyright 2004-2008 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/sw/dhcp/ wmaster0: unknown hardware address type 801 wmaster0: unknown hardware address type 801 Listening on LPF/wlan0/00:0e:9b:cd:4e:18 Sending on LPF/wlan0/00:0e:9b:cd:4e:18 Sending on Socket/fallback DHCPREQUEST of 192.168.1.67 on wlan0 to 255.255.255.255 port 67 DHCPREQUEST of 192.168.1.67 on wlan0 to 255.255.255.255 port 67 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 7 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 8 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 12 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 21 DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 6 No DHCPOFFERS received. Trying recorded lease 192.168.1.67 PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data. --- 192.168.1.1 ping statistics --- 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms Trying recorded lease 192.168.1.45 PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data. --- 192.168.1.1 ping statistics --- 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms No working leases in persistent database - sleeping. $ sudo /sbin/iwconfig wlan0 wlan0 IEEE 802.11bg Mode:Managed Frequency:2.422 GHz Access Point: Not-Associated Tx-Power=27 dBm Retry min limit:7 RTS thr:off Fragment thr=2352 B Encryption key:off Power Management:off Link Quality:0 Signal level:0 Noise level:0 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 I was wondering what the problem is and how I can do it right? Thanks and regards!

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  • Wake on LAN Problem

    - by Caley Woods
    I'm working to get wake on lan (wol) working so that we can do some power management at my workplace. I've enabled WOL on a test laptop running Win 7 x64 and put it to sleep and hibernate both with no luck. I'm using a 3rd party utility and I've ran wireshark on the test laptop with it booted up and I can see the WOL packets coming in and the machine refuses to wake from sleep or hibernate. I thought maybe it was the computer I was using so I had another Win 7 x64 laptop nearby and I tried it, same scenario. We're in a cisco environment and I believe I gotten all the pieces in place since I'm seeing the WOL packets come through. I've tested two machines on the same subnet to eliminate the possibility of a misconfiguration on the switch, this also has the same behavior. The laptop models are a Compaq 6510b and 6730b. Is there something I'm missing? I'm trying this across UDP port 50200 since that's the port the actual management system will use after I get it working.

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