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There are 3 machines in my home network, running WinXP, Ubuntu 8.04.01, PCLinuxOS..lets call them win, ubuntu, pclinux. All of them can access internet flawlessly except one case when I'm ...
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  1. #1
    Just Joined!
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    Jul 2008
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    ssh connection drops once in a while


    There are 3 machines in my home network, running WinXP, Ubuntu 8.04.01, PCLinuxOS..lets call them win, ubuntu, pclinux. All of them can access internet flawlessly except one case when I'm trying to access my office machine (lets call it office) running Fedora thru ssh - connection works, but couple of "ls -la" and connection hangs up - just freezes. Here is the set of tests I've done:

    1. "PCLinux" can ssh to "office" with no issue
    2. "Win" can ssh thru putty to "office" with no issue
    3. "Ubuntu" can ssh but connection dies once in a while
    4. I tried Ubuntu live CD at home -> same problem
    5. I tried Ubuntu live CD in the office - works flawlessly

    Here is the result of "uname -a" for Ubuntu machine
    Code:
    alxlabs@alxlabs-desktop:~$ uname -a
    Linux alxlabs-desktop 2.6.24-16-generic #1 SMP Thu Apr 10 13:23:42 UTC 2008 i686 GNU/Linux
    Here is the results of "ifconfig" for Ubuntu machine
    Code:
    alxlabs@alxlabs-desktop:~$ ifconfig
    eth2      Link encap:Ethernet  HWaddr 00:0e:0c:9b:e3:03  
              inet addr:192.168.2.12  Bcast:192.168.2.255  Mask:255.255.255.0
              inet6 addr: fe80::20e:cff:fe9b:e303/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:57743848 errors:0 dropped:0 overruns:0 frame:0
              TX packets:67933535 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000 
              RX bytes:4032463599 (3.7 GB)  TX bytes:3768227628 (3.5 GB)
    
    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:39883 errors:0 dropped:0 overruns:0 frame:0
              TX packets:39883 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:0 
              RX bytes:5573203 (5.3 MB)  TX bytes:5573203 (5.3 MB)

    Here is "uname -a" for PCLinux machine
    Code:
    Linux localhost 2.6.18.8.tex5 #1 SMP Thu May 10 11:36:58 WST 2007 i686 Intel(R) Core(TM)2 Duo CPU     T7100  @ 1.80GHz GNU/Linux
    Here is "ifconfig" from mPCLinux machine
    Code:
    eth0      Link encap:Ethernet  HWaddr 00:19:B9:81:F5:D1
              inet addr:192.168.2.101  Bcast:192.168.2.255  Mask:255.255.255.0
              inet6 addr: fe80::219:b9ff:fe81:f5d1/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:97 errors:0 dropped:0 overruns:0 frame:0
              TX packets:130 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000
              RX bytes:18233 (17.8 KiB)  TX bytes:17323 (16.9 KiB)
              Interrupt:17
    
    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: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)
    Additional observations:

    1. tracert from "Ubuntu" to "office" never finds the route
    2. tracert from "PCLinux" to "office" never finds the route
    Code:
    alxlabs@alxlabs-desktop:/root$ sudo tracert mail.frescomicrochip.com -m 255
    traceroute to mail.frescomicrochip.com (216.234.32.26), 255 hops max, 40 byte packets
     1  192.168.2.1 (192.168.2.1)  0.421 ms  0.410 ms *
     2  * * *
     3  * * *
     4  * * *
     5  * * *
     6  * GE0-2.WANB-TOROONXN.IP.GROUPTELECOM.NET (66.59.191.37)  59.000 ms  61.596 ms
     7  POS2-0.PEERA-TOROONXN.IP.GROUPTELECOM.NET (66.59.191.150)  78.341 ms  78.520 ms  80.368 ms
     8  if-14-2.core1.TNK-Toronto.teleglobe.net (216.6.112.41)  85.114 ms  88.153 ms  92.979 ms
     9  if-0-0.ihar1.TGS-Toronto.teleglobe.net (216.6.122.50)  108.075 ms  109.801 ms  109.809 ms
    10  ix-0-3.ihar1.TGS-Toronto.teleglobe.net (209.58.16.18)  111.164 ms  113.659 ms  125.534 ms
    11  e0-2.nc-frt-bas1.rtr.connection.ca (216.234.47.214)  127.013 ms  127.258 ms  96.280 ms
    12  39.167.207.205.rev.connection.ca (205.207.167.39)  98.006 ms  81.851 ms  82.726 ms
    13  * * *
    14  * * *
    15  * * *
    16  * * *
    17  * * *
    18  * * *
    ......
    ......
    2. tracert from "office" to "Ubuntu" cannot make even a single hop
    Code:
    traceroute to alxlabs.27south.com (216.99.99.169), 30 hops max, 38 byte packets
     1  * * *
     2  * * *
     3  * * *
     4  * * *
     5  * * *
    From all of the machines internet access is OK.

    Just to recap: problem is that I can ssh from Win, PCLinux to office machine and cannot do the same from Ubuntu. Any ideas?

  2. #2
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    Some additional debugging revealed that
    1. "office" machine is not pingable from both "ubuntu" and "win" machines (as well as PCLinux) which may lead to MTU-related issues
    1. Changing an MTU size on "Ubuntu" does not help.

  3. #3
    Linux Guru Lazydog's Avatar
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    Jun 2004
    Location
    The Keystone State
    Posts
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    First things first.
    Because you can't ping or traceroute to the office computer from home has nothing to do with the MTU's. It is most likely because of the firewall that is located at the office not allowing this type of traffic access. Same with the ping from the office to your home (totally normal).

    You stated that you changed your MTU's on the ubuntu box, please restore them if you have not done this already.

    Now that that is out of the way.

    The windows box and the pclinux box have no issues connecting and holding a connection to your office machine. Are you doing the same test/processes from both of these boxes that you are doing on the ubuntu? That would be the only fair way to know that it is just ubuntu having an issue.

    On the information you have posted the problem is totally with your ubuntu box. What does the ssh config look like? Maybe compare ubuntu to pclinux ssh config file.

    Regards
    Robert

    Linux
    The adventure of a life time.

    Linux User #296285
    Get Counted

  4. #4
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    Thanks Robert...

    Actually is not limited to ssh - all services behave the same, even web. From the pclinuxOS and Win boxes I can use a corporate webmail and cannot thru Ubuntu - it loads half of the page and then dies, no dependancy on browser. Problem is not limited to Ubuntu as well - I tried bunch of LiveCDs - some of them work OK (CentOS for example) and some of them not (Slax) with exactly same symptoms. No dependancy on the computer itself - i tried bunch of the PCs....The only dependancy I see is just the OS itself - so far it works perfectly fine with WinXP, CentOS, PCLinux and fails with Ubuntu and Slax with identical procedure (as identical as it could be with the LiveCD) on the same hardware and same connetcion with identical issue - connection drops after 8-10K of transfer for all services, ssh is just an example. Problem should be somewhere on the ISP side....I just thought that if it works with PCLInux/CentOS/WinXP etc then it should be an easy way to make it work with Ubuntu as I use it at home.

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