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I'm having a problem with a Debian 6 VM server where it looses network connectivity and doesn't come back (server does not respond to pings, and can't connect to any services). This is a wired network connection in a data center where the network is up when the problem occurs.

When logged into the console, I confirm that the server doesn't seem to have network conectivity (can't ping ip 8.8.8.8 for example). All services are running though (mysql, Apache, SSH, etc). There are some errors in /var/log/kern.log, but not sure these are related to the problem:

Jan  5 01:43:41 vm2 kernel: [12179513.252191] INFO: task mysqld:1369 blocked for more than 120 seconds.
Jan  5 01:43:41 vm2 kernel: [12179513.253230] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jan  5 01:43:41 vm2 kernel: [12179513.254237] mysqld        D ffff8801b46de9f0     0  1369   1179 0x00000000
Jan  5 01:43:41 vm2 kernel: [12179513.254243]  ffff8801b46de9f0 0000000000000286 ffff8801fd105e18 000000010000000e
Jan  5 01:43:41 vm2 kernel: [12179513.254250]  ffff8801f750f478 ffff8801fd105e18 000000000000f9e0 ffff8801fd105fd8
Jan  5 01:43:41 vm2 kernel: [12179513.254253]  00000000000157c0 00000000000157c0 ffff8801fd1c5bd0 ffff8801fd1c5ec8
Jan  5 01:43:41 vm2 kernel: [12179513.254259] Call Trace:
Jan  5 01:43:41 vm2 kernel: [12179513.254270]  [<ffffffff810b61e1>] ? wait_on_page_writeback_range+0xce/0x11b
Jan  5 01:43:41 vm2 kernel: [12179513.254282]  [<ffffffffa001fe20>] ? log_wait_commit+0xbf/0x112 [jbd]
Jan  5 01:43:41 vm2 kernel: [12179513.254288]  [<ffffffff81066332>] ? autoremove_wake_function+0x0/0x2e
Jan  5 01:43:41 vm2 kernel: [12179513.254296]  [<ffffffff8130f142>] ? _spin_unlock_irqrestore+0xd/0xe
Jan  5 01:43:41 vm2 kernel: [12179513.254303]  [<ffffffffa00303f8>] ? ext3_sync_file+0x94/0xc8 [ext3]
Jan  5 01:43:41 vm2 kernel: [12179513.254309]  [<ffffffff8110d6e0>] ? vfs_fsync_range+0x73/0x9e
Jan  5 01:43:41 vm2 kernel: [12179513.254312]  [<ffffffff8110d78a>] ? do_fsync+0x28/0x39
Jan  5 01:43:41 vm2 kernel: [12179513.254316]  [<ffffffff8110d7b9>] ? sys_fsync+0xb/0x10
Jan  5 01:43:41 vm2 kernel: [12179513.254319]  [<ffffffff8130f6fa>] ? error_exit+0x2a/0x60
Jan  5 01:43:41 vm2 kernel: [12179513.254323]  [<ffffffff81011b42>] ? system_call_fastpath+0x16/0x1b 

When the problem happens, the network interfaces are up (I checked ifconfig, all interfaces looked normal). I also check iptables, and verify there were no rules that would block anything. I also try running /etc/init.d/networking/restart, but that does not fix the problem. The only thing I've found that fixes the problem is rebooting.

Hoping for some advice on things I can check to help troubleshoot this problem.

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1 Answer 1

I have seen similar problems where the interface is up for a while and then went down. In our case there was some mismatch between the ethernet card of a host and the switch on which they are connected.

What I did was to use ethtool to set the card half duplex:

ethtool -s eth0 speed 100 duplex half

and check if that solves the problem. That is of course sub-optimal, but if it pinpoints the problem you can then change the ethernet (add a card) or switch switches.

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