CentOS virt - Oct 2011 - Emergency help needed on host network randomly stop working.

Hi,
  This is a Centos 5.5 host with one xen guest.
  About 2 weeks ago, the host randomly lost network connection. By
this I mean I could not connect to the services on it, or ping it.
Also was the status of the guest.
  From serial console, I connected to the host, trying to see what
happened. No clue (any error messages) in messages or dmesg.
ifdown/ifup the interface did not help, either. Only rebooting was my
only choice.
  Searching through Google, I got the information that some other guys
met similar problem, and resolved by setting stp on with the bridge
interface.
  I set it, too. And the problem still occurs.
  Any idea what I should check now?
  Thanks.
-- 
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Hi,

On Wed, Oct 12, 2011 at 10:43 AM, Magicloud Magiclouds
<magicloud.magiclouds at gmail.com> wrote:
> Hi,
> ?This is a Centos 5.5 host with one xen guest.
> ?About 2 weeks ago, the host randomly lost network connection. By
> this I mean I could not connect to the services on it, or ping it.
> Also was the status of the guest.
> ?From serial console, I connected to the host, trying to see what
> happened. No clue (any error messages) in messages or dmesg.
> ifdown/ifup the interface did not help, either. Only rebooting was my
> only choice.
> ?Searching through Google, I got the information that some other guys
> met similar problem, and resolved by setting stp on with the bridge
> interface.
> ?I set it, too. And the problem still occurs.
> ?Any idea what I should check now?
So I assume that the problem occurs just with the xen domU and not
with the dom0? And your solution is to reboot the domU (not dom0)?

With loosing network you mean you cannot ping your gateway ip and/or
you   cannot ping the domU from your gw?

You are running the latest kernel/xen packages provided by centos on
your dom0 and domU?

How have you configured network on this server, can you post your
configs (vif line in dom0 config aand newtork config files from the
domU)?

And you are sure you have an unique MAC address in your LAN for your domU?

Best,
Peter

On Wednesday 12 October 2011 03:43, the following was written:
>  Hi,
>    This is a Centos 5.5 host with one xen guest.
>    About 2 weeks ago, the host randomly lost network connection. By
>  this I mean I could not connect to the services on it, or ping it.
>  Also was the status of the guest.
>    From serial console, I connected to the host, trying to see what
>  happened. No clue (any error messages) in messages or dmesg.
>  ifdown/ifup the interface did not help, either. Only rebooting was my
>  only choice.
>    Searching through Google, I got the information that some other guys
>  met similar problem, and resolved by setting stp on with the bridge
>  interface.
>    I set it, too. And the problem still occurs.
>    Any idea what I should check now?
I am no expert but it sounds like you might be in the early stages of hardware 
failure.

Next time this system stop responding check the following:

1. System interface state
2. Connected switch interface

If the switch shows down but the system shows up I wold start by replacing the 
NIC on the system.


-- 

Regards
Robert

Linux
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Linux User #296285
Get Counted
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On 10/12/11 12:43 AM, Magicloud Magiclouds wrote:
> Hi,
>   This is a Centos 5.5 host with one xen guest.
>   About 2 weeks ago, the host randomly lost network connection. By
> this I mean I could not connect to the services on it, or ping it.
> Also was the status of the guest.
>   From serial console, I connected to the host, trying to see what
> happened. No clue (any error messages) in messages or dmesg.
> ifdown/ifup the interface did not help, either. Only rebooting was my
> only choice.
>   Searching through Google, I got the information that some other guys
> met similar problem, and resolved by setting stp on with the bridge
> interface.
>   I set it, too. And the problem still occurs.
>   Any idea what I should check now?
>   Thanks.
When outage occurs, from the host these might be good things to look at
and/or share with the list:

ip link
brctl show
arp -n (arp -n from your next-hop router too)
tcpdump -ln -i peth0 (try some activity; e.g. ping out to router, ping
in from router)
tcpdump -ln -i br0 (more activity)

Depending on your xen bridge setup the bridge might be named eth0 or
virbr0; peth0 might be different too.

Eric