Network drops in virtualized environment

Unanswered Question
Apr 28th, 2009

I've noticed a spike in the reoccuring problem of the network forgetting

the location of virtual machines within the Xen infrastructure. My VMWare Admin

has also seen this occur many times with VMware virtual machines, which

leads me to believe its not an issue with the server side.

The symptoms are networking drops, but just for a particular VM. I've

performed packet captures and it looks like traffic does not even get

sent to the Xen server itself for that VM, nevermind passed into the VM

itself. It doesn't matter if I'm initating traffic from the same subnet

or a different network; traffic doesn't get to the VM. Thus, I think

this is a layer 2 issue. I'm guessing the switches forget the MAC

address location.

My resolution for when this occurs is to migrate the VM to another Xen

server, thus causing the network to relearn its location. This is also

how the other admin fixes this issue with VMware VM's.

Has anyone else experienced this? This seems to occur with VMs that have very low traffic profiles...

I have this problem too.
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rshum Wed, 04/29/2009 - 10:03

Are you using an etherchannel to connect to the host machine or is it 1 physical network port?

If it connection drops can you do a sho mac add to see where the switch OS thinks the MAC address should be?


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