Re: [Xen-users] Trouble with manual bridging on Xen3/CentOS 5

[Digimer <linux@xxxxxxxxxxx>]

On 04/30/2011 08:47 PM, Teck Choon Giam wrote:
> Pasi is right about to use system network configuration so that xend
> and system network are separated.  Can you explain how it was bugged?
> Is it sometimes get set and sometimes not?  Have you try to give a
> small sleep interval such as 3 seconds before setting the related mtu?
> 
> Thanks.

Sure.

  I've got three interfaces in my server;
- eth0; Internet-facing, bridged as xenbr0
- eth1; Storage network, not bridged or used by any domU.
- eth2; Back-channel/internal network, bridged as xenbr2, used by some domU.

  I had a patch[1] in xen-network-common.sh's setup_bridge_port()
function that would look at the $dev passed in, parse it and pull the
MTU from the corresponding bridge. The bug was that this $dev matched
the ethX device in the domU rather than the bridge, so when the second
interface (xenbr2 <-> domU's eth1) would look for the MTU of 'xenbr1',
which didn't exist.

  In trying to fix that with Paolo's help, I found that it stopped
updating the vif0.0 and vif2.0 used by dom0. In trying to find out why,
Pasi mentioned that I should move the bridge's outside of Xen, which I
did now. With the bridges outside of xen, they were set to the MTU of
dom0's corresponding ethX devices on boot. Then I could focus on getting
the domU vif's at the corresponding bridge's MTU and now you know the
rest of the story. :)

Digimer

1. https://bugzilla.redhat.com/attachment.cgi?id=492964&action=diff

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