RE: [Xen-users] XEN - Broadcom issue: survey

["Boudreau Luc" <luc.boudreau@xxxxxxxxxxxx>]

Hmm, it's a production server so I wouldn't want to change the IP's... Also, I 
fear it might not be a 'network related' issue at all. We were able to get 
messages about IRQ conflicts between a domU and dom0 because one of the domU 
has a pci nic given to it. The device gets IRQ 16, but dom0 also uses this 
channel for a nic. It might be the source of this unstability. I've created 
another discussion thread on this issue : "IRQ conflict between dom0 and domU". 
I'm investigating on this now. It looks more probable than just a plain bridge 
config issue.

Any insights on how to make sure the same IRQ doesn't get attributed twice ??


-----Message d'origine-----
De : Steven Smith [mailto:sos22@xxxxxxxxxxxxxxxx] De la part de Steven Smith
Envoyé : 28 novembre 2007 15:57
À : Boudreau Luc
Cc : xen-users@xxxxxxxxxxxxxxxxxxx; sos22-xen@xxxxxxxxxxxxx
Objet : Re: [Xen-users] XEN - Broadcom issue: survey

> A bit more information on this issue. We decided to buy another NIC 
> (other than Broadcom).  The problem still happens, thus eliminating 
> the NIC problem.
Okay, so it's not the NIC.  That suggests that the problem is somewhere between 
dom0 and domU.  It'd be worthwhile trying to eliminate the bridge before going 
further, so try something like this:

# brctl delif xenbr0 tap0
# ifconfig tap0 up 192.168.97.1

as root in dom0, and then bring the interface up on a static IP like
192.168.97.2 inside the guest.  You need to choose IP addresses so that they 
don't collide with anything else you're using, and it needs to be a different 
network to anything else you want to talk to.  Test whether domU experiences 
problems talking to dom0 on 192.168.97.1; if it doesn't, that suggests that the 
problem is with the bridge.

Having said that, this all sounds like an MTU issue.  It would be worth 
checking what MTUs you're using on the relevant interfaces.
ifconfig can tell you this on Linux, and there's a description of the windows 
equivalent at http://www.pctools.com/guides/registry/detail/280/ .  You 
probably want to look at eth0, xenbr0, and tap0 in dom0, and the relevant 
interface in the guest.  All of the MTUs should match up.

Steven.

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