CentOS virt - Mar 2008 - Re: CentOS-virt Digest, Vol 7, Issue 22

Already reported....

http://bugs.centos.org/view.php?id=2516


 >Subject: RE: [CentOS-virt] xenbr0 isn't created anymore
 >To: <centos-virt at centos.org>
 >Message-ID:
 >	<E2BB8074E5500C42984D980D4BD78EF9022A704E at MFG-NYC-EXCH2.mfg.prv>
 >Content-Type: text/plain;	charset="us-ascii"
 >
 >Kai Schaetzl wrote:
 >> 
 >> Somehow I managed to disable the creation of xenbr0 on boot-up of the
host
 >> system. CentOS 5 with standard CentOS Xen. 
 >> I changed all Xen VMs to use xenbr0 instead of virbr0 and disabled 
 >> virtlibd. Works fine. But when I later restarted the machine I found
that
 >> all networking for guests had gone. On inspection there's no
xenbr0
 >> created anymore. I can get it up by stopping network (or eth0) and
then
 >> running /etc/xen/scripts/network-bridge start
 >> xend-config.sxp still has (network-script network-bridge), logging
shows
 >> no problems. It seems that the network-bridge script simply
doesn't run,
 >> but why? I can't see any init script or so that might run it, so I
assume
 >> it's xend doing that, but there's no error in any log.
 >
 >Kai,
 >
 >Snooping around I found this in /etc/xen/qemu-ifup:
 >
 >#
 ># Old style bridge setup with netloop, used to have a bridge name
 ># of xenbrX, enslaving pethX and vif0.X, and then configuring
 ># eth0.
 >#
 ># New style bridge setup does not use netloop, so the bridge name
 ># is ethX and the physical device is enslaved pethX
 >#
 ># So if...
 >#
 >#   - User asks for xenbrX
 >#   - AND xenbrX doesn't exist
 >#   - AND there is a ethX device which is a bridge
 >#
 ># ..then we translate xenbrX to ethX
 >#
 ># This lets old config files work without modification
 >
 >So it turns out Xen networking changed in current releases and they never
 >updated their Wiki.
 >
 >Now I am not sure how the vif0.X and vethX interfaces fit into the
 >picture here... Maybe these are no longer used?
 >
 >vifX.Y interfaces are still used though for linking domU interfaces
 >with the physical interface.
 >
 >
 >-Ross
 >
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Hristo Benev wrote on Sat, 29 Mar 2008 02:39:42 +0200 (EET):
> Already reported....
That looks like something different. Maybe related, but not the same 
problem. Note, I can create VMs with virt-manager. Unfortunately, the 
reporter gave the perfect explanation "it doesn't work", so I
don't know
what he's experiencing. I suppose he may have switched off libvirtd and 
then virt-manager indeed might not be able to find interfaces.

The problem I describe here happens when starting up xend. Under some not 
yet known circumstances the network-bridge script won't be able to 
determine the interfaces to juggle with because the output of ip route 
list is not what it expects.

Kai

-- 
Kai Sch?tzl, Berlin, Germany
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