Re: [Xen-users] bridge interfaces in dom0

["Steve Feehan" <sfeehan@xxxxxxxxx>]

On 11/10/06, Jaroslaw Zdrzalek <jz@xxxxxxxxxx> wrote:
> Am Donnerstag 09 November 2006 23:11 schrieb Steve Feehan:
> In dom0 you have physical interfaces, the naming is pethX,
> and you have virtual ones, which are these named ethX.
> Neighter the physical ones nor the bridges shoud have ip
> configured. If you really nead ip traffic going from dom0 to
> your domUs configure ip on ethX in Dom0 und DomU.
> It is sufficient.
Yes, I understand this.

> > I thought that the interface would have to merely be "up" but not
> > necessarily have an
> > IP address configured since bridging is done at layer 2. But alas, if
> > I don't configure
> > an IP address on dom0 the bridge seems to not be usable from a guest domain.
> It shoult not happen. Did you have read the howto for multiple bridges:
> at the bottom, starting with:
> "With Xen 3.0 the best method for additional bridges is t..."
> http://wiki.xensource.com/xenwiki/XenNetworking
Yes, that is what I based my configuration on. Here is my custom network script:

#!/bin/sh
/etc/xen/scripts/network-bridge $@ bridge=xenbr0 netdev=eth0 vifnum=0
/etc/xen/scripts/network-bridge $@ bridge=xenbr1 netdev=eth1 vifnum=1
/etc/xen/scripts/network-bridge $@ bridge=xenbr3 netdev=eth3 vifnum=3

And this works fine as long as the virtual interfaces (eth0, etc.) have IP
addresses configured.

Actually, let me state this more completely:

My custom network-script works if the phsical interfaces have IP addresses
BEFORE xen starts.

And when I say it works, I mean that:

* bridges are created
* the virtual interfaces exist in the guests
* AND they are usable.

It's the last point that is the important part. When I don't configure
IP addresses
on the physical interfaces in dom0 BEFORE starting Xen the bridges are still
created and the virtual interfaces exist in the guests, but they're
not usable. And
by not usable I mean if I configure them with an IP address and try to ping from
the guest I get "network unreachable" errors. At least, that is what I
recall. This
is all getting a bit fuzzy in my memory after the long weekend. I need
to go back
and reproduce the problem again.

> > My motivation for this is that dom0 has 4 interfaces which could be on
> > 4 networks. I
> > didn't want to assign IP addresses for dom0 on ALL of these networks.
> You need 4 bridges, no need to configure any ip in dom0
Yes, this is what I think too. I will try and reproduce the problem
and follow up with
the result.

Thanks,

--
Steve Feehan

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