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Re: [Xen-users] question on bridged OR routed configuration & public IP

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] question on bridged OR routed configuration & public IP addresses
From: Craig Thompson <craig@xxxxxxxxxxxxxxx>
Date: Wed, 13 Feb 2008 17:42:29 -0500
Cc: Steven Timm <timm@xxxxxxxx>
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CENTOS USERS BEWARE!

Interestingly enough, I've made some headway.

After beating my head into the wall repeatedly, I got an inspiration, from the Lord no doubt.

In my ifconfig, I consistently saw a xenbr0 listed even though CentOS does not USE that bridge. It sets up and uses virbr0 by default.

Don't ask me why the good folks at RedHat chose to do this.

I thought, "Why don't I pretend that virbr0 does not exist? Pretend that xenbr0 is really the bridge to use."

So I changed my /etc/libvirt/qemu/networks/default.xml file to use the name xenbr0 instead of virbr0 (default).

I also changed my guest config file in /etc/xen to explicitly use 'xenbr0' in the vif statement.

I rebooted, brought up my guest, and voila!  It worked.

I can ping my default gateway from dom0.  I can ping my guest OS from dom0.

I can ping dom0 from domU.  I can ping the Internet from domU.

NOW, I beg the question, WHY did RedHat do this? Why use virbr0 by default if it doesn't work?

My routing table still looks the same as it did before:

192.168.1.0     0.0.0.0         255.255.255.0   U       0 0 0 xenbr0
192.168.1.0     0.0.0.0         255.255.255.0   U       0 0 0 eth0
169.254.0.0     0.0.0.0         255.255.255.0   U       0 0 0 eth0
0.0.0.0         192.168.1.1     0.0.0.0         UG      0 0 0 xenbr0

So that routing table WORKS if the proper bridge is utilized.

I hope this helps someone else.

LT

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