Xen users - Feb 2012 - Creating network bridge without IP address

Hi everyone!

I have the following setup:

domain0
|-domU1
|-domU2
|-domU3

I am running this with libvirt on a XEN server. Right now the server is
connected to our office network, but later it will be in a hosted environment. I
need domU1 and domU3 to have a public IP, and all of the domUs and the dom0
should have an internal IP address to communicate with each other. So this is
what I would like to achieve:

domain0 
   192.168.122.1
|-domU1
   192.168.122.2
   192.168.1.45 (later this will be changed to the public IP)
|-domU2
   192.168.122.3
|-domU3
   192.168.122.4
   192.168.1.46 (this will also be changed to a public IP)

On domain0 I have the following network interfaces:

br0       Link encap:Ethernet  HWaddr 54:04:a6:66:c4:be  
          inet addr:192.168.1.44  Bcast:192.168.1.255  Mask:255.255.255.0
virbr0    Link encap:Ethernet  HWaddr 52:54:00:fe:88:0c  
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0

This way everything is working fine, except that I don''t want domain0
to have a public IP (which is 192.168.1.44 in this case)

So is it possible somehow to setup br0 on domain0 without it having an IP
address?

Thank you,
Zoltan Lippai

Zoltan Lippai wrote:
>So is it possible somehow to setup br0 on domain0 without it having 
>an IP address?
Yes, it is very easy - but you have missed out two very important 
bits of information :
1) What OS/Distro are you using for Dom0 ?
2) How are you setting up the bridges ?

Using the network-scripts in Xen to setup bridges is deprecated in 
favour of using the OS tools to do it. In Debian it''s as easy as 
putting this in your /etc/network/interfaces file :
auto eth0
iface eth0 inet static
   bridge_ports peth0
   address 192.168.x.y
   netmask 255.255.255.0
   gateway 192.168.x.z

If you don''t want an IP on the bridge, then simply omit the lines 
adding it, so you just have :
auto eth0
iface eth0 inet static
   bridge_ports peth0

NB - for my setup, I''ve configured the NIC to have the name peth0 
using the persistent rules in /etc/udev/rules.d. That allows me to 
call the bridge eth0 which means it looks just like a normal 
interface in scripts etc. At work where I have multiple bridges, I 
tend to use [p]ethint, [p] ethback, [p] ethext, and so on so it;s 
clear what each is connected to.

-- 
Simon Hobson

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