XEN: Changing the network bridge for DomU's

This document (7000175) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 10 Service Pack 1

Situation

An existing Xen DomU needs to change the network bridge it is attached to.

Resolution

There are three methods to change the network bridge. Please select the method that is appropriate for your configuration.

method 1: for unamanged domains
This method is used for unmanaged domains; that is, DomU's that have not been managed by "virt-manager", "xm" commands or "YaST" to make hardware configuration changes
Replace SLES10 with the name of your DomU

Navigate to /etc/xen/vm in a console
Locate the name of the configuration file for the DomU
Backup the configuration file in case a mistake is made
Open the file for editing
Locate the line reading "vif", it may look like the following:
vif=[ 'mac=00:16:3e:5f:e7:f2', ]
Add "bridge=BRIDGE_NAME" to the line. For example, to have the virtual interface attached to "xenbr2":
vif=[ 'mac=00:16:3e:5f:e7:f2,bridge=xenbr2', ]
Save and close the file
Test the configuration file
xm create -c SLES10

method 2: managed domains configured through legacy files
This method uses method 2, but imports the configuration file. This method is acceptable as long as configuration changes for the virtual hardware have only been done through the configuration files and is recommended for most use cases.
Replace SLES10 with the name of your DomU

Follow method 1, until you are satified that the changes work as desired
Import the configuration file into the management database.
xm new -f SLES10
Start your DomU as normal

method 3: use managed configuration
This method is more advanced and is only useful in situtations where the virtual hardware has been modified through "xm" commands, "virt-manager" or YaST.
Replace SLES10 with the name of your DomU

Export the configuration from the management database
xm list -l SLES10 > SLES10.py
Backup SLES10.py, in case it is needed again.
Open the file for editing
Locate the following (or something similar)
(device

(vif

(uuid fae123bf-d267-c396-a2b5-b3488b82d5e7)

(script vif-bridge)

(mac 00:16:3e:1a:e5:1d)

(model rtl8139)

(type ioemu)

(backend 0)

)

)
Add (bridge BRIDGE_NAME) after the (vif declaration. For example:
(device

(vif

(uuid fae123bf-d267-c396-a2b5-b3488b82d5e7)

(script vif-bridge)
(bridge br1)

(mac 00:16:3e:1a:e5:1d)

(model rtl8139)

(type ioemu)

(backend 0)

)

)
Save and close the file
Reimport the configuration into the management database
xm new -F SLES10.py
Test the DomU
Repeat steps 3 through 7 until satisfied that the configuration changes worked

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.