The upgrade process of a Xen VM host server is exactly the same as upgrading a regular OES 2 server to OES 11, with one important difference. After the server is updated, the Xen Hypervisor might have an incorrect network configuration that prevents Xen from running.
SUSE has improved the network configuration in SLES 11. If you install SLES 11 SP4 and configure Xen, you get a bridged setup through YaST. However, if you upgrade from SLES 10 to SLES 11, the upgrade does not configure the bridged setup automatically. Until the bridged setup is configured for SLES 11, your Xen VM guest servers will not run. Be sure to set up the bridge using YaST as outlined in Section 9.4, Setting Up Bridging After the Upgrade.
NOTE:If you have an advanced network configuration, refer to the SLES documentation for instructions on configuring your network settings during the upgrade. The instructions in this section assume a single network interface.