This article describes how to validate if XenServer is using Bridge or vSwitch for the network stack.
By default, XenServer 6.x uses vSwitch as the network stack when the host is installed. At some point, the XenServer administrator might have changed the network stack to Bridge.

When attempting to add a new host created with a default install to a resource pool, that is configured to use Bridge as the network stack, the following message appears and the host does not join the pool:
“This server’s network backend is different from the master’s”

Instructions

1. Run the following command in the command line interface of both the new pool and the host pool, to determine which network stack each pool is using:
   more /etc/xensource/network.conf

2. When the incorrect network stack is determined, run the following commands to change the network stack:
   xe-switch-network-backend bridge (changes to the Linux-based stack)
   xe-switch-network-backend openvswitch (changes to the more robust vSwitch stack)