I had an issue with a 4 server XenServer deployment in which the underlying network configuration was changed, making the pool master unavailable by the other members of the pool. These were freshly installed so I had no concerns with data on the local storage of the XenServers, although using this method should not affect any data resident there (YMMV). Reconfiguring the network on the pool master wasn't a problem but on the 3 member machines, there were no network interfaces visible in the XenServer console since the was never able to connect to the pool master. To resolve this I used the following command:

xe pool-emergency-transition-to-master
This made the XenServer in question the pool master and now I was able to see the network interfaces and set a new IP address. I ran the same command on the other two XenServers as well. Since I now had a situation where the I had multiple pool masters for the same pool I ran the following command on all of the XenServers that were formerly in the same pool:

To get a list of the hosts and uuids of the pool members
xe host-list
To remove the invalid pool members
xe host-forget uuid="xenserver uuid"
When these steps were complete I had then had 4 XenServers in 4 seperate pools. I then used the XenServer console to add the 3 XenServers to the same pool of the original XenServer pool master after properly configuring the IP of the management interface.