My master server has changed IP's. I moved it from the Amazon cloud to the Azure cloud.
Most existing configurations will update automatically. For a month or so my old server will work so there is no rush.
We've lost one of the community masters - the "seattle" master server hasn't responded in many months.
I've updated the "for servers" info in
http://ns2.pu.net/unofficial.zip
ditto "for clients" info in
http://ns2.pu.net/ServerPrefs.cs.zip
you would need one of these two files if you were setting up a new server or setting up a new client.
PS:
there is a server in provo utah called "Fun House" which has a firewall that is too tight. It is only allowing the old master server to query it. if this is your server you need to allow traffic from anywhere to get to your port 28001 so that anybody can see your server.