If masterservers are missing from your game client, you may not receive a complete list of all available online game servers.
There has been some discussion about Epic Games possibly providing a new Unreal masterserver, but no confirmation as of yet.
Either way, so long as you update the masterserver list in Unreal.ini with the current community-provided masterservers, there is little to worry about.
Below is a list of our current masterservers (please note that masterserver address "hyper.dnsalias.net" has changed). Players/server admins are encouraged to update their masterserver list in Unreal.ini:
[Engine.GameEngine]
....
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master.oldunreal.com MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master.hlkclan.net MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master2.oldunreal.com MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master.hypercoop.tk MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master.newbiesplayground.net MasterServerPort=27900
ServerActors=IpServer.UdpServerUplink MasterServerAddress=master.qtracker.com MasterServerPort=27900
[UBrowserAll]
...
ListFactories[0]=UBrowser.UBrowserGSpyFact,MasterServerAddress=master.oldunreal.com,MasterServerTCPPort=28900,GameName=unreal
ListFactories[1]=UBrowser.UBrowserGSpyFact,MasterServerAddress=master.hlkclan.net,MasterServerTCPPort=28900,GameName=unreal
ListFactories[2]=UBrowser.UBrowserGSpyFact,MasterServerAddress=master2.oldunreal.com,MasterServerTCPPort=28900,GameName=unreal
ListFactories[3]=UBrowser.UBrowserGSpyFact,MasterServerAddress=master.hypercoop.tk,MasterServerTCPPort=28900,GameName=unreal
ListFactories[4]=UBrowser.UBrowserGSpyFact,MasterServerAddress=master.newbiesplayground.net,MasterServerTCPPort=28900,GameName=unreal
The master server list can have changed since posting. For the most up to date list, please visit the master server guide at the OldUnreal wiki:
http://www.oldunreal.com/wiki/index.php?title=Masterserver_Guide