It depends on the network. Usually, irc.network will give you a random server; as Merlin said, though, currently DALnet has this disabled and you'll get the "Can't assign address" error if you tried to get to irc.dal.net. You might let mIRC itself use its server list and try to use something like this:
Code:

alias StartUp.Connect {
  server DALnet 7000 -i Nick1 Nick2 -j #mIRC,#HelpDesk
  server -m EFnet 6667 -i Nick3 Nick4 -j #mIRC
  server -m Quakenet 6667 -i Nick5 Nick6 -j #mIRC,#Help
}


DALnet: #HelpDesk and #m[color:#FF0000]IR[color:#EEEE00]C