I've always used Dia or Visio to make mine with.
Basically you just make a link for every relevent connection
or protocol. So you would have different links for say IP, VPN,
and/or routing protocols (RIP, OSPF, BGP, etc...). As long as
everything is "clear", it should be fine. A lot of what is standard
is based on what is included protocol/connection wise in the network.
I hope this helps,