Where can I ask questions for networking?
Is there any Stack Exchange site for Cisco CCNA/CCNP/CCIE and Juniper Networks professionals?
That is, for people who configure and support ISP grade WAN, MAN and Corporate Networks.
Sometimes it isn't quite as clean as Al suggested... You may wind up dividing your questions between implementation (on Server Fault) and theoretical (Stack Overflow)...
Seems like Server Fault
The on-topic place for applied networking questions is Server Fault.
And yes, you're right, there's very little cross-over between installing Microsoft Exchange Server and configuring a carrier-grade switch... but you have to draw the line somewhere otherwise you end up with HP-Procurve-exchange, juniper-exchange, extreme-networks-exchange, Cisco-routers-but-not-the-3900/2900/1900-range-because-they-suck-exchange, exchange2003-exchange, sendmail-exchange, c++-exchange, c#-exchange and so on.
And no chance of ever finding the right place to ask your question among all the flame wars about whether or not a new Cisco IOS revision or Exchange Server service pack or .NET version that changes C# around a bit warrants a new Stack Exchange site or not.