Gary,
I know there are some software soltutions that will let you type in an IP address and it'll tell you what port its connected to in your infrastructure.
Look at Solarwinds I think one of there suites has this ability. I can't think of the other one.
If you type into google "ip address switchport mapper" you'll get a bunch of hits.
Here is one of those hits.
http://www.netscantools.com/spmapmain.html
Patrick
HTH please rate any posts that are useful.