I apologize, it was EIGRP I was concerned about. I ran the show ip eigrp topology and traffic command on three routers. The models are two 2620's, and one 3660. Here are my results.
2620's both get a very long list of eigrp topology. They also show lots of eigrp hellos. The eigrp updates, queries, replies, and acks are in the thousands.
The 3660 only has about 5 items (passive) on its eigrp topology list and the same amounts of eigrp hellos at the 2620's. However, it shows zero updates, queries, replies, and ACKs.
Version Numbers of IOSes
1.) 2620 - 12.0(5)T1
2.) 2620 - 12.0(3)T3
3.) 3660 - 12.0(7)T
Any ideas?