First let me apologize, for I don't know if this is the right section for this, but wasn't sure where else to put it.
I recently was able to get a few 2501 routers with IOS 9.14 and one 2507 with IOS 12.1 to practice for my CCNA. Everything is going well except for problems I am having with RIP and IGRP.
On the 2507 I setup the proper subnets/IPs on int s1. Then I setup IGRP with an AS of 1, and the networks. I moved to my first 2501 and started setting it up with out a problem on int s0. Int s1 goes to my next 2501. IGRP/Subnets/IPs were all setup. On the last 2501 I finalized the setup. I used HDLC as the encap for all the connections between routers. Now however I am getting a "suppressing null update." I also noticed that the protocol between the two 2501 routers goes down after a short time. I have triple checked the encap, making sure it's hdlc so I am at a loss of what to do.
I'm not sure what could be causing this. Any help would be greatly appriciated.