Question : Problem: Cisco Router IOS upgrade opinions, please

I am working for a company who has 5 Cisco Routers:

1. IOS (tm) C1700 Software (C1700-SY-M), Version 12.1(5)T9,  RELEASE SOFTWARE (fc1)
2. IOS (tm) C2600 Software (C2600-I-M), Version 12.0(3)T3,  RELEASE SOFTWARE (fc1)
3. IOS (tm) C2600 Software (C2600-I-M), Version 12.2(5d), RELEASE SOFTWARE (fc1)
4. IOS (tm) C2600 Software (C2600-IS-M), Version 12.3(6a), RELEASE SOFTWARE (fc4)
5. IOS (tm) 3700 Software (C3725-IPVOICE-M), Version 12.3(6a), RELEASE SOFTWARE (fc4)


There doesn't seem to be any problems, as of right now, but I was asked to find out which of these IOS's should be upgraded and which, if any, must be upgraded. They are mainly interested in upgrading the IOS, if need be, for security issues, not added features. As of right now they don't have the need for added features.

Does anyone have any opinions of these IOS's, whether they are OK or need to be upgraded? Or, how can I find out from Cisco? I have spent a lot of time on cisco.com trying to find the answer, but man am I confused now!

Thanks!

Answer : Problem: Cisco Router IOS upgrade opinions, please

If it was me, I would upgrade the 1700 and 2600 to the latst release of 12.2, which is somewhere around 12.2.29 or so. Lots of bug fixes and vulnerability fixes also. Those 4 routers are all running very old versions of their own software trains. 12.2 is quite good. It will require more memory and maybe flash than what you have, so check that before upgrading.

The 3725, go to the latest version of 12.3.

12.4 is pretty new, and I wouldn't go there unless you needed something that it offers.