Have a customer with a number of Cisco 2821 routers running Adv. Ip. Services, 12.4(11)XW7 with Frame-Relay links, H323 gateways, PRI, Voip with Call Manager 6.x,Unity, IPCC. Customer wants to know whether they should upgrade the 2821's to 12.4(20)T5 or 12.4(23)T3, both the latest. Not looking for any new features, just stable reliable code. Tried Cisco IOS on-line upgrade tool. Doesn't seem to be to helpful. Any suggestions would be appreciated?
Thanks in advance,