I’ve spent a few hours this evening getting back to basics, and taking the time to review what I’m going to call ‘Minimum Require Configuration’ for SRST – both SIP and SCCP.
SCCP SRST Minimum Required Configuration
ip source-address 10.10.210.28 port 2000
SIP SRST Minimum Required Configuration
voice service voip
registrar-server expires max 600 min 60
voice register global
voice register pool 1
id network 10.10.210.0 mask 255.255.255.0
With the configuration shown, both SIP and SCCP devices can failover to the Cisco 28xx ISR that I’m using for testing. There are lots of other nerd knobs you can tweak if you want, but this is all that’s required to get endpoints to register.