CIPTV2 – How to setup SRST with MGCP Fallback – Part 1

Ok so here is how it is done… to a basic level..

1. Add the SRST Reference to CUCM and apply to the Device Pool

2. Logon to the IOS Gateway

If the endpoints are SCCP:

ip source-address (CUCM SUB IP)
max-dn 1 dual-line
max-ephones 1

If they are SIP:


3. Enable MGCP Fallback on IOS Gateway

ccm-manager fallback-mgcp
service alternate Default


Pull the WAN Link!


Check the endpoint and it should state it is in CM Fallback Service Operating blah blah…

Ok good…

Now check that the IOS Gateway is in Fallback Mode:

BR2#sh ccm-manager fallback-mgcp
Current active Call Manager:    None
MGCP Fallback mode:             Enabled/ON
Last MGCP Fallback start time:  20:14:48 UTC Jan 27 2016
Last MGCP Fallback end time:    20:12:15 UTC Jan 27 2016
also your ISDN should be up!
BR2#sh ip int br | inc 15
Serial0/0/0:15             unassigned      YES NVRAM  up                    up


If you enable a debug on the IOS Gateway you will see the phone actually register to the Gateway:

‘debug voice register events’

*Jan 27 20:14:25.315: %IPPHONE-6-REGISTER_NEW: ephone-1:SEP001BD47D22EB IP: Socket:1 DeviceType:Phone has registered.


Good stuff and that is a basic SRST with MGCP Fallback configuration. Phone is registered and the ISDN is up!

However there are few more pieces to the puzzle to follow on the next post…