Cisco Unified SRST and MGCP Fallback
This section reviews the configuration of SRST to provide call survivability and MOH for SCCP phones and MGCP fallback for gateway survivability.
Overview
Activate and configure the MGCP-gateway-fallback feature on the Cisco IOS router. Configure Cisco Unified SRST on the side of the CUCM and on the side of the Cisco IOS router.
Configuration
Follow these steps for configuration:
- Step 1. Define the SRST references for phones on the CUCM. The default TCP port is 2000 for SCCP and 5060 for SIP.
Step 2. MGCP fallback and Cisco Unified SRST are enabled and configured on the IOS gateway; use the call-manager-fall-back command.
Following is a sample configuration:
R1# configure terminal R1(config)# call-manager-fallback R1(config-cm-fallback)# ip source-address 10.10.20.1 port 2000 R1(config-cm-fallback)# max-ephones 3 dual-line R1(config-cm-fallback)# max-dn 6 R1(config-cm-fallback)# limit-dn 7960 2 R1(config-cm-fallback)# keepalive 25 R1(config-cm-fallback)# end
Following is a sample MGCP-gateway-fallback configuration for an SRST-enabled Cisco IOS router:
R1# configure terminal R1(config)# ccm-manager fallback-mgcp R1(config)# application R1(config-app)# global R1(config-app-global)# service alternate Default R1(config-app-global)# end R1#
- Step 3. Use an additional command for call preservation when using MGCP fallback:
voice service voip h323 no h225 timeout keepalive
- Step 4. Configure the CFUR feature on the CUCM to reach remote sites in SRST mode. Also, configure the Max Forward Unregistered Hops to DN option in the Service Parameters. A reasonable setting of 2 for this option can eliminate routing loops.
- Step 5. Implement a simplified dial plan on the remote-site gateways to provide proper calling privileges and dialing behavior by using dial-peers and voice translation profiles.
