Can we make outgoing phone calls in SRST mode with out configuring MGCP fall back?

[Yenosh]

Hi 

I am confused about these concepts , can anyone please explain

Can we make outgoing phone calls in SRST mode with out configuring MGCP fall back?

Is Call preservation works in SRST mode without MGCP fall back?

[Nithin Eluvathingal · Accepted solution]

MGCP gateway fallback preserves active calls from remote-site IP Phones to the PSTN when analog or CAS protocols are used. For ISDN protocols, call preservation is impossible because Layer 3 of the ISDN stack is disconnected from the MGCP call agent and is restarted on the local Cisco IOS gateway. This means that for active ISDN calls, all call-state information is lost in cases of switchover to fallback operation.

CUCME in SRST mode enables routers to provide basic call-handling support for Cisco Unified IP Phones if they lose connection to remote primary, secondary, and tertiary CUCM installations or if the WAN connection is down.

MGCP gateway fallback,  is a feature that improves the reliability of MGCP remote site networks.