====== MGCP Fallback ======
  * Provide gateway functionality to IP Phones in SRST mode
  * Might be used as a standalone feature to provide analog phones locally attached to a Cisco IOS router with survivability
  * Most often used with SRST
  * MGCP fallback to its default call-control application (H.323 or SIP)
  * PSTN Call Preservation
    * Preserve for Analog or CAS call
    * No call preservation for ISDN PRI or BRI because of q.932 backhaul
    * Preserve in fall back to MGCP
  * This is really SRST (a Cisco term) but the industrial term is MGCP Fallback
{{cucm-mgcp9.png|}}

**Fallback**
  * Immediate - after a preconfigured time
  * Graceful - after all the open connections are closed
{{cucm-mgcp-fb1.png|}}

===== Configuration =====

==== CUCM SRST Reference ====
  * Under **System > SRST**
  * Create SRST reference
{{cucm-mgcp-fb2.png|}}

==== CUCM Device Pool ====
  * Under **System > Device Pool**
  * Assign SRST reference to device pool of phone
{{cucm-mgcp-fb3.png|}}

==== Router SRST ====
  * Configure [[cucm-srst|Router SRST]]

==== Router MGCP Fallback ====
  * Enable MGCP fallback
<code>
ccm-manager fallback-mgcp
</code>

  * Specifies that the voice application named Default takes over if the MGCP call agent is not available; this allows a fallback to H.323 ro SIP
<code>
call application alternate default
</code>
  * Or
<code>
application
  global 
    service alternate Default
</code>