In Cisco Unified Communications Manager (CUCM), Media Gateway Control Protocol (MGCP) fallback is a feature that allows organizations to ensure continuous call processing when the primary call control server is unavailable. However, in some scenarios, MGCP fallback may not be required when using Survivable Remote Site Telephony (SRST) configuration. In this article, we will discuss the situations where MGCP fallback may not be necessary with SRST configuration.
SRST is a Cisco technology that provides call processing redundancy for IP phones at remote sites in the event of a WAN outage or other connectivity issue. When an IP phone loses connectivity to the primary call control server, SRST allows the phone to continue making and receiving calls using the local router as a backup call control server. During this time, the router uses a configuration file to maintain basic call processing functionality for the phones at the remote site.
MGCP fallback, on the other hand, is used to ensure that gateways can still operate and maintain their voice services in the event of a CUCM outage. In an MGCP fallback configuration, the router takes over call control for the gateway and ensures that the voice services provided by the gateway continue to function. This is achieved by using a backup configuration file stored on the router.
While MGCP fallback is often used in conjunction with SRST, there are some scenarios where it may not be necessary. One such scenario is when the gateway is not directly connected to the CUCM. In this case, the gateway is configured to use H.323 or Session Initiation Protocol (SIP) to communicate with the CUCM. Since MGCP is not being used, MGCP fallback is not required in this scenario.
Another scenario where MGCP fallback may not be necessary with SRST is when the gateway is being used for voice services other than PSTN connectivity. For example, if the gateway is being used to connect to a third-party voice system, MGCP fallback may not be necessary as the voice system can still operate independently of the CUCM.
In summary, MGCP fallback is a feature that is commonly used in conjunction with SRST to provide call processing redundancy in the event of a CUCM outage. However, in some scenarios where the gateway is not directly connected to the CUCM or is being used for voice services other than PSTN connectivity, MGCP fallback may not be necessary with SRST configuration. It is important to evaluate the specific requirements of the network and gateway when determining whether MGCP fallback is necessary.