SRST - for phones and other similar devices that support SRST to register with the router when CCM is not available.
MGCP Fallback (not SRST!) - This is where the MGCP configured voice ports fallback to H.323 mode (IOS/default application) when the router MGCP and ccm-manager functions can not establish connection to call-manager AND ccm-manager is configured for fallback-mgcp.
Depending on the outage type, when the router MGCP and ccm-manager can't speak to CCM they will be in fallback mode (H.323) and the ccm-manager and MGCP will continously check to see if the server is available, just like phones in SRST mode. When a phone in SRST is able to re-register to a call manager it does automatically and goes out of SRST mode.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...