Two survivable core servers are administered and the LSP in the S8300 is administered last in the secondary list in gateways 1 and 2. When the branch becomes isolated the gateways cannot connect to the primary server or the secondary core servers and therefore connect to the last server in the list, the S8300 in the same branch, see Figure 8: Survivable remote server working in a survivable core server environment - normal operation.

The gateway has a Primary Search Timer, which is used when attempting to contact the main server. If the gateway loses its registration with the main server, it will attempt to re-register with the main server for that time. The default value is one minute but it can be administered to be as high as 30 minutes. If registration to main server is unsuccessful, the gateway will attempt to register with a server in the backup server portion of the Media Gateway Controller (MGC) list. The gateway will try each server in turn and, if there are no responses from any of the servers, gateway will go to the top of the MGC list and try each server in turn until a server responds.

The problem that caused the outage has been fixed (see Figure 10: Survivable remote working in a survivable core environment - fall-back to the main server).

If a media gateway recovery rule has been assigned, the media gateway will register with the main server when the recovery rules parameters have been met. If a recovery rule has not been assigned or if you want the gateway to immediately return, run the enable mg-return command. A manual reset of the gateway or the survivable remote server is not required.