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L2TP and Graceful Routing Engine Switchover
Graceful Routing Engine switchover (GRES) is supported on MX Series routers acting as either the L2TP LAC or LNS. In the event that L2TP (the l2tp-universal-edge process) restarts or that the router fails over from the active routing engine (RE) to the standby RE, L2TP graceful Routing Engine switchover ensures that the following occurs:
- The LAC and the LNS recover destinations, tunnels, and sessions that were already established at the time of the failure or restart.
- The LAC and the LNS respond to tunnel keepalive requests received during the switchover for established tunnels, but do not generate any keepalives until the switchover is complete.
- The LAC and the LNS delete all the tunnels and sessions that are not in the Established state.
- The LAC and the LNS reject requests to create new tunnels and sessions.
- The LAC and the LNS send another disconnect notification to the peer for sessions and tunnels that are already in the Disconnecting state at the time of the failure or restart. For sessions and tunnels that were coming up at that time, the LAC and LNS send a disconnect notification to the peer.
- The LAC and the LNS restart timers for the full timeout period for recovered L2TP destinations, tunnels, and sessions.
 | Note: Graceful Routing Engine switchover is supported only by L2TP LAC and LNS on MX Series routers. It is not supported by L2TP LNS on M Series routers. |
