Unexpected Termination of L2TP Tunnels after Unified ISSU

On an E120 or E320 router serving as an LNS in an environment having L2TP tunnels more than 16,000, L2TP tunnels established over ES2 10G UPLINK LM, ES2 10G LM, and ES2 10G ADV LM modules are terminated after unified ISSU. The ISSU reload phase for the ES2 10G UPLINK LM, ES2 10G LM, and ES2 10G ADV LM modules is greater than 80 seconds, which causes the L2TP hello packets to be lost and therefore the L2TP tunnels to be terminated.

To avoid unexpected L2TP tunnel termination, you can use the l2tp fastpath-hello-processing command in the LNS for enabling the handling of L2TP hello packets in fast path during unified ISSU. For more information about the handling of hello packets in fast path, see Controlling the Handling of L2TP Hello Packets in Fast Path.

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