Configuring IP Reassembly

You can enable IP reassembly on a virtual router basis. Also, on a systemwide basis, you can control how the router handles verification of sequence numbers in data packets that it receives on L2TP tunnels.

ip tunnel reassembly

Use to enable the reassembly of fragmented IP tunnel packets that are received on the current virtual router.
You configure tunnel reassembly on VPN routing and forwarding routers independent of the tunnel reassembly configuration on the parent virtual router.
Example—Enables reassembly for virtual router vr12 and disables reassembly for virtual router vr8
host1:vr12(config)#ip tunnel reassembly host1:vr12(config)#virtual-router vr8 host1:vr8(config)#no ip tunnel reassembly
Use the no version to return IP tunnel reassembly to the default, disabled.
See ip tunnel reassembly.

l2tp ignore-receive-data-sequencing

Use to prevent sequence number verification for data packets received on all L2TP tunnels in the router. This command does not affect the insertion of sequence numbers in packets sent from the router.
If you are using IP reassembly, we recommend that you set up the router to ignore sequence numbers in received data packets. Because IP reassembly can reorder L2TP packets, out-of-order packets can be dropped if sequence numbers are being used on L2TP data packets.
Example
host1(config)#l2tp ignore-receive-data-sequencing
Use the no version to cause the router to verify sequence numbers on received L2TP data packets.
See l2tp ignore-receive-data-sequencing.