Managing Address Changes Received from Remote Endpoints

A remote endpoint can use the Start-Control-Connection-Reply (SCCRP) packets that it sends to the E-series LAC to change the address that the LAC uses to communicate with the endpoint. By default, the LAC accepts the change and uses the new address to communicate with the endpoint. However, you can configure the LAC to ignore or reject the requested change. Setting up the LAC to ignore address changes in SCCRP packets enables the router to construct tunnels with separate receive and transmit addresses and to avoid problems due to a misconfiguration. Three possible configurations are available:

• Default configuration—The E-series LAC accepts the change from the endpoint. The LAC then sends all subsequent packets to, and accepts packets from, the new address.
• Ignore configuration (specified by the l2tp ignore-transmit-address-change command)—The LAC continues to send packets to the original address but accepts packets from the new address.

  host1(config)#l2tp ignore-transmit-address-change

  Use the ip-address or udp-port keyword to ignore the specific address component. Omit the keywords to ignore the entire address change in the SCCRP packet.

• Reject configuration (specified by the l2tp reject-transmit-address-change command)—The LAC sends a Stop-Control-Connection-Notification (StopCCN) to the original address, then terminates the connection to the endpoint.

  host1(config)#l2tp reject-transmit-address-change ip-address

  Use the ip-address or udp-port keyword to reject the specific address component. Omit the keywords to reject the entire address change in the SCCRP packet.

The reject specification takes precedence over the ignore specification.

The router accepts a change in receive address only once, during the tunnel establishment phase, and only on an SCCRP packet. Subsequent changes result in the router dropping packets. Any changes do not affect established tunnels.

Use the show l2tp command to display the SCCRP address change configuration.

Related Topics

• l2tp ignore-transmit-address-change command
• l2tp reject-transmit-address-change command

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