Supported Platforms
Related Documentation
Mobile IP Routing and Forwarding
Mobile IP employs a care-of address to process traffic for the mobile node.
The mobile node acquires the a care-of address from the foreign agent. The care-of address is reachable from the mobile node, and routable from the home agent. The mobile node includes the care-of address in its registration request to the home agent. After AAA or local authentication successfully processes and authenticates the RRQ and provides both the authorization parameters for the mobile node and an IP address, the home agent then sets up the data path for the mobile node and sends back a registration reply (RRP) confirming successful registration of the mobile node.
When the foreign agent receives the successful RRP from the home agent, the foreign agent sets up the data path for the mobile node. Then it sends the RRP to the mobile node to acknowledge that the mobile node is now successfully registered and the data path between the home agent and the mobile node is in place.
The home agent supports generic routing encapsulation (GRE) and IP-in-IP tunnel encapsulation for forward and reverse tunneling. The tunnels must be statically configured. When packets destined for the mobile node reach a home agent, the home agent encapsulates the packets and tunnels them to the care-of address. Packets that exceed the maximum transmission unit (MTU) value of the tunnel are dropped and an ICMP error message is sent to the source IP address. Packets without an access route are returned to the source with an ICMP destination unreachable error message. For reverse tunnels, packets are de-tunneled and forwarded towards the next hop to the destination address.
Mobile IP does not support graceful Routing Engine switchover (GRES). It handles the rebooting of processes in the following ways:
- Mobile IP process—After Mobile IP completes a restart, it removes the Mobile IP subscriber entries from AAA and the session database. When that is complete, Mobile IP can process new mobile node registration requests.
- AAA process—After AAA completes a restart, Mobile IP removes all subscriber data held internally by AAA and all corresponding session database entries.
- Routing protocol process—When the connection between the routing protocol process and Mobile IP is lost, Mobile IP responds by clearing the mobile node bindings that are associated with the logical system in which the routing protocol process restarted. The routing protocol process maintains routes to mobile nodes during the restart. The routing protocol process flushes these routes if they are not reinstalled after the restart completes and before the stale route timer expires.
