Mobile IP

After PPP is connected (and IPCP completed), the PDSN sends an ICMP Router Advertisement message with a Mobility Agent Advertisement extension. This may be solicited or unsolicited, depending on configuration. The mobile then sends a Registration Request message to the foreign agent address in the advertisement. This request includes the address of a home agent or one of the special values 0.0.0.0 or 255.255.255.255. The special values indicate that the mobile has no knowledge of its home agent address and is requesting that the PDSN determine this address (which is in general possible only if the PDSN operator and the HA operator have a prior arrangement). The MOB-IP-SIM simulates the result of sending the mobile's request to a home agent and returns the appropriate response.

In the normal case, the mobile sends a request and receives an acceptance message (code 0). If the mobile's clock is out of sync with the HA's clock, the HA returns code 133 (registration identification mismatch) and the mobile registers using the correct time.

If the mobile attempts to contact a home agent that the MOB-IP-SIM is not set to simulate, or if the HA is set to return no answer, or if the FA is disabled, the mobile will receive no reply. Check the aforementioned things.

If the mobile uses a key other than the one in the MOB-IP-SIM to register, it will receive code 131 (mobile node failed authentication). Ensure that the MN-HA shared secret in the mobile matches the one in the MOB-IP-SIM.

Some mobiles are unable to handle code 136 (unknown home agent address), which is sent as part of HA address discovery. The `Accept dynamic HA request' option causes the simulated HA to send a Registration Accept in this case.

Some mobiles will refuse to accept a registration reply if they believe they are already registered on a network. There will typically be an option under a menu somewhere called `Sign Out' to clear this registration status.