Subject: [mobile-ip] MIPv4: can a foreign agent broadcast an ARP request for the home address of a mobile node?

From: Bekiares Tyrone-CTB041 <[email-masked]>
Date: Wed, 2 Jan 2002 11:34:19 -0600

I've been reading over the MIPv4 RFC-2002 and the updated Internet Draft in greater detail, and it appears to be somewhat ambigious as to whether or not a foreign agent can broadcast an ARP request for the home address of a mobile node.

Page 59 of the updated Internet Draft "IP Mobility Support for IPv4, revised" states that "A Foreign agent MUST NOT use broadcast ARP for a mobile node's MAC address on a foreign network." Yet on page 66 of the same draft, it reads "Finally, while the mobile node is away from home, it MUST NOT reply to ARP Requests in which the target IP address is its own home address, **** unless the ARP Request is unicast by a foreign agent with which the mobile node is attempting to register or a foreign agent with which the mobile node has an unexpired registration ****"

That last bit seems to imply the use of a unicast ARP request mechanism, which dosen't make any sense to me (anyone?). The original RFC basically has the same verbiage, but leaves out the word "unicast"...

Why would the FA ever need to do an ARP request for the the mobile node's home address? Shouldn't it update its ARP cache based on the MIPv4 Registration Request (discussed on page 59 of the Internet Draft)?

Thanks!

+ Tyrone Bekiares
- Advanced Technology, Motorola