From: ccie2be (ccie2be@nyc.rr.com)
Date: Sat May 28 2005 - 14:21:07 GMT-3
Sorry, Steve, I don't understand what you mean by "its usual ip address".
But, extrapolating from what I now know about MN and mobile ip, I have 2
theories about why IRDP isn't needed on the HA both of which could very well
be wrong but here goes...
1. When a MN returns to its home network, it will stop hearing IRDP
advertisements from a FA. So, it will assume it's on another foreign network
and solicit this info on its home network. But, because the MN is back on
its home network, this RRQ goes t the HA instead of another FA. When (and
if) the HA responds to these solicitations, the MN will know (from the
source ip addr of the HA response maybe???) that it's now back on its home
network.
2. Somehow thru the arp process???
3. By default, if the MN doesn't hear any IRDP messages from a FA, it arp's
for its default gateway???
These are all just guesses but they seem plausible.
What do you think?
Tim
-----Original Message-----
From: Stephen Fisher [mailto:stephentfisher@yahoo.com]
Sent: Saturday, May 28, 2005 12:44 PM
To: ccie2be
Cc: ccielab@groupstudy.com
Subject: Re: Mobile IP and IRDP
On Fri, May 27, 2005 at 04:40:04PM -0400, ccie2be wrote:
> Now, it makes sense to me that IRDP needs to be configured on the FA
> router. It also seems to me that IRDP should also be configured on the
> HA interfaces where MN exist so that MN's know they are on the Home
> Network.
>
> But, in the examples on the Doc-CD and in the Cisco Press, IRDP isn't
> configured on the HA.
>
> Do you know why that is?
That's a good question.. the way I understand it, the MN knows it is on
its home network when its assigned address (such as through DHCP)
matches its usual IP address. The Cisco Press Mobile IP book also
mentions comparing its usual address to the prefixes received in IRDP
announcements so now I'm not sure either.
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