Subject: [Mip4] ARP with MIPv4

From: [email-masked]
Date: Tue, 20 Sep 2005 11:02:35 +0200

Hi all,

can someone please explain why a MN is not allowed to send an ARP
Request containing its HoA on a foreign link? Let's assume that another
host then adds an entry (MN HoA,MN L2@) into its ARP cache. This entry
would only be used if the MN's HoA is reachable via one of the host's
direct links. That would entail that the host is attached to the MN's
home network. But in that case the IP packet would be intercepted by the
HA which would tunnel it to the MN's CoA. So everything's just fine. Or
am I missing something?

Kind regards,

Rajendra

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From: Alexandru Petrescu <[email-masked]>
Date: Tue, 20 Sep 2005 12:25:28 +0200

[email-masked] wrote:
> Request containing its HoA on a foreign link?

I think in the case of FA CoA mode, the only way for MN to talk to FA is
 for MN to use its HoA on the foreign link, which means MN does use ARP
with respect to its HoA, and on the foreign link.

However, I think it is not good that after this ARP exchange the FA ends
up with a route pointing to the HoA, because that same route is also
present at HA (or at the home border router).  I think it is technically
unsound to have two different routes towards same IP address indicating
two _different_ physical locations (two different routes towards same IP
address at _same_ physical location is fine).

There may be a risk of propagation of the route at the FA that points to
the HoA.

There may be a risk of address collision when two Mobile Nodes of
different HAs have the same home address from the private space
(10.x.x.x) and visit the same FA.

But things seem to work out fine: FA is forbidden from using broadcast
ARP, MN HoAs are not behind NAT, FAs use Visitor Lists, etc.

> Let's assume that another host then adds an entry (MN HoA,MN L2@) 
> into its ARP cache. This entry would only be used if the MN's HoA is 
> reachable via one of the host's direct links. That would entail that 
> the host is attached to the MN's home network.

But the MN is not at home, right?, MN is on the foreign.  I don't
understand...

Alex

> But in that case the IP packet would be intercepted by the HA which
> would tunnel it to the MN's CoA. So everything's just fine. Or am I
> missing something?
> 
> Kind regards,
> 
> Rajendra
>