[nsp] RPF problem with ICMP unreachables

[Gert Doering]

Hi,

On Sun, Nov 24, 2002 at 03:55:46PM +0200, Hank Nussbacher wrote:
> How does one force a router to not use *highest* IP address to return ICMP 
> unreachables and instead use the interface from where the ICMP came?

I've observed differences in Cisco and Juniper here if routing is
asymmetric.

Cisco seems to reliably reply with the address of the interface that the
original came in.

Juniper uses the IP address of the *outgoing* interface as the source
address of the ICMP packet.

Both approaches are "correct", I personally find Cisco's more useful
(because the output from Juniper is highly confusing on traceroute'ing
through asymmetrically routed networks).

None of this can explain *your* problem, though, as both types should
use the interface pointing towards your router...

gert

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Gert Doering - Munich, Germany                             gert@greenie.muc.de
fax: +49-89-35655025                        gert.doering@physik.tu-muenchen.de