[c-nsp] ip load-sharing per-packet and RPF

Gert Doering gert at greenie.muc.de
Tue Oct 12 16:56:50 EDT 2004


On Tue, Oct 12, 2004 at 10:32:37AM -0400, Marr, Joe wrote:
> Is it possible to run "ip load-sharing per-packet" and "ip verify
> unicast reverse-path" on the same interfaces?

Yes (done that on 128 kbit ISDN lines towards customers - BRIx/y:1 and

> I have 2 T1s that are load-balanced with my provider using "ip
> load-sharing per-packet". When I set "ip verify unicast reverse-path" I
> begin to lose every other packet. I had thought Unicast RPF was
> compatible with CEF's per-packet and per-destination load sharing.

I've never done it on links towards "the Internet".  This might cause
problems if both links are not configured fully identically (like
"BGP to two different provider POPs, and non-symmetric routing").

For static routing (two static default routes, nothing else) it *should*

I don't see the major gain here, though.  In that scenario, anti-spoofing
ACL rules are fairly easy to set up, and with dual T1s, even lower-end
routes can do the ACLing in line speed.


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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de

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