[52742] in North American Network Operators' Group
Re: Who does source address validation? (was Re: what's that smel
daemon@ATHENA.MIT.EDU (Steve Francis)
Thu Oct 10 01:42:58 2002
Date: Wed, 09 Oct 2002 22:43:50 -0700
From: Steve Francis <steve@expertcity.com>
To: Valdis.Kletnieks@vt.edu
Cc: nanog@merit.edu
Errors-To: owner-nanog-outgoing@merit.edu
Valdis.Kletnieks@vt.edu wrote:
>
> My personal pet peeve is the opposite - we'll try to use pMTU, some
> provider
> along the way sees fit to run it through a tunnel, so the MTU there is
> 1460
> instead of 1500 - and the chuckleheads number the tunnel endpoints out
> of
> 1918 space - so the 'ICMP Frag Needed' gets tossed at our border
> routers,
> because we do both ingress and egress filtering.
That's not terribly hard to overcome - allow icmp unreachables (from any
source) in your acl, then deny all traffic from RFC 1918 addresses,
then the rest of the ACL.
Combined with CAR (or CatOS QoS rate limiting) on icmp's, you end up
with all the functionality, and almost none of the bogus traffic.
