Network Operators and smurf

Doug Stanfield DOUGS at
Mon Apr 27 17:22:06 UTC 1998

Don't assume it's not needed for the 75xx, or anything else for that
matter.  Many networks are single connected to routers that are also
acting multihomed to core providers and these boxes are being used.

Doug Stanfield          		Oceanic Cable            
Data Networking Manager        	200 Akamainui St.
dougs at        	Mililani, HI  96789

	Usially the low-end traffic is symmetrical. The problem is that
CEF code 
	and other anty-frauding realisations are appearing for the
	routers, white they are nessesary for the low-end routers and
useless for 
	the core routers. For cisco, we need this future for
	ASAP, 720x slightly, and don't need it for 75xx at all.

	On Sat, 25 Apr 1998, Al Reuben wrote:

	> Date: Sat, 25 Apr 1998 12:30:50 -0400 (EDT)
	> From: Al Reuben <alex at>
	> To: Havard.Eidnes at
	> Cc: jra at, nanog at
	> Subject: Re: Network Operators and smurf
	> > This should (naturally) be implemented where routing is
	> > and where a "reverse-path check" (looking up the source
address in
	> > the routing table to find the "expected" incoming interface
	> > checking whether the packet did indeed enter through that
	> The big question is, what do you do if most of your traffic
	> asymetrical? I mean, a more basic check could be, "Does the
network that
	> this packet was sourced from exist *at all*?", or "Do I have a
route back
	> to the source network through *any* interface?"
	> That would cut down on a good amount of spoofing, like the
idiots who
	> spoof from etc.

	Aleksei Roudnev, Network Operations Center, Relcom, Moscow
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