Blocking spoofing at the source (was: ICMP Attacks??)

Josh Beck jbeck at
Fri Aug 22 21:59:40 UTC 1997

> > Given the predominance of Ascend in the marketplace, and their general
> > configuration style, it would be cool to see an option
> > "AllowIpSpoofing=Yes/No" or the like. The boxes already carry routes
> > associated with each interface. If a packet arrives that doesn't have a
> > route to get it back to the interface it came from, it would be dropped.
> > Sure, this may not always be what you want, but in 99% of the cases it
> > would be. Implementation via Radius would permit this to be removed from
> > people you wish to allow to spoof. :)
> This won't work on anything with multiple diverse paths. And I don't know
> many companies with their own WANs that don't have such.
> So, yes, the idea is nice but the logic would have to be much more
> comprehensive than that. And I honestly don't know how you could safely do
> it, that won't break half the routing topologies out there.
> (if you assume multipath OSPF for the IGP... maybe. But that's one hell of
> an assumption.)
> -- 
> Joe Rhett                                                 Systems Engineer
> JRhett at ISite.Net                                          ISite Services
> PGP keys and contact information:

	True, but there are a lot of small ISPs whom something like this
could help. Granted, perhaps you should know enough of filters and routes
to run an ISP, but there are those who don't, and their numbers will only
increase as the involved equipment and technologies become more accessible
to more people, and more PC shops and small businesses decide to become
their own ISPs.

Josh Beck                                         jbeck at
CONNECTNet INS, Inc.      Phone: (619)450-0254      Fax: (619)450-3216
6370 Lusk Blvd., Suite F-208                       San Diego, CA 92121

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