T3 or not to T3

Avi Freedman freedman at netaxs.com
Mon Jul 22 17:51:41 UTC 1996

> > Yeah, definately.  But most backbones seem to have "customer routes" as
> > an option, and if I trust them enough to get those routes correct then
> > I will hopefully not have to bother with extreme amounts of filtering.
> > It's pretty easy to enforce "no transit" at the packet filtering level
> > -- only packets destined for my nets will be allowed in.  Is there some
> > other aspect of filtering I'm forgetting about?  We have a dedicated
> > and backup network engineer at any rate.  The border router would be a
> > cisco 7200 or 7500 series with 128Mb.
> > 
> > Dean
> Is this really how people enforce "no transit"? I have been told that packet
> filtering is quite cpu expensive. I would think that packet filtering on a 
> router that is probably already overburdened is not an attractive solution.
> Jim

I'm not sure if this is how people enforce it; you're correct that it's
pretty expensive to do it this way.

We run a periodic script that sends 8-10 pings for various destinations,
including non-existent ones, into exchange-point neighbors to see where 
the packets go.

If packets for nowhere IPs come back at you, they're defaulting into you...


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