different flavours of uRPF [RE: register.com down sev0?]
pekkas at netcore.fi
Fri Oct 27 06:50:09 UTC 2006
On Thu, 26 Oct 2006, Tony Li wrote:
> > It was possible to implement BCP38 before the router vendors
> > came up with uRPF.
> Further, uRPF is frequently a very inefficient means of implementing BCP
> 38. Consider that you're going to either compare the source address
> against a table of 200,000 routes or against a handful of prefixes that
> you've statically configured in an ACL.
Isn't that only a problem if you want to run a loose mode uRPF?
Given that loose mode uRPF isn't very useful in most places where
you'd like to do ingress filtering, this doesn't seem like a big
BTW, I still keep wondering why Cisco hasn't implemented something
like Juniper's feasible-path strict uRPF. Works quite well with
multihomed and asymmetric routing as well -- no need to fiddle with
communities, BGP weights etc. to ensure symmetry.
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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