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Policy Routing

  • From: Jeff Cates
  • Date: Sun Aug 26 00:34:21 2001


I am a network engineer at a regional southeast USA
NSP. I am looking for some recommendations concerning
a scenario that has been presented to me.

My company is attempting to obtain company X's
Internet transit traffic, which will be  BGP-4 peering
over either a T-3 or OC-3. Due to financial reasons,
my upper management has proposed that I route company
X's Internet traffic via a specific NSP that we peer
with, we'll call them NSP-A. Apparently, NSP-A has a
substantially cheaper rate than our other upstrem
providers and it is anticipated that this customer
will be sending a full T3 or OC-3's worth of traffic
to us.

Redirecting inbound traffic to company X via NSP-A can
be accomplished very easily through use of AS path
prepending, however, coming up with a solution for
egress traffic from company X to NSP-A, via our AS,
has proven a bit more challenging :-).

The only feasible solution that I've been able to come
up with is to stick customer X directly on the router
that peers with NSP-A and employ the use of policy
routing, which would enable me to set the next hop for
company X's traffic to the peering address on NSP-A.

Our NSP-A peering router is a Cisco 12016, running IOS
12.0(16)S2 and it has 256MB of DRAM. 

Additionally, it is configured with NetFlow and dCEF

I've never employed policy routing in this type of
environment and I am concerned about the overhead that
it might place on the router or on the traffic
traversing the interface.

I've also thought about MPLS TE, however, our core
backbone does not run MPLS and even if we did, I
believe I would still have to policy route the traffic
to NSP-A once the MPLS label was popped off the last
router in the path in transit to the NSP-A peering

Any ideas or comments would be greatly appreciated.

Thanks in advance,


[email protected]

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