Using NAT for best-exit routing

Jeff Mayzurk jeffm at
Fri Aug 28 17:53:28 UTC 1998

Brian Dickson wrote:

> such peer networks). Ingress traffic to the web farm provider has it's
> *source* address NAT'd, and internal routing points return traffic to
> the *same* NAT through which the request traffic came.
> Thus, return (data) traffic is best-exit.

> Side benefits are that the unique address pools allow for much easier
> per-peer and per-region collection of stats, eg netflow (at some place
> other than NATs).

As you point out, stats collection is easier--but only from a network ops 
point of view, and even then, only if you're simply concerned with symmetric 
flow of traffic to your upstreams/peers. 

However, your web server logs are now useless, because all the requests come 
from a static pool of local addresses. If you're a big web farm like Exodus, 
your customers aren't going to buy this.


Jeff Mayzurk
Manager, Systems/Network Engineering   <jeffm at>
E! Online 
150 Chestnut Street                    415.772.3555 x4496
San Francisco, CA  94111               415.984.0322 FAX

More information about the NANOG mailing list