FYI - Just came across a fairly concise, interesting article about firewalls in a routed network environment. It explains basic routing, ARP, ARP on subnets, proxy ARP, and some dynamic routing across firewalls ideas. One graphic seems to be missing in the second article and I''m not sure I''d endorse all the opinions, but it''s a useful starting point. The two-part article was apparently produced for a WatchGuard newsletter, but is reprinted by a consultancy called Core Competence at: http://www.corecom.com/external/livesecurity/routing1.htm http://www.corecom.com/external/livesecurity/routing2.htm If you are short on reading material, they have several other security-related white papers at http://www.corecom.com. Ron