So my (Debian based) firewall routes traffic for the three subnets I have behind it, each which is front-ended by either a Cisco 851 or a Linksys AP.
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The first scanner (on my Son's Ubuntu 7.10 Optiplex) scans the non-Linksys devices connected to the AP, both wired and wireless. (I exclude the traffic because even traffic through the APs hangs the WRT54G and sometimes the WET54G (bridge). The second scans its local subnet and the other Cisco-protected subnet. I will add a third Nessus scanner behind this subnet that scans back so that on the non-Linksys segments I have a perspective of scans both inside and outside the Firewall (meaning router ACLs)