I recently completed a set of modifications to the default configs in 12.09 Attitude Adjustment to allow for a multi-interfaced LAN setup. By default, the configuration system only likes one LAN segment, whereas I wanted two - LAN (wired) and WIFI. My hacks cover:

- how to run one copy of dropbear on several interfaces
- how to provide interface-dependent DHCP
- how to provide interface-dependent DNS

Please find the two part write up here:
Part1 - dropbear
Part2 - dnsmasq