Firewall/NAT

Hi,

Currently i have a soekris box with 3 eth0 and im very happy with it.

So ive setup the monowall ports this way:

eth1 -> Wan (dhcp from isp)
eth2 -> LAN   - 192.168.10.xx
eth3 -> OPT1 - 192.168.20.xx connected to a D-link DWL-2100 AP and enables captive portal for guests

On my firewall ive created a rule on the OPT interface to block all trafic to LAN interface.
Since my DWL-2100 AP uses the subnet 192.168.20.xx how can i make a rule to access from the Lan interface (192.168.10.xx) to this d-link for management ?

Thanks in advance
RS