To configure the AP as a all-in-one router we'll enable the DHCP server on the AP on a VLAN where all the WLANs will be mapped (so clients get their IP address from this DHCP server), then enable NAT so all traffic going out of the AP will be NAT'ed out of the main IP address the AP has received over DHCP.
(This KB is from Sumans response to a customer query on the main cnPilot forum here)
Step 1: Network -> DHCP -> Create pool
Configure network address range, default gateway and DNS.
Step 2: Network -> VLAN -> Add new interface Create VLAN interface
Configure IP ADDRESS ( same as created as gateway on DHCP), Check the "Hide IP" option to enable NAT so the client will get internet access.
Step 3: Configure -> WLAN, Create wireless SSID for VLAN created. ie. make sure the VLAN mapped to the WLAN is 2 (the one we are giving out IP addresses on)