Try setting DHCP option 3. Don't know if it'll work in routed mode. The documentation states using DHCP option 3 is the way to set a default gateway in transparent mode. See this section of the documentation:

http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/dhcp.html#wp1059065

Step 7 there states:

Step 7 (Transparent Firewall Mode) Define a default gateway. To define the default gateway that is sent to DHCP clients, enter the following command.

hostname(config)# dhcpd option 3 ip gateway_ip

If you do not use the DHCP option 3 to define the default gateway, DHCP clients use the IP address of the management interface. The management interface does not route traffic.

Please let us know how it goes.

Sorry for the delay; it took me a couple of weeks to finally be able to try this in the lab...

It is actually possible to configure the DHCP server on a PIX/ASA to provide a default gateway that is different from itself. For example, you could configure the PIX/ASA to send via DHCP a default gateway that is a router or another PIX/ASA.

To do this you use the command "dhcpd option 3 ip " as I originally suggested.

I wasn't sure because I thought I had read somewhere that the PIX/ASA didn't support. Perhaps that was true in pre-7.x software, but I just tested on 7.2.x and it worked just fine.

Cheers,

Eloy Paris.-