Changing default gateway on ASA5505 DHCP server

[saidfrh]

How do you configure the default gateway on the ASA5505 DHCP server? By default is the Inside Eth address the deafault gateway? if so can it be changed?

[abinjola]

If you have DHCP configured on inside Innterface of ASA then the DG assigned to internal machines would be its own IP address (ASA 5505), you can change it

[saidfrh]

How do you change the default gateway?

Thanks.

[abinjola]

where do you want to change your DG ? whats configuration on ASA ? Is ASA inside Interface acting as DHCP server ?

[saidfrh]

We have would like the default gateway on the ASA DHCP server to be the MPLS router's Eth int.

[elparis · Accepted solution]

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.

[abinjola]

NO thats not possible

[elparis · Accepted solution]

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.-