topic Re: Changing default gateway on ASA5505 DHCP server in Network Security

Changing default gateway on ASA5505 DHCP server

saidfrh — Mon, 11 Mar 2019 12:06:33 GMT

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?

Re: Changing default gateway on ASA5505 DHCP server

abinjola — Thu, 21 Feb 2008 19:40:10 GMT

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

Re: Changing default gateway on ASA5505 DHCP server

saidfrh — Thu, 21 Feb 2008 19:43:30 GMT

How do you change the default gateway?

Thanks.

Re: Changing default gateway on ASA5505 DHCP server

abinjola — Thu, 21 Feb 2008 19:50:17 GMT

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

Re: Changing default gateway on ASA5505 DHCP server

saidfrh — Thu, 21 Feb 2008 20:32:51 GMT

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

Re: Changing default gateway on ASA5505 DHCP server

elparis — Thu, 21 Feb 2008 20:49:01 GMT

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.

Re: Changing default gateway on ASA5505 DHCP server

abinjola — Thu, 21 Feb 2008 22:18:01 GMT

NO thats not possible

Re: Changing default gateway on ASA5505 DHCP server

elparis — Thu, 06 Mar 2008 23:25:32 GMT

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.-