Configuring the ASA as a DHCP server is a very needed item in small office deployments.
Recently I had to configure an ASA to hand out a Different default gateway for a while. I was perplexed at how to do this because by default the ASA will hand out the Management interface as its default gateway. Option 3 is the fix to this problem. Below I will show how to configure DHCP on the ASA but also how to change the default gateway handed out by the ASA.
In this example my ASA is at 192.168.5.1, my range of IPs I want to give out are 192.168.5.10-100, and my new default gateway will be 192.168.5.2
dhcpd address 192.168.5.10-192.168.5.100 inside
dhcpd dns 192.168.5.10 18.104.22.168
dhcpd lease 3600
dhcpd enable inside
The option I was talking about was option 3 – this allows a different
default gateway to be added.
dhcpd option 3 ip 192.168.5.2