Cisco ASA as DHCP Server with Multiple Internal LANs

[patelparth3]

Internal_network_1                Internal_Network_2
192.168.10.0   -------Firewall-------192.168.20.0
255.255.255.0           |           255.255.255.0
                        |
                        |
                     Internet
                     204.0.0.3

Below is the DHCP configuration for Internal_network_1:

dhcpd address 192.168.10.100-192.168.10.254 Internal_network_1
dhcpd dns 75.75.75.75 75.75.76.76
dhcpd lease 604800
dhcpd ping_timeout 50
dhcpd option 3 ip 192.168.10.1
dhcpd enable Internal_network_1

However now I want to configure DHCP for Internal_network_2 and below is the configuration:

dhcpd address 192.168.20.100-192.168.20.254 Internal_network_2
dhcpd dns 75.75.75.75 75.75.76.76
dhcpd lease 604800
dhcpd ping_timeout 50
dhcpd option 3 ip 192.168.20.1
dhcpd enable Internal_network_2

Issue: How to configure CiscoASA DHCP server on interface e0/0 and interface e0/1 to assign default gateway 192.168.10.1 on DHCP client of Internal_network_1 and 192.168.20.1 on DHCP client of Internal_network_2 respectively. From my research dhcpd option 3 ip 192.168.10.1 will assign default gateway to Internal_network_1 clients but then entering dhcpd option 3 ip 192.168.20.1 for Internal_network_2 will overwrite the previous command and send 192.168.20.1 to both DHCP client of network_1 and network_2. Please advice how to configure ciscoASA as DHCP server to assign default gateway on multiple LANs as per the interface. Thanking you in advance.

PS: CIscoASA is running ver 7.0

[Marius Gunnerud]

When you define the dhcpd option 3 ip command you are manually defining the default-gateway that will be pushed the the DHCP clients of their respective pools.  If you do not define the dhcpd option 3 ip command then the IP of the interface closest to the DHCP clients is used as the default-gateway. 

[david.mulvihill]

Then what is the point of the option 3 command to provide a default gateway if the firewall seems to provide the right IP by default?  What scenario would you want to override it being the interface IP connected to the subnet?