PIX/ASA as a DHCP Server and Client Configuration Example

pixfirewall#show running-config 
PIX Version 7.1(1)
!
hostname pixfirewall
domain-name default.domain.invalid
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface Ethernet0
 nameif outside
 security-level 0


!--- Configures the Security Appliance interface as a DHCP client.
!--- The setroute keyword causes the Security Appliance to set the default 
!--- route using the default gateway the DHCP server returns. 

 ip address dhcp setroute

!
interface Ethernet1
 nameif inside
 security-level 100
 ip address 10.0.0.14 255.0.0.0


!--- Output is suppressed. 

Reference: 

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00806c1cd5.shtml