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How to Configure DHCP on a Cisco ASA 5505?
Dynamic Host Configuration Protocol (DHCP) is a network application protocol used by devices (DHCP clients) to obtain configuration information for operation in an Internet Protocol network. This protocol reduces system administration workload, allowing devices to be added to the network with little or no manual intervention.
The diagram has the network topology. In this network the firewall is the gateway of the 10.16.74.0/24 network. Firewall and Servers will be excluded from the DHCP pool.
First step is to configure the inside (LAN) interface on the 10.16.74.0/24 network
FIREWALL(config)#interface Vlan1
FIREWALL(config-if)#nameif inside
FIREWALL(config-if)#security-level 100
FIREWALL(config-if)#ip address 10.16.74.1 255.255.255.0
Next assign the LAN ports for the correct VLAN in this case port 1 of firewall will be on VLAN 1
FIREWALL(config)#interface Ethernet0/1
FIREWALL(config-if)#switchport access vlan 1
FIREWALL(config-if)#no shut
Lastly, configure the dhcp range and assign it to an interface. Configure DNS servers, one internal and one external in case the internal fails. Enable DHCP on the inside interface
FIREWALL(config)#dhcpd address 10.16.74.15-10.16.74.35 inside
FIREWALL(config)#dhcpd dns 10.16.74.10 4.2.2.2
FIREWALL(config)#dhcpd enable inside
In order to see which devices are receiving DHCP from the firewall run the following command
FIREWALL(config)#sh dhcpd binding
IP address Hardware address Lease expiration Type
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