How to configure DHCP server on Cisco Routers and switches with Cisco IOS

DHCP, Dynamic Host Configuration Protocol is the protocol used by network devices like a PC or a printer (DHCP clients) to obtain IP Address, Default Gateway, Domain Name, DNS Servers, NetBIOS servers and more that helps the device to work properly in an IP Network.

While in an ideal scenario, most if not all organisations run the DHCP server on a Windows server or a Linux/Unix server. While this is justfiable in bigger corporate and enterprise networks, a smaller network like a branch office can be supported by a local Router, Switch or a Firewall can run a DHCP server without the need of an additional server hardware to run DHCP. Most of the routers, firewalls and some switches do have a DHCP server builtin. Most of the new Cisco Routers and Switches running Cisco IOS can run a DHCP server.

The following procedure helps you to setup a Cisco Router or a Catalyst Switch as DHCP server (I use a Cisco Router here):

Enable DHCP Service on the Router

dhcp-router# conf t

dhcp-router(config)# service dhcp

Create DHCP IP Pool

dhcp-router(config)# ip dhcp pool IP-POOL

where IP-POOL is the name of the DHCP IP Pool

Add Network & subnet mask to the DHCP Pool

dhcp-router(dhcp-config)# network 192.168.1.0 /24

Add Default Gateway for the clients

dhcp-router(dhcp-config)# default-router

Specify the Domain Name for the clients

dhcp-router(dhcp-config)# domain-name mycompany.com

Specify the DNS Servers for the Clients

dhcp-router(dhcp-config)# dns-server 192.168.1.10 192.168.1.11

where 192.16.1.10&11 are the IP address of the local DNS servers

Specify the NetBIOS WINS Servers for the Clients (if any)

dhcp-router(dhcp-config)# netbios-name-server 192.168.1.12

where 192.16.1.12 is the Microsoft WINS server

Set the lease period

dhcp-router(dhcp-config)# lease 8

Sets the Lease for 8 days.

Add Exclusion list (if any)

dhcp-router(config)# ip dhcp exclude-address 192.168.1.25 192.168.1.35

Where 192.168.1.25 & 192.168.1.35 are the Start and End IPs for the range of IPs to be excluded.

This will configure the DHCP server on a Cisco Router or Switch.