Shahid,

To configure Cisco IOS DHCP, follow these steps, which include sample commands:

1. Configure an IP address on the router's Ethernet port, and bring up the interface. (On an existing router, you would have already done this.)
   

Router(config)# interface ethernet0/0
Router(config-if)#ip address 1.1.1.1 255.0.0.0
Router(config-if)# no shutdown

2. Create a DHCP IP address pool for the IP addresses you want to use.
   

Router(config)# ip dhcp pool mypool

3. Specify the network and subnet for the addresses you want to use from the pool.
   

Router(dhcp-config)# network 1.1.1.0 /8  

4. Specify the DNS domain name for the clients.
   

Router(dhcp-config)#domain-name mydomain.com

5. Specify the primary and secondary DNS servers.
   

Router(dhcp-config)#dns-server 1.1.1.10 1.1.1.11

6. Specify the default router (i.e., default gateway).
   

Router(dhcp-config)#default-router 1.1.1.1

7. Specify the lease duration for the addresses you're using from the pool.
   

Router(dhcp-config)#lease 7

8. Exit Pool Configuration Mode.
   

Router(dhcp-config)#exit

Hope this helps,

David