Configure Cisco router as DHCP server

Dynamic Host Configuration Protocol (DHCP) is an application layer protocol used to distribute various network configuration parameters to devices on a TCP/IP network. – IP addresses, subnet masks, default gateways, DNS servers, etc. DHCP employs a client-server architecture; a DHCP client is configured to request network parameters from a DHCP server on the network. A DHCP server is configured with a pool of available IP addresses and assigns one of them to the DHCP client.

A Cisco router can be configured as a DHCP server. Here are the steps:

  1. Exclude IP addresses from being assigned by DHCP by using the ip dhcp excluded-address FIRST_IP LAST_IP
  2. Create a new DHCP pool with the ip dhcp pool NAME command.
  3. Define a subnet that will be used to assign IP addresses to hosts with the network SUBNET SUBNET_MASK command.
  4. Define the default gateway with the default-router IP command.
  5. Define the DNS server with the dns-server IP address command.
  6. (Optional) Define the DNS domain name by using the ip domain-name NAME command.
  7. (Optional) Define the lease duration by using the lease DAYS HOURS MINUTES command. If you don’t specify this argument, the default lease time of 24 hours will be used.


Here is an example configuration:

Floor1(config)#ip dhcp excluded-address
Floor1(config)#ip dhcp pool Floor1DHCP

In the example above you can see that I’ve configured the DHCP server with the following parameters:

  • the IP addresses from the – range will not be assigned to hosts
  • the DHCP pool was created and named Floor1DHCP
  • the IP addresses assigned to the hosts will be from the range
  • the default gateway’s IP address is
  • the DNS server’s IP address is


To view information about the currently leased addresses, you can use the show ip dhcp binding command:

Floor1#show ip dhcp binding
IP address Client-ID/ Lease expiration Type
Hardware address 0060.5C2B.3DCC -- Automatic

In the output above you can see that there is a single DHCP client that was assigned the IP address of Since we’ve excluded the IP addresses from the – range, the device got the first address available –

To display information about the configured DHCP pools, you can use the show ip dhcp pool command:

Floor1#show ip dhcp pool
Pool Floor1DHCP :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 1
Excluded addresses : 1
Pending event : none

1 subnet is currently in the pool
Current index IP address range Leased/Excluded/Total - 1 / 1 / 254

This command displays some important information about the DHCP pool(s) configured on the device – the pool name, total number of IP addresses, the number of leased and excluded addresses, subnet’s IP range, etc.

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