How To Configure DHCP Server On A Cisco Router
First step is to enable the DHCP service on our router, which by default is enabled:
R1# configure terminal
R1(config)# service dhcp
Next step is to create the DHCP pool that defines the network of IP addresses that will be given out to the clients. Note that 'NET-POOL' is the name of the DHCP IP Pool we are creating:
R1(config)# ip dhcp pool NET-POOL
R1(dhcp-config)# network 192.168.1.0 255.255.255.0
This tells the router to issue IP addresses for the network 192.168.1.0, which translates to the range 192.168.1.1 - 192.168.1.254. We will have to exclude the IP addresses we want later on.
We now define the DHCP parameters that will be given to each client. These include the default gateway (default-router), dns servers, domain and lease period (days):
R1(dhcp-config)# default-router 192.168.1.1
R1(dhcp-config)# dns-server 192.168.1.5 195.170.0.1
R1(dhcp-config)# domain-name Firewall.cx
R1(dhcp-config)# lease 9
The 'domain-name' and 'lease' parameters are not essential and can be left out. By default, the lease time for an IP address is one day.
All we need now is to exclude the IP addresses we don't want our DHCP server giving out. Drop back to 'global configuration mode' and enter the following:
R1(config)# ip dhcp excluded-address 192.168.1.1 192.168.1.5
R1(config)# ip dhcp excluded-address 192.168.1.10
This excludes IP addresses 192.168.1.1 - 192.168.1.5 & 192.168.1.10. As you can see, there's an option to exclude a range of IP addresses or a specific address.
The above configuration is all you need to get the DHCP server running for your network. We'll provide a few more commands you can use to troubleshoot and ensure it's working correctly.
The following command will allow you to check which clients have been served by the DHCP:
R1# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
192.168.1.6 0100.1e7a.c409 Jan 19 2009 03:06 PM Automatic
192.168.1.7 0100.1e7a.c3c1 Jan 19 2009 09:00 PM Automatic
192.168.1.8 0100.1ebe.923b Jan 19 2009 02:25 PM Automatic
192.168.1.9 0100.1b53.5ccc Jan 19 2009 02:03 PM Automatic
192.168.1.11 0100.1e7a.261d Jan 19 2009 07:52 PM Automatic
R1#
Notice that IP addresses 192.168.1.5 & 192.168.1.10 have not been assigned to the clients.
