Dynamic Host Configuration Protocol (DHCP) is a protocol used to automatically assign IP addresses to end-user devices in a network.
Apart from using a dedicated server for DHCP service in a network, a Cisco router can also be used as a DHCP server. It just needs an extra bit of configuration.
In this post, I will show you how to configure a DHCP server on a Cisco router.
DHCP servers provide a lot of information to the end-user device when the device is first connected to a network that has DHCP service enabled. Such information includes: IP address, subnet mask, domain name, default gateway, DNS server address, and WIN server address.
Network Topology
The network topology we are going to be making use of in this demonstration is shown below. As you can see, it consists of a Cisco router, a switch, and three PCs. In this demonstration, We will be configuring the router as a DHCP server.
Step 2: Enable DHCP service on the router
After creating the network topology, the next step is to enable the DHCP service on the router.
DHCP_Router>enable
DHCP_Router#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
DHCP_Router(config)# service dhcp
Step 3: Create a DHCP pool on the router.
In this step, we create a DHCP pool from which the IP addresses will be assigned to the client/end-user device. We will use the pool name “NET-A” and configure it to advertise IP addresses from the network (192.168.1.0/24) for automatic IP address configuration on DHCP-enabled host devices.
DHCP_Router(config)# ip dhcp pool NET_A
DHCP_Router(config)# network 192.168.1.0 255.255.255.0
DHCP_Router(config)# default-router 192.168.1.1
DHCP_Router(config)# dns-server 192.168.1.2
Step 4: Configure excluded addresses
In this step, we will configure some excluded IP addresses from the range of IP addresses available in the DHCP pool. Excluded addresses are reserved for important hosts, like a server that needs to maintain a static IP address. Normally, these reserved IP addresses are configured manually on the devices for which they are reserved.
In this demonstration, we will exclude the router’s interface IP address “192.168.1.1” and the 192.168.1.250 and 192.168.1.255 address ranges, from which we manually assign addresses to servers in our network.
DHCP_Router(config)# ip dhcp excluded-address 192.168.1.1
DHCP_Router(config)# ip dhcp excluded-address 192.168.1.250 192.168.1.255
Step 5: Verify the client is served by the DHCP server.
To do this, you use the command below:
DHCP_Router#show ip dhcp binding
Step 6: Verify connectivity.
You check if all the hosts are connected to each other by pinging from one host to another.
Configuring a Cisco Router as a DHCP Client
In addition to a Cisco router serving as a DHCP server, you can also configure it as a DHCP client. This means the interface will request an IP address using the standard DHCP process, and any DHCP server on the network will lease an IP address to it.
This is done using the following command:
DHCP_Router(config)# int FastEthernet0/0
DHCP_Router(config-if)#ip address dhcp
Related Content:
How to Configure DHCP on Layer 2 Switch in Packet Tracer
How to Configure DHCP on Layer 3 Switch In Packet Tracer
How to Configure DHCP Server For Multiple VLANS in Packet Tracer
How to Configure DHCP Snooping In Cisco Packet Tracer
How to Configure DHCP Relay Agent on Layer 3
How to Configure DHCP on Layer 3 Switch In Packet Tracer

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