How to Configure DHCP on a Cisco Router Example

By | 9th November 2015

How To Assign IP Addresses with DHCP on Cisco Router.

DHCP assigns IP addresses and other important network configuration information to clients dynamically. Cisco router uses the Cisco IOS feature known as Easy IP as an optional DHCP server. Easy IP leases IP configurations to network clients for 24 hours by default.

We use the topology diagram below as sample network topology.

dhcp config

Step 1.

Configure excluded address(es): 

These addresses are reserved for network hosts or clients that need Static Addresses, such as servers, routers and printers. These IP addresses are not included in the address pools that are available for assigning to other clients.

DHCP excluded address on R1

R1#config terminal

R1(config)#ip dhcp excluded-address 192.168.30.1 192.168.30.9

R1(config)#end

R1#

Step 2. 

Configure the address pool: 

Define the pool of addresses from which DHCP assigns addresses to clients on the network. in this case (R1) the available addresses are all addresses on the 192.168.30.0 network, except for the range excluded on step 1.

Configure address pool on R1: define the address pool, default gateway, and DNS server that are assigned to each client requesting for DHCP IP configuration.

R1(config)#ip dhcp pool R1LAN

R1(dhcp-config)#network 192.168.30.0 255.255.255.0

R1(dhcp-config)#default-router 192.168.30.1

R1(dhcp-config)#dns-server 192.168.10.254

R1(dhcp-config)#end

R1#

Do the same on R3 in this case:

Excluded address for R3:

R3(config)#ip dhcp excluded-address 192.168.20.1 192.168.20.9

R3(config)#end

R3#

Address pool for R3:

R3(config)#ip dhcp pool R3LAN

R3(dhcp-config)#network 192.168.20.0 255.255.255.0

R3(dhcp-config)#default-router 192.168.20.1

R3(dhcp-config)#dns-server 192.168.10.254

R3(dhcp-config)#end

R3#

How to Verify the DHCP Address Pool Configuration

Perform this task to verify your DHCP address pool configuration. Use these show commands, they need not be entered in any specific order.

STEP

1. enable 
Example:

Router> enable

This enables the privileged EXEC mode. Enter your password if prompted.

2. show ip dhcp pool [name]show ip dhcppool [name]

Example:

Router# show ip dhcp pool orbitz

This displays information about DHCP address pools.

3. show ip dhcp binding [address]show ip dhcpbinding[address]

Example:

Router# show ip dhcp binding 

This displays a list of all bindings created on a specific DHCP server.

• Use the show ip dhcp binding command to display the IP addresses that have already been assigned.

  • Verify that the address pool has not been exhausted. If necessary, re-create the pool to create a larger pool of addresses.

• Use the show ip dhcp binding command to display the lease expiration date and time of the IP address of the host.
4. show ip dhcp conflict [address]show ip dhcpconflict[address]

Example:

Router# show ip dhcp conflict

This displays a list of all address conflicts.

5. show ip dhcp database [url]show ip dhcpdatabase [url]

Example:

Router# show ip dhcp database

This displays recent activity on the DHCP database.

6. show ip dhcp server statistics [type-number]show ip dhcpserverstatistics[type-number]

Example:

Router# show ip dhcp server statistics

This displays count information about server statistics and messages sent and received.

Defining DHCP Lease Periods on Cisco Router

DHCPv6

How to Configure Static routes on Cisco Router

How to Configure Default Routes on Cisco router

Host Standby Router Redundancy Protocol (HSRP)

Virtual Router Redundancy Protocol (VRRP)

Gateway Load Balancing Protocol (GLBP)

Spanning Tree Protocol (STP)

VLAN Trunking Protocol (VTP)

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