How to configure DHCP on a Cisco router or layer 3 switchPosted on 29 August 2017 by Beaming Support
DHCP (dynamic host configuration protocol) allows a server to assign an IP address to a computer from a preselected range of numbers configured for a particular network.
You can configure DHCP on a Cisco router or layer 3 Switch using the following commands.
In this example we will assume a router is used.
The first thing to do is exclude any important addresses like servers, access points and the router itself. Below we specify a beginning address and an end address to exclude a range of IPs.
Router#conf t Router#(config)ip dhcp excluded-address 192.168.1.1 192.168.1.20 Router#(config)ip dhcp excluded-address 192.168.1.200 192.168.1.254
Next we will set up the DHCP pool and a number of variables.
Router#(config)ip dhcp pool MyDHCP Router#(dhcp-config)network 192.168.1.0 255.255.255.0 Router#(dhcp-config)dns-server 192.168.1.253 Router#(dhcp-config)default-router 192.168.1.254
Here we have specified the IP address range (192.168.1.0/24), the DNS server and the default gateway given out to clients. Providing the router setup is correct, this will allow clients to access the Internet.
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There are further options that can be specified below:
Router(dhcp-config)# domain-name MyNetwork
Lease Time 7 days
Router(dhcp-config)# lease 7
Lease Time 12 hours
Router(dhcp-config)# lease 0 12
To see DHCP leases that have been assigned, issue the following command.
Router#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-id/hardware address Lease expiration Type
192.168.1.21 0010.f752.e77d.10 Aug 20 2019 00:01AM Automatic
192.168.1.22 0010.f752.e7ab.10 Aug 20 2019 00:09AM Automatic
192.168.1.23 0010.f752.e7a4.10 Aug 20 2019 00:51AM Automatic