Saturday, 13 October 2012

Basic DHCP Configuration

DHCP is the dominant way of providing end user devices with the information required to connect to your network.

In small or midsize environments DHCP is usually provided through the ISR Router.

Steps needed to deploy DHCP

  1. Define which addresses are going to be excluded. 
  2. Statically configure addresses on Servers and to any device that needs a specific IP address. 
  3. Configure your Router as DHCP relay if a DHCP Server is used or enable the DHCP Service on your router to act as a DHCP Server.

Configuring a DHCP Relay Agent


In case your network has a dedicated platform that provides DHCP services , you should configure on the interface that is the default gateway the command : ip helper-address address

If your DHCP Server has the address then you should type :

Router(config-if)# ip helper-address 

Configuring a DHCP Server on a Cisco Router


Router(config)# ip dhcp excluded-address 
 // excludes the addresses - from being assigned to hosts.
Router(config)# ip dhcp pool DHCP1
// Creates a DHCP Pool named DHCP1 
Router(dhcp-config)# network 
// Defines the Network that is going to be used to provide addresses , here it will use the /24 subnet .
// The default gateway is 
// DNS Server is


The previous commands have this effect : 
  • addresses - .9 are not assigned to hosts
  • The network range is /24
  • The Gateway is
  • DNS server is

 Caution : In order for the DHCP Service to operate you should have configured the interface with an address from the /24 subnet usually the default gateway address /24

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