Command
IP Helper-Address
Use
This command is used to enable the router to forward BOOTP broadcast (and other)packets to a specific host.
Syntax
Router(config-if)#ip helper-address <ip address>
Example
In this example, we will configure R1 to provide DHCP services. After that we will configure R3’s Fa0/0 interface to receive an IP address from R1’s DHCP pool.
R1(config)#ip dhcp pool VLAN_A |
We see below that, even we configure R3 to get its interface via DHCP, because the DHCP server is more then one hop away, we will need to use a helper-address.
R3(config-if)#do show ip interface brief | ex unass R3(config)#int fa0/0 |
Now we configure a helper-address on R2’s Fa1/0 because it will be the interface that receives the broadcast from R3.
R2(config-if)#int fa1/0 R2(config-if)#ip helper-address 10.1.1.1 |
Now we will flap the interface on R3 to resend the DHCP information.
R3(config-if)#shut R3(config-if)# R3(config-if)#do sh ip int brief | ex unass R1(config)#do sh ip dhcp bind |