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19-8
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-09
Chapter 19 Configuring DHCP Features
Configuring DHCP Features
Beginning in privileged EXEC mode, follow these steps to specify the packet forwarding address. This
procedure is optional.
To remove the DHCP packet forwarding address, use the no ip helper-address address interface
configuration command.
This example shows how to enable the DHCP server, the relay agent, and the insertion and removal of
the DHCP relay information (option 82). It creates a switch virtual interface with VLAN ID 10, assigns
it an IP address, and specifies the DHCP packet forwarding address of 30.0.0.2 (DHCP server address).
Two interfaces (Gigabit Ethernet 0/1 and 0/2) that connect to the DHCP clients are configured as static
access ports in VLAN 10 (see
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# service dhcp
Switch(config)# ip dhcp relay information option
Switch(config)# interface vlan 10
Switch(config-if)#
ip address 10.0.0.1 255.0.0.0
Switch(config-if)# ip helper-address 30.0.0.2
Switch(config-if)# exit
Switch(config)# interface range gigabitethernet0/1 - 2
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 10
Switch(config-if)# exit
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface vlan vlan-id
Enter interface configuration mode, and create a switch virtual interface.
Step 3
ip address ip-address subnet-mask
Configure the interface with an IP address and an IP subnet.
Step 4
ip helper-address address
Specify the DHCP packet forwarding address.
The helper address can be a specific DHCP server address, or it can be
the network address if other DHCP servers are on the destination
network segment. Using the network address enables other servers to
respond to DHCP requests.
If you have multiple servers, you can configure one helper address for
each server.
Step 5
exit
Return to global configuration mode.
Step 6
interface range port-range
or
interface interface-id
Configure multiple physical ports that are connected to the DHCP
clients, and enter interface range configuration mode.
or
Configure a single physical port that is connected to the DHCP client,
and enter interface configuration mode.
Step 7
switchport mode access
Define the VLAN membership mode for the port.
Step 8
switchport access vlan vlan-id
Assign the ports to the same VLAN as configured in Step 2.
Step 9
end
Return to privileged EXEC mode.
Step 10
show running-config
Verify your entries.
Step 11
copy running-config startup-config
(Optional) Save your entries in the configuration file.