CLI Reference Guide-R04

Chapter 30 | DHCP Commands
DHCP Relay Option 82
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Default Setting
Enabled
Example
Console(config)#ip dhcp l3 relay
Console(config)#
ip dhcp relay server This command specifies the DHCP server or relay server addresses to use. Use the
no form to clear all addresses.
Syntax
ip dhcp relay server address1 [address2 [address3 ...]]
no ip dhcp relay server
address - IP address of DHCP server. (Range: 1-5 addresses)
Default Setting
None
Command Mode
Global Configuration
Usage Guidelines
◆ DHCP relay service applies to DHCP client requests received on any configured
VLAN, both the management VLAN and non-management VLANs.
◆ This command is used to configure DHCP relay for host devices attached to the
switch. If DHCP relay service is enabled (using the ip dhcp relay information
option command), and this switch sees a DHCP client request, it inserts its own
IP address into the request so that the DHCP server will know the subnet where
the client is located. Then, the switch forwards the packet to a DHCP server on
another network. When the server receives the DHCP request, it allocates a free
IP address for the DHCP client from its defined scope for the DHCP client’s
subnet, and sends a DHCP response back to the DHCP relay agent (i.e., this
switch). This switch then passes the DHCP response received from the server to
the client.
◆ You must specify the IP address for at least one active DHCP server. Otherwise,
the switch’s DHCP relay agent will not be able to forward client requests to a
DHCP server. Up to five DHCP servers can be specified in order of preference.
If any of the specified DHCP server addresses are not located in the same
network segment with this switch, use the ip default-gateway or ipv6 default-
gateway command to specify the default router through which this switch can
reach other IP subnetworks.