7-11
# Enable DHCP.
<SwitchA> system-view
[SwitchA] dhcp enable
# Add DHCP server 10.1.1.1 into DHCP server group 1.
[SwitchA] dhcp relay server-group 1 ip 10.1.1.1
# Enable the DHCP relay agent on VLAN-interface 1.
[SwitchA] interface vlan-interface 1
[SwitchA-Vlan-interface1] dhcp select relay
# Correlate VLAN-interface 1 to DHCP server group 1.
[SwitchA-Vlan-interface1] dhcp relay server-select 1
After the preceding configuration is complete, DHCP clients can obtain IP addresses and other
network parameters through the DHCP relay agent from the DHCP server. You can use the
display
dhcp relay statistics
command to view statistics of DHCP packets forwarded by DHCP relay agents.
If invalid IP address check is enabled on the relay agent with the
dhcp relay address-check
command, you can use the
display dhcp relay security
command to view bindings of DHCP relay
agents.
z
Performing the configuration on the DHCP server is also required to guarantee the client-server
communication via the relay agent.
z
Because the DHCP relay agent and server are on different subnets, you need to configure a static
route or dynamic routing protocol to make them reachable to each other.
DHCP Relay Agent Option 82 Support Configuration Example
Network requirements
z
As shown in
, Enable Option 82 on the DHCP relay agent (Switch A).
z
Configure the handling strategy for DHCP requests containing Option 82 as
replace
.
z
Configure the padding content for the circuit ID sub-option as
company001
and for the remote ID
sub-option as
device001
.
z
Switch A forwards DHCP requests to the DHCP server (Switch B) after replacing Option 82 in the
requests, so that the DHCP clients can obtain IP addresses.
Configuration procedure
# Specify IP addresses for the interfaces (omitted).
# Enable DHCP.
<SwitchA> system-view
[SwitchA] dhcp enable
# Add DHCP server 10.1.1.1 into DHCP server group 1.
[SwitchA] dhcp relay server-group 1 ip 10.1.1.1
# Enable the DHCP relay agent on VLAN-interface 1.
[SwitchA] interface vlan-interface 1