3Com 4210G Series, Configuration Manual, Page: 255 / 1133

6-10
Figure 6-3
Network diagram for DHCP relay agent
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
[SwitchA-Vlan-interface1] dhcp select relay
# Correlate VLAN-interface 1 to DHCP server group 1.
[SwitchA-Vlan-interface1] dhcp relay server-select 1
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 Figure 6-3 , 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 after replacing Option 82 in the requests,
so that the DHCP clients can obtain IP addresses.