H3C Technologies H3C S5120 Series Switches - Manual (Page 244)

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To do… Use the command… Remarks
Enable the DHCP relay agent
on the current interface
dhcp select relay
Required
With DHCP enabled, interfaces
work in the DHCP server mode.
If the DHCP client obtains an IP address via the DHCP relay agent, the address pool of the subnet to
which the IP address of the DHCP relay agent belongs must be configured on the DHCP server.
Otherwise, the DHCP client cannot obtain a correct IP address.
Correlating a DHCP Server Group with a Relay Agent Interface
To improve reliability, you can specify several DHCP servers as a group on the DHCP relay agent and
correlate a relay agent interface with the server group. When the interface receives requesting
messages from clients, the relay agent will forward them to all the DHCP servers of the group.
Follow these steps to correlate a DHCP server group with a relay agent interface:
To do… Use the command… Remarks
Enter system view system-view —
Create a DHCP server group
and add a server into the group dhcp relay server-group group-id
ip ip-address
Required
Not created by default.
Enter interface view
interface interface-type
interface-number
—
Correlate the DHCP server
group with the current interface
dhcp relay server-select group-id
Required
By default, no interface is
correlated with any DHCP
server group.
z You can specify up to twenty DHCP server groups on the relay agent and up to eight DHCP server
addresses for each DHCP server group.
z The IP addresses of DHCP servers and those of relay agent’s interfaces cannot be on the same
subnet. Otherwise, the client cannot obtain an IP address.
z A DHCP server group can correlate with one or multiple DHCP relay agent interfaces, while a relay
agent interface can only correlate with one DHCP server group. Using the dhcp relay
server-select command repeatedly overwrites the previous configuration. However, if the
specified DHCP server group does not exist, the interface still uses the previous correlation.
z The group-id argument in the dhcp relay server-select command is configure by using the dhcp
relay server-group command.