3Com Switch 4800G 24-Port Configuration Manual page 816

816 C 58: DHCP R
HAPTER
n
Correlating a DHCP
Server Group with a
Relay Agent Interface
n
Configuring the DHCP
Relay Agent to Send a
DHCP-Release Request
A C
ELAY GENT ONFIGURATION
To do...
Enter system view
Enter interface view
Enable the DHCP relay agent
on the current interface
If the DHCP client obtains an IP address via the DHCP relay agent, the address pool
of the subnet which the IP address of the DHCP relay agent belongs to must be
configured on the DHCP server. Otherwise, the DHCP client cannot obtain a
correct IP address.
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...
Enter system view
Create a DHCP server group
and add a server into the
group
Enter interface view
Correlate the DHCP server
group with the current
interface
You can specify at most twenty DHCP server groups on the relay agent and at
■
most eight DHCP server addresses for each DHCP server group.
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.
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.
The group-id in the dhcp relay server-select command was specified by the
■
dhcp relay server-group command.
Sometimes, you need to release a client's IP address manually on the DHCP relay
agent. With this task completed, the DHCP relay agent can actively send a
DHCP-RELEASE request that contains the client's IP address to be released. Upon
Use the command...
system-view
Interface interface-type
interface-number
dhcp select relay
Use the command...
system-view
dhcp relay server-group
group-id ip ip-address
interface interface-type
interface-number
dhcp relay server-select
group-id
Remarks
-
-
Required
With DHCP enabled,
interfaces work in the DHCP
server mode.
Remarks
-
Required
Not created by default.
-
Required
By default, no interface is
correlated with any DHCP
server group.