H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 385)

36-5
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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.
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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.
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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.
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The group-id in the dhcp relay server-select command was specified by the dhcp relay
server-group command.
Configuring the DHCP Relay Agent to Send a DHCP-Release Request
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 receiving the DHCP-RELEASE request, the DHCP server then
releases the IP address for the client.
Follow these steps to configure the DHCP relay agent in system view to send a DHCP-RELEASE
request:
To do… Use the command… Remarks
Enter system view system-view —
Configure the DHCP relay agent to send a
DHCP-RELEASE request
dhcp relay release ip client-ip Required
Configuring the DHCP Relay Agent Security Functions
Creating static bindings and enabling IP address check
The DHCP relay agent can dynamically record clients’ IP-to-MAC bindings after clients get IP
addresses. It also supports static bindings, which means you can manually configure IP-to-MAC
bindings on the DHCP relay agent, so that users can access external network using fixed IP addresses.
For avoidance of invalid IP address configuration, you can configure the DHCP relay agent to check
whether a requesting client’s IP and MAC addresses match a binding on it (both dynamic and static
bindings). If not, the client cannot access outside networks via the DHCP relay agent.
Follow these steps to create a static binding and enable IP address check:
To do… Use the command… Remarks
Enter system view system-view —
Create a static binding
dhcp relay security static ip-address
mac-address [ interface interface-type
interface-number ]
Optional
No static binding is created by
default.