3Com Switch 4800G 24-Port - Page 817

Configuring the DHCP Relay Agent 817
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:
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:
n
■ The dhcp relay address-check enable command is independent of other
commands of the DHCP relay agent. That is, the invalid address check takes
effect when this command is executed, regardless of whether other commands
are used.
■ You are recommended to configure IP address check on the interface enabled
with the DHCP relay agent; otherwise, the valid DHCP clients may not be
capable of accessing networks.
■ When using the dhcp relay security static command to bind a VLAN
interface to a static binding entry, make sure that the VLAN interface is
configured as a DHCP relay agent; otherwise, address entry conflicts may occur.
Configuring dynamic binding update interval
Via the DHCP relay agent, a DHCP client sends a DHCP-RELEASE unicast message
to the DHCP server to relinquish its IP address. In this case the DHCP relay agent
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
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.
Enter interface view interface interface-type interface-number -
Enable invalid IP
address check
dhcp relay address-check { disable |
enable }
Required
Disabled by default.