3Com Switch 8800 Advanced Software V5 Configuration Guide

738 CHAPTER 51: DHCP RELAY AGENT CONFIGURATION
receiving the DHCP-RELEASE request, the DHCP server then releases the IP address
for the client.
With this feature enabled in system view, the DHCP-RELEASE request will be sent
to those DHCP servers correlated with the DHCP relay agent interfaces.
To configure the DHCP relay agent in system view to send a DHCP-RELEASE
request, use the following commands:
Configuring the DHCP
Relay Agent Security
Functions
Create static bindings and enable invalid IP address check
The DHCP relay agent dynamically records clients’ IP-to-MAC bindings to generate
a dynamic binding after clients got IP addresses. It also supports static binding,
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.
To create a static binding and enable invalid IP address check, use the following
commands:
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.
■ Before executing the dhcp relay address-check enable command on the
DHCP relay interface connected to the DHCP server, you need to configure the
static binding between the IP address and MAC address of the DHCP server.
Otherwise, the DHCP client will fail to obtain an IP address.
To do... Use the command... Remarks
Enter system view system-view -
Configure the DHCP relay
agent in system view 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
Optional
No static binding is
created by default
Enter VLAN interface view interface vlan-interface
interface-number
-
Enable invalid IP address
check
dhcp relay address-check { enable
| disable }
Required
Disabled by default