To improve security and avoid malicious attack to the unused SOCKETs, the device provides the following functions:

zUDP 67 and UDP 68 ports used by DHCP are enabled only when DHCP is enabled.

zUDP 67 and UDP 68 ports are disabled when DHCP is disabled.

The corresponding implementation is as follows:

zWhen a VLAN interface is mapped to a DHCP server group with the dhcp-servercommand, the DHCP relay agent is enabled. At the same time, UDP 67 and UDP 68 ports used by DHCP are enabled.

zWhen the mapping between a VLAN interface and a DHCP server group is removed with the undo dhcp-servercommand, DHCP services are disabled. At the same time, UDP 67 and UDP 68 ports are disabled.

z z

z

z

You can configure up to eight DHCP server IP addresses in a DHCP server group.

You can map multiple VLAN interfaces to one DHCP server group. But one VLAN interface can be mapped to only one DHCP server group.

If you execute the dhcp-server groupNo command repeatedly, the new configuration overwrites the previous one.

You need to configure the group number specified in the dhcp-server groupNo command in VLAN interface view by using dhcp-server groupNo ip ip-address&<1-8>in advance.

Configuring DHCP Relay Agent Security Functions

Configuring address checking

After relaying an IP address from the DHCP server to a DHCP client, the DHCP relay agent can automatically record the client’s IP-to-MAC binding and generate a dynamic address entry. 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.

The purpose of the address checking function on DHCP relay agent is to prevent unauthorized users from statically configuring IP addresses to access external networks. With this function enabled, a DHCP relay agent inhibits a user from accessing external networks if the IP address configured on the user end and the MAC address of the user end do not match any entries (including the entries dynamically tracked by the DHCP relay agent and the manually configured static entries) in the user address table on the DHCP relay agent.

Follow these steps to configure address checking:

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3Com WX3000 operation manual Configuring Dhcp Relay Agent Security Functions, Configuring address checking