Configuring The Dhcp Relay Agent Security Functions; Enabling The Dhcp Relay Agent To Record Relay Entries; Enabling Periodic Refresh Of Dynamic Relay Entries - H3C MSR 2600 Configuration Manual

To specify a DHCP server address on a relay agent:
Step
1. Enter system view.
2. Enter interface view.
3. Specify a DHCP server
address on the relay agent.
Configuring the DHCP relay agent security
functions

Enabling the DHCP relay agent to record relay entries

Perform this task to enable the DHCP relay agent to automatically record clients' IP-to-MAC bindings
(relay entries) after they obtain IP addresses through DHCP.
Some security functions, such as ARP address check, authorized ARP, and IP source guard, use the
recorded relay entries to check incoming packets and block packets that do not match any entry. In this
way, illegal hosts are not able to access external networks through the relay agent.
To enable the DHCP relay agent to record relay entries:
Step
1. Enter system view.
2. Enable the relay agent to
record relay entries.
NOTE:
The DHCP relay agent does not record IP-to-MAC bindings for DHCP clients running on
synchronous/asynchronous serial interfaces.

Enabling periodic refresh of dynamic relay entries

A DHCP client unicasts a DHCP-RELEASE message to the DHCP server to release its IP address. The
DHCP relay agent simply conveys the message to the DHCP server and does not remove the IP-to-MAC
entry of the client.
With this feature, the DHCP relay agent uses the IP address of a relay entry and the MAC address of the
DHCP relay interface to periodically send a DHCP-REQUEST message to the DHCP server.
If the server returns a DHCP-ACK message or does not return any message within a specific interval,
•
the DHCP relay agent removes the relay entry. In addition, upon receiving the DHCP-ACK message,
the relay agent sends a DHCP-RELEASE message to release the IP address.
If the server returns a DHCP-NAK message, the relay agent keeps the relay entry.
•
Command
system-view
interface interface-type
interface-number
dhcp relay server-address
ip-address
Command
system-view
dhcp relay client-information record
58
Remarks
N/A
N/A
By default, no DHCP server
address is specified on the relay
agent.
Remarks
N/A
By default, the relay agent
does not record relay entries.