Configuring The Dhcp Relay Agent Security Functions; Enabling The Dhcp Relay Agent To Record Relay Entries; Enabling Periodic Refresh Of Dynamic Relay Entries - HP FlexNetwork MSR2003 Configuration Manual

•
The IP address of any specified DHCP server must not reside on the same subnet as the IP
address of the relay interface. Otherwise, the clients might fail to obtain IP addresses.
•
You can specify a maximum of eight DHCP servers.
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 use the 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. Examples of the security functions are ARP address check, authorized ARP, and IP
source guard.
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 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 following information to periodically send a
DHCP-REQUEST message to the DHCP server:
•
The IP address of a relay entry.
•
The MAC address of the DHCP relay interface.
The relay agent maintains the relay entries depending on what it receives from the DHCP server:
Command
system-view
interface interface-type
interface-number
dhcp relay server-address
ip-address
Command
system-view
dhcp relay client-information record
69
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.