HP VPN Firewall Appliances Network Management Configuration Guide

200
Ste
p
Command Remarks
2. Enter interface view.
interface interface-type
interface-number
N/A
3. Enable MAC address check.
dhcp relay check mac-address
The default setting is
disabled.
A DHCP relay agent changes the source MAC addresses of DHCP packets before forwarding
them out. Therefore, enable MAC address check only on the DHCP relay agent directly connected
to the DHCP clients. If you enable this feature on an intermediate relay agent, it might discard valid
DHCP packets and the sending clients do not obtain IP addresses.
Enabling client offline detection
With this feature enabled, the DHCP relay agent considers that a DHCP client goes offline when the ARP
entry for the client ages out. In addition, it removes the client entry and sends a DHCP-RELEASE message
to the DHCP server to release the IP address of the client.
To enable offline detection:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enter interface view.
interface interface-type
interface-number
N/A
3. Enable offline detection.
dhcp relay client-detect enable Disabled by default.
Removing an ARP entry manually does not remove the corresponding client's IP-to-MAC binding. When
the client goes offline, use the undo dhcp relay security command to remove the IP-to-MAC binding
manually.
Configuring the DHCP relay agent to release an IP address
You can configure the relay agent to release a client's IP address. The relay agent sends a
DHCP-RELEASE message that contains the specified IP address. Upon receiving the DHCP-RELEASE
message, the DHCP server releases the IP address. Meanwhile, the client entry is removed from the
DHCP relay agent. The IP address to be released must be available in a dynamic client entry.
To configure the DHCP relay agent to send DHCP-RELEASE messages:
Ste
p
Command
1. Enter system view.
system-view
2. Configure the DHCP relay agent to release an IP address.
dhcp relay release ip client-ip
Dynamic client entries can be generated only after you enable address check on the DHCP relay agent.
Configuring the DHCP relay agent to handle Option 82
1. Configuration prerequisites.
Before performing this configuration, complete the following tasks:
a. Enable DHCP.
b. Enable the DHCP relay agent on the specified interface.
c. Correlate a DHCP server group with relay agent interfaces.