Enabling Client Offline Detection; Configuring The Dhcp Relay Agent To Release An Ip Address - HP 10500 Series Configuration Manual

compares the chaddr field of a received DHCP request with the source MAC address in the frame
header. If they are the same, the DHCP relay agent decides this request as valid and forwards it to
the DHCP server. If not, it discards the DHCP request.
To enable MAC address check:
Step
1. Enter system view.
2. Enter interface view.
3. Enable
check.
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 may 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 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:
Step
1. Enter system view.
2. Enter interface view.
3. Enable offline detection.
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.
To configure the DHCP relay agent to send DHCP-RELEASE messages:
Step
1. Enter system view.
Command
system-view
interface interface-type
interface-number
MAC address
dhcp relay check mac-address
Command
system-view
interface interface-type
interface-number
dhcp relay client-detect enable
Command
system-view
62
Remarks
N/A
N/A
The default setting is disabled.
Remarks
N/A
N/A
Disabled by default.