HP VPN Firewall Appliances Network Management Configuration Guide

191
Item Descri
p
tion
Dynamic Bindings
Refresh
Enable or disable periodic refresh of dynamic client entries, and set the refresh
interval.
Through the DHCP relay agent, a DHCP client sends a DHCP-RELEASE unicast
message to the DHCP server to relinquish its IP address. In this case, the DHCP relay
agent simply conveys the message to the DHCP server and does not remove the
corresponding client entry. To solve this problem, you can enable the periodic
refresh of dynamic client entries.
With this feature, the DHCP relay agent uses the IP address of a client and the MAC
address of the DHCP relay agent 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 considers the IP address assignable now
and ages out the client entry. In addition, upon receiving a DHCP-ACK packet, the
DHCP relay agent sends a DHCP-RELEASE to release the IP address.
• If the server returns a DHCP-NAK message, which means the IP address is still in
use, the relay agent does not age it out.
If the Auto option is selected, the refresh interval is calculated by the relay agent
according to the number of client entries.
Track Timer Interval
Creating a DHCP server group
1. From the navigation tree, select Network > DHCP > DHCP Relay.
The DHCP relay agent configuration page appears, as shown in Figure 114.
2. In the Server Group field, click Add.
T
he page for creating a server group appears.
Figure 115 Creating a server group
3. Configure a DHCP server group as described in Table 27.
4. Click Apply.
Table 27 Configuration items
Item Descri
p
tion
Server Group ID
Enter the ID of a DHCP server group.
You can create up to 20 DHCP server groups.
IP Address
Enter the IP address of a server in the DHCP server group.
The server IP address cannot be on the same subnet as the IP address of the DHCP
relay agent. Otherwise, the client cannot obtain an IP address.