2.DHCP service and advanced DHCP relay agent configuration items

Item

Description

DHCP Service

Enable or disable global DHCP.

 

 

 

Enable or disable unauthorized DHCP server detection.

 

There are unauthorized DHCP servers on networks, which reply DHCP clients with

 

wrong IP addresses.

Unauthorized Server

With this feature enabled, upon receiving a DHCP request, the DHCP relay agent will

record the IP address of any DHCP server that assigned an IP address to the DHCP

Detect

client and the receiving interface. The administrator can use this information to check

 

 

out DHCP unauthorized servers. The device puts a record once for each DHCP

 

server. The administrator needs to find unauthorized DHCP servers from the log

 

information. After the information of recorded DHCP servers is cleared, the relay

 

agent will re-record server information following this mechanism.

 

 

 

Enable or disable periodic refresh of dynamic client entries, and set the refresh

 

interval.

 

Via 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

Dynamic Bindings

conveys the message to the DHCP server, thus it does not remove the IP address from

dynamic client entries. To solve this problem, the periodic refresh of dynamic client

Refresh

entries feature is introduced.

 

 

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 specified interval, which means that the IP address is assignable now, the

 

 

DHCP relay agent will age out the client entry.

Track Timer Interval

∙ If the server returns a DHCP-NAK message, which means the IP address is still in

use, the relay agent will not age it out.

 

Note that if the Auto radio button is clicked on, the refresh interval is calculated by the

 

relay agent according to the number of client entries.

 

 

Return to DHCP relay agent configuration task list.

Creating a DHCP server group

Select Network DHCP from the navigation tree to enter the default DHCP Relay page shown in a. In the Server Group field, click Add to enter the page shown in a.

a.Create a server group

282