4.Click Apply.

Table 94 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

records 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 re-records server information following this mechanism.

 

 

 

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

 

interval.

Dynamic Bindings

A DHCP client sends a DHCP-RELEASE unicast message to the DHCP server through

Refresh

the DHCP relay agent to relinquish its IP address. In this case the DHCP relay agent

 

simply 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 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

Track Timer Interval

a specific interval, which means that the IP address is assignable now, the DHCP

relay agent ages out the client entry.

 

 

• 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.

 

 

Creating a DHCP server group

1.From the navigation tree, select Network > DHCP to enter the default DHCP Relay page shown in Figure 274.

2.In the Server Group area, click Add to enter the page shown in Figure 275. Figure 275 Create a server group

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