ZyXEL Communications Plumbing Product metrogigabit switch User Manual

 Chapter 26 IP Source Guard

MGS3700-12C User’s Guide

The following table describes the labels in this screen.

Use this screen to enable DHCP snooping on each VLAN and to specify whether or 
not the Switch adds DHCP relay agent option 82 information (

) to DHCP requests that the Switch relays to a DHCP server for each VLAN. To 

Table 85   DHCP Snooping Port Configure

Port

This field displays the port number. If you configure the * port, 
the settings are applied to all of the ports.

Server Trusted state

Select whether this port is a trusted port (Trusted) or an 
untrusted port (Untrusted).

Trusted ports are connected to DHCP servers or other switches, 
and the Switch discards DHCP packets from trusted ports only if 
the rate at which DHCP packets arrive is too high.

Untrusted ports are connected to subscribers, and the Switch 
discards DHCP packets from untrusted ports in the following 
situations:

• The packet is a DHCP server packet (for example, OFFER, ACK, 

or NACK).

• The source MAC address and source IP address in the packet 

do not match any of the current bindings.

• The packet is a RELEASE or DECLINE packet, and the source 

MAC address and source port do not match any of the current 

bindings.

• The rate at which DHCP packets arrive is too high.

Rate (pps)

Specify the maximum number for DHCP packets (1-2048) that 
the Switch receives from each port each second. The Switch 
discards any additional DHCP packets. Enter 0 to disable this 
limit, which is recommended for trusted ports.

Apply

Click Apply to save your changes to the Switch’s run-time 
memory. The Switch loses these changes if it is turned off or loses 
power, so use the Save link on the top navigation panel to save 
your changes to the non-volatile memory when you are done 
configuring.

Cancel

Click this to reset the values in this screen to their last-saved 
values.