ZyXEL Communications MES3500 Series, User Manual

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Chapter 27 IP Source Guard
MES3500 Series User’s Guide
225
Figure 126
Advanced Application > IP Source Guard > DHCP Snooping Configure
The following table describes the labels in this screen.
Table 90
Advanced Application > IP Source Guard > DHCP Snooping Configure
LABEL DESCRIPTION
Active Select this to enable DHCP snooping on the Switch. You still have to enable DHCP
snooping on specific VLAN and specify trusted ports.
Note: The Switch will drop all DHCP requests if you enable DHCP snooping and there are
no trusted ports.
DHCP Vlan Select the second option and specify a VLAN ID if you want the Switch to forward DHCP
packets to DHCP servers on a specific VLAN.
Note: You have to enable DHCP snooping on the DHCP VLAN too.
You can enable Option82 in the DHCP Snooping VLAN Configure screen ( Section
27.5.2 on page 227 ) to help the DHCP servers distinguish between DHCP requests from
different VLAN.
Select Disable if you do not want the Switch to forward DHCP packets to a specific
VLAN.
Database If Timeout interval is greater than Write delay interval , it is possible that the next
update is scheduled to occur before the current update has finished successfully or
timed out. In this case, the Switch waits to start the next update until it completes the
current one.
Agent URL Enter the location of the DHCP snooping database. The location should be expressed
like this:
tftp://{domain name or IP address}/directory, if applicable/file
name ; for example, tftp://192.168.10.1/database.txt.
Timeout interval Enter how long (10-65535 seconds) the Switch tries to complete a specific update in
the DHCP snooping database before it gives up.
Write delay
interval
Enter how long (10-65535 seconds) the Switch waits to update the DHCP snooping
database the first time the current bindings change after an update. Once the next
update is scheduled, additional changes in current bindings are automatically included
in the next update.