ZyXEL Communications GS2220-10, User Manual

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Chapter 27 DHCP Snooping
GS2220 Series User’s Guide
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The following table describes the labels in this screen.
27.3.1 DHCP Snooping Port Configure
Use this screen to specify whether ports are trusted or untrusted ports for DHCP snooping.
Note: The Switch will drop all DHCP requests if you enable DHCP snooping and there are no
trusted ports.
You can also specify the maximum number for DHCP packets that each port (trusted or untrusted) can
receive each second.
To open this screen, click Advanced Application > IP Source Guard > IPv4 Source Guard Setup > DHCP
Snooping > Configure > Port .
Table 122 Advanced Application > IP Source Guard > IPv4 Source Guard Setup > 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 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 select an option 82 profile in the DHCP Snooping VLAN Configure screen 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.
Renew DHCP
Snooping URL
Enter the location of a DHCP snooping database, and click Renew if you want the Switch to
load it. You can use this to load dynamic bindings from a different DHCP snooping
database than the one specified in
Agent URL .
When the Switch loads dynamic bindings from a DHCP snooping database, it does not
discard the current dynamic bindings first. If there is a conflict, the Switch keeps the
dynamic binding in volatile memory and updates the
Binding collisions counter in the DHCP
Snooping screen.
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.