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Chapter 75 DHCP Snooping
XGS2220 Series User’s Guide
556
75.4 DHCP Snooping Port Setup
Use this screen to specify whether ports are trusted or untrusted ports for DHCP snooping.
Note: If DHCP snooping is enabled but there are no trusted ports, DHCP requests cannot
reach the DHCP server.
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.
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 enable Option 82 Profile in the SECURITY > DHCP Snooping > DHCP Snp. VLAN
Setup 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. You can enter up to 256 printable ASCII
characters except [ ? ], [ | ], [ ' ], [ " ] or [ , ].
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 Status screen (Section 75.2 on page 552).
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.
Table 288 SECURITY > DHCP Snooping > DHCP Snp. Setup (continued)
LABEL DESCRIPTION
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