Cisco catalyst 3750 Command Reference Manual page 255

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
Usage Guidelines The DHCP snooping binding database can have up to 8192 bindings.
To ensure that the lease time in the database is accurate, we recommend that Network Time Protocol
(NTP) is enabled and configured for these features:
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If NTP is configured, the switch writes binding changes to the binding file only when the switch system
clock is synchronized with NTP.
Because both NVRAM and the flash memory have limited storage capacities, we recommend that you
store a binding file on a TFTP server. You must create an empty file at the configured URL on
network-based URLs (such as TFTP and FTP) before the switch can first write bindings to the binding
file at that URL.
Use the ip dhcp snooping database flash[number]:/filename command to save the DHCP snooping
binding database in the stack master NVRAM. The database is not saved in a stack member NVRAM.
If you set the ip dhcp snooping database timeout command to 0 seconds and the database is being
written to a TFTP file, if the TFTP server goes down, the database agent continues to try the transfer
indefinitely. No other transfer can be initiated while this one is in progress. This might be
inconsequential because if the server is down, no file can be written to it.
Use the no ip dhcp snooping database command to disable the agent.
Use the no ip dhcp snooping database timeout command to reset the timeout value.
Use the no ip dhcp snooping database write-delay command to reset the write-delay value.
Examples
This example shows how to store a binding file at an IP address of 10.1.1.1 that is in a directory called
directory. A file named file must be present on the TFTP server.
Switch(config)# ip dhcp snooping database tftp://10.1.1.1/directory/file
This example shows how to store a binding file called file01.txt in the stack master NVRAM:
Switch(config)# ip dhcp snooping database flash:file01.txt
You can verify your settings by entering the show ip dhcp snooping database privileged EXEC
command.
Related Commands Command
ip dhcp snooping
ip dhcp snooping binding
show ip dhcp snooping database
OL-8552-07
NTP authentication
NTP peer and server associations
NTP broadcast service
NTP access restrictions
NTP packet source IP address
Description
Enables DHCP snooping on a VLAN.
Configures the DHCP snooping binding database.
Displays the status of DHCP snooping database agent.
Catalyst 3750 Switch Command Reference
ip dhcp snooping database
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