Catalyst 3750-E and 3560-E Switch Cisco IOS ... - DNIP . NET

ip dhcp snooping databaseChapter 2Catalyst 3750-E and 3560-E Switch Cisco IOS CommandsUsage GuidelinesThe 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:• NTP authentication• NTP peer and server associations• NTP broadcast service• NTP access restrictions• NTP packet source IP addressIf NTP is configured, the switch writes binding changes to the binding file only when the switch systemclock is synchronized with NTP.Because both NVRAM and the flash memory have limited storage capacities, we recommend that youstore a binding file on a TFTP server. You must create an empty file at the configured URL onnetwork-based URLs (such as TFTP and FTP) before the switch can first write bindings to the bindingfile at that URL.Use the ip dhcp snooping database flash[number]:/filename command to save the DHCP snoopingbinding 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 beingwritten to a TFTP file, if the TFTP server goes down, the database agent continues to try the transferindefinitely. No other transfer can be initiated while this one is in progress. This might beinconsequential 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.ExamplesThis example shows how to store a binding file at an IP address of 10.1.1.1 that is in a directory calleddirectory. A file named file must be present on the TFTP server.Switch(config)# ip dhcp snooping database tftp://10.1.1.1/directory/fileThis example shows how to store a binding file called file01.txt in the stack master NVRAM:Switch(config)# ip dhcp snooping database flash:file01.txtYou can verify your settings by entering the show ip dhcp snooping database privileged EXECcommand.Related Commands Command Descriptionip dhcp snoopingEnables DHCP snooping on a VLAN.ip dhcp snooping binding Configures the DHCP snooping binding database.show ip dhcp snooping database Displays the status of DHCP snooping database agent.2-236Catalyst 3750-E and 3560-E Switch Command ReferenceOL-9776-08