Cisco WS-C3560E-48PD-SF Command Reference - Page 176

ip dhcp snooping database Chapter 2 Catalyst 3560 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: • NTP authentication • NTP peer and server associations • NTP broadcast service • NTP access restrictions • NTP packet source IP address 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:/filename command to save the DHCP snooping binding database in the 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 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 Description Enables DHCP snooping on a VLAN. Configures the DHCP snooping binding database. Displays the status of DHCP snooping database agent. 2-144 Catalyst 3560 Switch Command Reference 78-16405-05