Cisco Catalyst 2960 Series, Configuration Manual

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• The following prerequisites apply to DHCP snooping binding database configuration:
◦ You must configure a destination on the DHCP snooping binding database to use the switch for
DHCP snooping.
◦ Because both NVRAM and the flash memory have limited storage capacity, we recommend that
you store the binding file on a TFTP server.
◦ For network-based URLs (such as TFTP and FTP), you must create an empty file at the configured
URL before the switch can write bindings to the binding file at that URL. See the documentation
for your TFTP server to determine whether you must first create an empty file on the server; some
TFTP servers cannot be configured this way.
◦ To ensure that the lease time in the database is accurate, we recommend that you enable and
configure Network Time Protocol (NTP).
◦ If NTP is configured, the switch writes binding changes to the binding file only when the switch
system clock is synchronized with NTP.
• Before configuring the DHCP relay agent on your switch, make sure to configure the device that is
acting as the DHCP server. You must specify the IP addresses that the DHCP server can assign or
exclude, configure DHCP options for devices, or set up the DHCP database agent.
• If you want the switch to relay DHCP packets, the IP address of the DHCP server must be configured
on the switch virtual interface (SVI) of the DHCP client.
• If a switch port is connected to a DHCP server, configure a port as trusted by entering the ip dhcp
snooping trust interface configuration command.
• If a switch port is connected to a DHCP client, configure a port as untrusted by entering the no ip dhcp
snooping trust interface configuration command.
Related Topics
DHCP Snooping, on page 1266
Enabling DHCP Snooping and Option 82
Follow these steps to enable DHCP snooping on the switch:
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
1278
How to Configure DHCP Features