Dhcp Snooping Configuration Guidelines - Cisco Catalyst 2960 series Configuration Manual

Feature
Cisco IOS DHCP server binding database
DHCP snooping binding database agent
12 The switch responds to DHCP requests only if it is configured as a DHCP server.
13 The switch relays DHCP packets only if the IP address of the DHCP server is configured on the SVI of the DHCP client.
14 Use this feature when the switch is an aggregation switch that receives packets with option-82 information from an edge switch.

DHCP Snooping Configuration Guidelines

• 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.
• You can display DHCP snooping statistics by entering the show ip dhcp snooping statistics user EXEC
command, and you can clear the snooping statistics counters by entering the clear ip dhcp snooping
statistics privileged EXEC command.
Configuring the DHCP Server
The switch can act as a DHCP server.
For procedures to configure the switch as a DHCP server, see the "Configuring DHCP" section of the "IP
addressing and Services" section of the Cisco IOS IP Configuration Guide, Release 12.4.
DHCP Server and Switch Stacks
The DHCP binding database is managed on the stack master. When a new stack master is assigned, the new
master downloads the saved binding database from the TFTP server. If the stack master fails, all unsaved
bindings are lost. The IP addresses associated with the lost bindings are released. You should configure an
automatic backup by using the ip dhcp database url [timeout seconds | write-delay seconds] global
configuration command.
When a stack merge occurs, the stack master that becomes a stack member loses all of the DHCP lease
bindings. With a stack partition, the new master in the partition acts as a new DHCP server without any of
the existing DHCP lease bindings.
Configuring the DHCP Relay Agent
Follow these steps to enable the DHCP relay agent on the switch:
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
How to Configure DHCP Features
Default Setting
Enabled in Cisco IOS software, requires configuration.
Note The switch gets network addresses and
configuration parameters only from a device
configured as a DHCP server.
Enabled in Cisco IOS software, requires configuration.
This feature is operational only when a destination is
configured.
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