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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
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Chapter21 Configuring DHCP Feat ures and IP Source Guard Configuring DHCP Features
DHCP Snooping Configuration Guidelines
These are the configuration guidelines for DHCP snooping.
You must globally enable DHCP snooping on the switch.
DHCP snooping is not active until DHCP snooping is enabled on a VLAN.
Before globally enabling DHCP snooping on the switch, make sure that the devices acting as the
DHCP server and the DHCP relay agent are configured and enabled.
When you globally enable DHCP snooping on the switch, these Cisco IOS commands are not
available until snooping is disabled. If you enter these commands, the switch returns an error
message, and the configuration is not applied.
ip dhcp relay information check global configuration command
ip dhcp relay information policy global configuration command
ip dhcp relay information trust-all global configuration command
ip dhcp relay information trusted interface configuration command
Before configuring the DHCP snooping information option on your switch, be sure to configu re the
device that is acting as the DHCP server. For example, you must specify the IP addresses that the
DHCP server can assign or exclude, or you must configure DHCP options for the se d evices.
When configuring a large number of circuit IDs on a switch, consider the impact of lengthy character
strings on the NVRAM or the flash memory. If the circuit-ID configurations, combined with other
data, exceed the capacity of the NVRAM or the flash memory, an error message appears.
DHCP snooping option to accept packets on
untrusted input interfaces3Disabled
DHCP snooping limit rate None configured
DHCP snooping trust Untrusted
DHCP snooping VLAN Disabled
DHCP snooping MAC address verification Enabled
Cisco IOS DHCP server binding database 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.
DHCP snooping binding database agent Enabled in Cisco IOS software, requires
configuration. This feature is operational only
when a destination is configured.
1. The switch responds to DHCP requests only if it is configured as a DHCP server.
2. The switch relays DHCP packets only if the IP address of the DHCP server is configured on the SVI of the DHCP client.
3. Use this feature when the switch is an aggregation switch that receives packets with option-82 information from an edge
switch.
Table21-1 Default DHCP Configuration (continued)
Feature Default Setting