DHCP Snooping and Switch Stacks
DHCP snooping is managed on the stack master. When a new switch joins the stack, the switch receives the
DHCP snooping configuration from the stack master. When a member leaves the stack, all DHCP snooping
address bindings associated with the switch age out.
All snooping statistics are generated on the stack master. If a new stack master is elected, the statistics counters
reset.
When a stack merge occurs, all DHCP snooping bindings in the stack master are lost if it is no longer the
stack master. With a stack partition, the existing stack master is unchanged, and the bindings belonging to the
partitioned switches age out. The new master of the partitioned stack begins processing the new incoming
DHCP packets.
How to Configure DHCP Features
Default DHCP Snooping Configuration
Table 19: Default DHCP Configuration
Default Setting
Feature
Enabled in Cisco IOS software, requires configuration
DHCP server
Enabled
DHCP relay agent
None configured
DHCP packet forwarding address
Enabled (invalid messages are dropped)
Checking the relay agent information
Replace the existing relay agent information
DHCP relay agent forwarding policy
Disabled
DHCP snooping enabled globally
Enabled
DHCP snooping information option
Disabled
DHCP snooping option to accept packets on untrusted
input interfaces
None configured
DHCP snooping limit rate
Untrusted
DHCP snooping trust
Disabled
DHCP snooping VLAN
Enabled
DHCP snooping MAC address verification
Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
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Configuring DHCP
DHCP Snooping and Switch Stacks