CLI Reference Guide-R04

Chapter 9 | General Security Measures
DHCPv4 Snooping
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VLAN according to the default status, or as specifically configured for an
interface with the no ip dhcp snooping trust command.
◆ When an untrusted port is changed to a trusted port, all the dynamic DHCP
snooping bindings associated with this port are removed.
◆ Additional considerations when the switch itself is a DHCP client – The port(s)
through which it submits a client request to the DHCP server must be
configured as trusted.
Example
This example sets port 5 to untrusted.
Console(config)#interface ethernet 1/5
Console(config-if)#no ip dhcp snooping trust
Console(config-if)#
Related Commands
ip dhcp snooping (325)
ip dhcp snooping vlan (333)
ip dhcp snooping
vlan-flooding
This command configures the specified interface to forward DHCP packets when
DHCP snooping is disabled on the VLAN. Use the no form to block DHCP packets
when DHCP snooping is disabled on the VLAN.
Syntax
[no] ip dhcp snooping vlan-flooding
Default Setting
Enabled
Command Mode
Interface Configuration (Ethernet, Port Channel)
Command Usage
◆ When DHCP snooping is enabled on a VLAN, the port will forward DHCP
packets to a trusted interface.
◆ When DHCP snooping is disabled on a VLAN, the port will block DHCP packets
when VLAN flooding is disabled and forward packets when VLAN flooding is
enabled.