Chapter 19: Configuring Dhcp; Dhcp Snooping - Cisco 500 series Administration Manual

Configuring DHCP

DHCP Snooping

Cisco 500 Series Stackable Managed Switch Administration Guide
This section describes how the DHCP Relay and Snooping features are
implemented on the switch.
The following topics are covers in this section:
• DHCP Snooping
• DHCP Relay
• Option 82
• Interactions Between DHCP Snooping, DHCP Relay and Option 82
• DHCP Snooping Binding Database
• DHCP Configuration
DHCP snooping provides a security mechanism to prevent receiving false DHCP
response packets and to log DHCP addresses. It does this by treating ports on the
switch as either trusted or untrusted.
A trusted port is a port that is connected to a DHCP server and is allowed to
assign DHCP addresses. DHCP messages received on trusted ports are allowed
to pass through the switch.
An untrusted port is a port that is not allowed to assign DHCP addresses. By
default, all ports are considered untrusted until you declare them trusted (in the
DHCP Snooping Interface Settings page).
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