Configuring Dhcp Features - Cisco Catalyst 3550 series Software Configuration Manual

Chapter 19

Configuring DHCP Features

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Configuring DHCP Features
These sections describe how to configure DHCP snooping and option 82 on your switch:
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Default DHCP Configuration
Table 19-1
Table 19-1 Default DHCP Configuration
Feature
DHCP snooping enabled globally
DHCP snooping information option
DHCP relay information option
DHCP snooping limit rate
DHCP snooping trust
DHCP snooping VLAN
DHCP Snooping Configuration Guidelines
These are the configuration guidelines for DHCP snooping.
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78-11194-09
The DHCP server unicasts the reply to the switch if the request was relayed to the server by the
switch. When the client and server are on the same subnet, the server broadcasts the reply. The
switch verifies that it originally inserted the option-82 data by inspecting the remote ID and possibly
the circuit ID fields. The switch removes the option-82 field and forwards the packet to the switch
port that connects to the DHCP client that sent the DHCP request.
Default DHCP Configuration, page 19-3
DHCP Snooping Configuration Guidelines, page 19-3
Upgrading from a Previous Software Release, page 19-4
Enabling DHCP Snooping and Option 82, page 19-4
Enabling the DHCP Relay Agent and Option 82, page 19-6
Validating the Relay Agent Information Option 82, page 19-6
Configuring the Reforwarding Policy, page 19-7
Specifying the Packet Forwarding Address, page 19-7
shows the default DHCP configuration.
You must globally enable DHCP snooping on the switch.
DHCP snooping is not active until DHCP snooping is enabled on a VLAN.
Default Setting
Disabled
Enabled
Enabled
None configured
Untrusted
Disabled
Catalyst 3550 Multilayer Switch Software Configuration Guide
Configuring DHCP Features
19-3