Configuring Dhcp Snooping - Cisco Catalyst 4500 Series Software Configuration Manual

Configuring DHCP Snooping

The values for these fields in the packets change from the default values when you configure the remote
ID and circuit ID suboptions:
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Figure 60-3
Circuit ID Suboption Frame Format (for user-configured string):
Suboption
type
1 byte
Remote ID Suboption Frame Format (for user-configured string):
Suboption
type
1 byte
Configuring DHCP Snooping
When you configure DHCP snooping on your switch, you are enabling the switch to differentiate
untrusted interfaces from trusted interfaces. You must enable DHCP snooping globally before you can
use DHCP snooping on a VLAN. You can enable DHCP snooping independently from other DHCP
features.
These sections describe how to configure DHCP snooping:
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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
60-6
Circuit ID suboption fields
The circuit ID type is 1.
–
The length values are variable, depending on the length of the string that you configure.
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Remote ID suboption fields
The remote ID type is 1.
–
The length values are variable, depending on the length of the string that you configure.
–
User-Configured Suboption Packet Formats
Circuit
ID type
Length Length
1 N+2 1 N ASCII Circuit ID string
1 byte 1 byte 1 byte
Remote
ID type
Length Length
2 N+2 1 N ASCII Remote ID string or hostname
1 byte 1 byte 1 byte
Default Configuration for DHCP Snooping, page 60-7
Enabling DHCP Snooping, page 60-7
Enabling DHCP Snooping on the Aggregation Switch, page 60-9
Enabling DHCP Snooping and Option 82, page 60-10
Enabling DHCP Snooping on Private VLAN, page 60-12
Configuring DHCP Snooping on Private VLAN, page 60-12
Chapter 60 Configuring DHCP Snooping, IP Source Guard, and IPSG for Static Hosts
N bytes (N = 3-63)
N bytes (N = 1-63)