
60-6
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 60 Configuring DHCP Snooping, IP Source Guard, and IPSG for Static Hosts
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:
•
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.
•
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.
Figure 60-3
User-Configured Suboption Packet Formats
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:
•
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
Length
Length
Circuit
ID type
Suboption
type
Circuit ID
S
uboption Frame Format (for user-configured string):
Remote ID
S
uboption Frame Format (for user-configured string):
Suboption
type
Length
Length
Remote
ID type
145774
N
1
N+2
1
N
1
N+2
2
ASCII Circuit ID string
1 byte 1 byte 1 byte
N bytes (
N = 3-63)
ASCII Remote ID string or hostname
N bytes (
N = 1-63)
1 byte
1 byte 1 byte 1 byte
1 byte
Содержание Catalyst 4500 Series
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