Cisco IOS IP Addressing Services Configuration Guide, Release 12.2SR - DHCP Option 82 Configurable Circuit ID and Remote ID [Cisco IOS Software Releases 12.2 SR]

Table Of Contents

DHCP Option 82 Configurable Circuit ID and Remote ID

Finding Feature Information

Contents

Restrictions for DHCP Option 82 Configurable Circuit ID and Remote ID

Information About DHCP Option 82 Configurable Circuit ID and Remote ID

How to Configure DHCP Option 82 Configurable Circuit ID and Remote ID

Configuring DHCP Snooping on Private VLANs

Configuration Example for DHCP Option 82 Configurable Circuit ID and Remote ID

Mapping Private-VLAN Associations: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for DHCP Option 82 Configurable Circuit ID and Remote ID

DHCP Option 82 Configurable Circuit ID and Remote ID

First Published: February 26, 2009

Last Updated: February 26, 2009

The Cisco DHCP Option 82 Configurable Circuit ID and Remote ID provides more naming choices in the Option 82 Remote ID and Option 82 Circuit ID suboptions. For example, you can use a switch-configured hostname or specify an ASCII text string for the remote ID, and you can configure an ASCII text string to override the circuit ID.

Note Refer to the configuration guide for your platform for information about configuring Dynamic Host Configuration Protocol (DHCP). See the "Configuring DHCP Snooping" section of the Cisco 7600 Series Cisco IOS Software Configuration Guide, Release 12.2SR, for information about configuring DHCP on Cisco 7600 series routers. See the "Related Documents" section for sources of information about configuring DHCP on other Cisco platforms.

Finding Feature Information

For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for DHCP Option 82 Configurable Circuit ID and Remote ID" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Restrictions for DHCP Option 82 Configurable Circuit ID and Remote ID

•Information About DHCP Option 82 Configurable Circuit ID and Remote ID

•How to Configure DHCP Option 82 Configurable Circuit ID and Remote ID

•Configuration Example for DHCP Option 82 Configurable Circuit ID and Remote ID

•Additional References

•Feature Information for DHCP Option 82 Configurable Circuit ID and Remote ID

Restrictions for DHCP Option 82 Configurable Circuit ID and Remote ID

When DHCP snooping is configured on a primary VLAN, you cannot configure snooping with different settings on any of its secondary VLANs. You must configure DHCP snooping for all associated VLANs on the primary VLAN. If DHCP snooping is not configured on the primary VLAN and you try to configure it on the secondary VLAN, for example, VLAN 200, this message appears:
2w5d:%DHCP_SNOOPING-4-DHCP_SNOOPING_PVLAN_WARNING:DHCP Snooping configuration may not 
take effect on secondary vlan 200. DHCP Snooping configuration on secondary vlan is 
derived from its primary vlan.
You can use the show ip dhcp snooping command to display all VLANs, both primary and secondary, that have DHCP snooping enabled.

Information About DHCP Option 82 Configurable Circuit ID and Remote ID

The DHCP Option 82 Configurable Circuit ID and Remote ID feature enhances validation security by allowing you to determine what information is provided in the Option 82 Remote ID and Option 82 Circuit ID suboptions.

You can enable DHCP snooping on private VLANs. When DHCP snooping is enabled, the configuration is propagated to both a primary VLAN and its associated secondary VLANs. When DHCP snooping is enabled on a primary VLAN, it is also enabled on its secondary VLANs.

See the "DHCP Snooping Option-82 Data Insertion" section of the Cisco 7600 Series Cisco IOS Software Configuration Guide for information about using DHCP to centrally manage the IP address assignments for a large number of subscribers in residential, metropolitan Ethernet-access environments.

Figure 1 shows the packet format used when DHCP snooping is globally enabled and the ip dhcp snooping information option global configuration command is entered with the Circuit ID suboption.

Figure 1 Suboption Packet Formats, Circuit ID Specified

Figure 2 shows the packet format used when DHCP snooping is globally enabled and the ip dhcp snooping information option global configuration command is entered with the Remote ID suboption.

Figure 2 Suboption Packet Formats, Remote ID Specified

How to Configure DHCP Option 82 Configurable Circuit ID and Remote ID

This section contains the following task:

•Configuring DHCP Snooping on Private VLANs

Configuring DHCP Snooping on Private VLANs

Perform these tasks to configure DHCP snooping on private primary and secondary VLANs:

•Configure a private, primary VLAN.

•Associate with it an isolated VLAN.

•Create an SVI interface for the primary VLAN, and associate it with the appropriate loopback IP and helper address.

•Enable DHCP snooping on the primary VLAN, which also enables it on the associated VLAN.

Note You must also configure a server to assign the IP address, a DHCP pool, and a relay route so that snooping can be effective.

SUMMARY STEPS

1. enable

2. configure terminal

3. vlan vlan-id

4. private-vlan primary

5. private-vlan association associated-vlan-list

6. configure terminal

7. vlan vlan-id

8. private-vlan isolated

9. configure terminal

10. interface vlan primary-vlan-id

11. ip unnumbered loopback

12. private-vlan mapping [secondary-vlan-list | add secondary-vlan-list | remove secondary-vlan-list]

13. configure terminal

14. ip dhcp snooping vlan primary-vlan-id

DETAILED STEPS

Command or Action

Purpose

Step 1

enable
Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 3

vlan vlan-id
Example:

Router(config)# vlan 70

Enters VLAN configuration submode for the named private VLAN.

Step 4

private-vlan primary
Example:

Router(config-vlan)# private-vlan primary

Designates the VLAN as the primary private VLAN.

Step 5

private-vlan association secondary-vlan-list
Example:

Router(config-vlan)# private-vlan association 7

Configures private VLANs (PVLANs) and the association between a PVLAN and a secondary VLAN.

Step 6

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 7

vlan vlan_ID
Example:

Router(config)# vlan 7

Enters VLAN configuration mode for the named private VLAN.

•In this example, the associated secondary VLAN, vlan 7.

Step 8

private-vlan isolated
Example:

Router(config-vlan)# private-vlan isolated

Designates the VLAN as an isolated private VLAN.

Step 9

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 10

interface vlan primary-vlan_id
Example:

Router(config)# interface vlan 70

Creates a dynamic Switch Virtual Interface (SVI) on the primary VLAN.

Step 11

ip unnumbered loopback
Example:

Router(config)# ip unnumbered loopback1

Specifies IP unnumbered loopback.

Step 12

private-vlan mapping [secondary-vlan-list | add secondary-vlan-list | remove secondary-vlan-list]
Example:

Router(config-vlan)# private-vlan mapping 7

Creates a mapping between the primary and the secondary VLANs so that they share the same primary VLAN SVI.

Step 13

configure terminal
Example:

Router# configure terminal

Enters global configuration mode.

Step 14

ip dhcp snooping vlan primary-vlan_id
Example:

Router(config)# ip dhcp snooping vlan 70

Enables DHCP snooping on the primary and associated VLANs.

Configuration Example for DHCP Option 82 Configurable Circuit ID and Remote ID

This section provides the following configuration example:

•Mapping Private-VLAN Associations: Example

Mapping Private-VLAN Associations: Example

The following interface configuration example shows how to map the private-VLAN associations. The user-configurable circuit ID "aabb11" is inserted on the secondary VLAN, vlan 7.
interface GigabitEthernet9/0/1
switchport
switchport private-vlan host-association 70 7
switchport mode private-vlan host
no mls qos trust
spanning-tree portfast
ip dhcp snooping vlan 7 information option format-type circuit-id string aabb11
The following example shows how to define a DHCP class "C1" and specify the hex string of the corresponding class at the server by using the hex string that matches the circuit-ID value entered in the interface configuration example. That is, the hex string 00000000000000000000000000000006616162623131 mask fffffffffffffffffffffffffffffff0000000000000 matches the circuit ID aabb11.
ip dhcp class C1
relay agent information
relay-information hex 00000000000000000000000000000006616162623131 mask 
fffffffffffffffffffffffffffffff0000000000000
Additional References

Related Documents

Related Topic

Document Title

Configuring DHCP on the Cisco 7600 series router

"Configuring DHCP Snooping" section of the Cisco 7600 Series Cisco IOS Software Configuration Guide

Configuring DHCP on the Cisco Catalyst 3550 multilayer switch

"Configuring DHCP Features" section of the Catalyst 3550 Multilayer Switch Software Configuration Guide

Configuring DHCP on the Cisco Catalyst 2970 switch

"Configuring DHCP Features" section of the Catalyst 2970 Switch Software Configuration Guide

Configuring DHCP on the Cisco Catalyst 3560 switch

"Configuring DHCP Features and IP Source Guard" section of the Catalyst 3560 Switch Software Configuration Guide

Configuring DHCP on the Cisco Catalyst 3750 switch

"Configuring DHCP Features and IP Source Guard" section of the Catalyst 3750 Switch Software Configuration Guide

DHCP commands: complete command syntax, command mode command history, defaults, usage guidelines, and examples

Cisco IOS IP Addressing Services Command Reference

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—

MIBs

MIB

MIBs Link

•

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for DHCP Option 82 Configurable Circuit ID and Remote ID

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Table 1 Feature Information for DHCP Option 82 Configurable Circuit ID and Remote ID

Feature Name

Releases

Feature Information

DHCP Option 82 Configurable Circuit ID and Remote ID

12.2(33)SRD1

Provides naming choices in the Option 82 Remote ID and Option 82 Circuit ID suboptions.

The following commands were introduced or modified: ip dhcp snooping vlan.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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