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Cisco IOS Software Releases 12.2 T

UDP Forwarding Support of IP Redundancy Virtual Router Group

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Table Of Contents

UDP Forwarding Support of IP Redundancy Virtual Router Group

Finding Feature Information

Contents

Information About UDP Forwarding Support for IP Redundancy Virtual Router Groups

Benefits of the UDP Forwarding Support for Virtual Router Groups Feature

How to Configure UDP Forwarding Support for IP Redundancy Virtual Router Groups

Configuring UDP Forwarding Support for IP Redundancy Virtual Router Groups

Configuration Examples for UDP Forwarding Support for IP Redundancy Virtual Router Groups

Configuring UDP Forwarding Support for IP Redundancy Virtual Router Groups: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for UDP Forwarding Support for IP Redundancy Virtual Router Groups


UDP Forwarding Support of IP Redundancy Virtual Router Group

First Published: March 17, 2003
Last Updated: February 28, 2006

User Datagram Protocol (UDP) forwarding is a feature used in Cisco IOS software to forward broadcast and multicast packets received for a specific IP address. Virtual Router Group (VRG) support is currently implemented with the Hot Standby Routing Protocol (HSRP) and it allows a set of routers to be grouped as a logical router that answers to a well-known IP address. The UDP Forwarding Support for IP Redundancy Virtual Router Groups feature enables UDP forwarding to be VRG aware, resulting in forwarding only to the active router in the VRG.

Finding Feature Information

Your software release may not support all the features documented in this module. 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 UDP Forwarding Support for IP Redundancy Virtual Router Groups" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS XE 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

Information About UDP Forwarding Support for Virtual Router Group, page 2

How to Configure UDP Forwarding Support for Virtual Router Group, page 2

Additional References, page 3

Command Reference, page 4

Information About UDP Forwarding Support for IP Redundancy Virtual Router Groups

Before you configure the UDP Forwarding Support of Virtual Router Group feature, you should understand the following concepts:

•Benefits of the UDP Forwarding Support for Virtual Router Groups Feature

Benefits of the UDP Forwarding Support for Virtual Router Groups Feature

Forwarding is limited to the active router in the VRG instead of all routers within the VRG. Prior to the implementation of this feature the only VRG support was HSRP. Within a VRG that is formed by HSRP, the forwarding of UDP-based broadcast and multicast packets is done by all the routers within the VRG. This process can cause some DHCP servers to operate incorrectly. By making the UDP forwarding code VRG aware, forwarding will be limited to the active router in the VRG.

VRG awareness is achieved with IP Redundancy Service (IRS). The IRS API provides for notification updates of a specific VRG, addition and deletion of a VRG, and querying of the current state of a VRG. State change notification is provided to avoid the performance impact of querying the state of the VRG each time it is needed. The UDP forwarding code caches the VRG state for each required helper address defined. Each time the UDP forwarding code needs to execute, it checks the current state of the VRG associated with the helper address and forwards only for VRGs that are active.

Note The UDP Forwarding Support for virtual Router Groups feature is available only on platforms that support VRGs.

How to Configure UDP Forwarding Support for IP Redundancy Virtual Router Groups

This section contains the following procedure:

•Configuring UDP Forwarding Support for IP Redundancy Virtual Router Groups

Configuring UDP Forwarding Support for IP Redundancy Virtual Router Groups

Perform this task to configure UDP Forwarding Support for IP Redundancy Virtual Router Groups.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number

4. ip helper-address address redundancy vrg-name

5. end

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 

interface type number

Example:

Router(config)# interface fastethernet 0/0

Specifies an interface and enters interface configuration mode.

Step 4 

ip helper-address address redundancy vrg-name

Example:

Router(config-if)# ip helper-address 10.1.1.1 redundancy shop

Enables UDP forwarding support for the VRG.

Step 5 

end

Example:

Router(config-if)# end

Exits the current configuration mode and returns to privileged EXEC mode.

Configuration Examples for UDP Forwarding Support for IP Redundancy Virtual Router Groups

This section provides the following configuration example:

•Configuring UDP Forwarding Support for IP Redundancy Virtual Router Groups: Example

Configuring UDP Forwarding Support for IP Redundancy Virtual Router Groups: Example

The following example shows how to configure UDP Forwarding Support for IP Redundancy Virtual Router Groups: 

interface fastethernet 0/0

 no shutdown

 ip address 172.16.10.1 255.255.255.0

 ip helper-address 10.1.1.1 redundancy shop


Additional References

The following sections provide references related to the UDP Forwarding Support for IP Redundancy Virtual Router Groups feature.

Related Documents

Related Topic
Document Title

IP application services commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples

Cisco IOS IP Application Services Command Reference


Standards

Standard
Title

No new or modified standards are supported, and support for existing standards has not been modified

—


MIBs

MIB
MIBs Link

No new or modified MIBs are supported, and support for existing MIBs has not been modified

—


RFCs

RFC
Title

No new or modified RFCs are supported, and support for existing RFCs has not been modified

—


Technical Assistance

Description
Link

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Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport


Feature Information for UDP Forwarding Support for IP Redundancy Virtual Router Groups

Table 1 lists the features in this module. For information on a feature in this technology that is not documented here, see the other available documentation for your Cisco IOS release.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS, Catalyst OS and Cisco IOS XE 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 Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Table 1 Feature Information for UDP Forwarding Support for IP Redundancy Virtual Router Groups

Feature Name
Releases
Feature Information

UDP Forwarding Support for IP Redundancy Virtual Router Group

12.2(15)T

User Datagram Protocol (UDP) forwarding is a feature used in Cisco IOS software to forward broadcast and multicast packets received for a specific IP address. Virtual Router Group (VRG) support is currently implemented with the Hot Standby Routing Protocol (HSRP) and it allows a set of routers to be grouped as a logical router that answers to a well known well-known IP address. The UDP Forwarding Support for IP Redundancy Virtual Router Groups feature enables UDP forwarding to be VRG aware, resulting in forwarding only to the active router in the VRG.

The following command was introduced or modified: ip helper-address.


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

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