ISDN Backup in MPLS Core

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Updated:March 29, 2005

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ISDN Backup in MPLS Core

Table Of Contents

ISDN Backup in MPLS Core

Contents

Prerequisites for ISDN Backup in MPLS Core

Restrictions for ISDN Backup in MPLS Core

Information About ISDN Backup in MPLS Core

How ISDN Backup in MPLS Core Works

Benefits of ISDN Backup in MPLS Core Feature

How to Configure ISDN Backup in MPLS Core

Configuring Primary Interface for Backup

Configuring the Dialer Profile as Backup Interface

Verifying the ISDN Backup for MPLS Feature

Configuration Examples for ISDN Backup in MPLS Core

ISDN Backup for MPLS Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

Glossary


ISDN Backup in MPLS Core

When a primary link is down in the Multiprotocol Label Switching (MPLS) core network, the ISDN Backup in MPLS Core feature allows a backup ISDN link on a dialer interface to be brought up to restore network connectivity. This feature ensures high availability of the link between two routers in the MPLS core by providing a backup mechanism.

Feature Specifications for the ISDN Backup in MPLS Core feature

Feature History
 
Release
Modification

12.3(2)T

This feature was introduced.

12.2(27)SBA

This feature was integrated into Cisco IOS Release 12.2(27)SBA.


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Contents

•Prerequisites for ISDN Backup in MPLS Core

•Restrictions for ISDN Backup in MPLS Core

•Information About ISDN Backup in MPLS Core

•How to Configure ISDN Backup in MPLS Core

•Configuration Examples for ISDN Backup in MPLS Core

•Additional References

•Command Reference

•Glossary

Prerequisites for ISDN Backup in MPLS Core

You need to first configure the Dialer Persistent feature.

Restrictions for ISDN Backup in MPLS Core

•The ISDN Backup in MPLS Core feature works only with dialer profile configuration.

•The ISDN Backup in MPLS Core feature is available only for PPP encapsulation.

Information About ISDN Backup in MPLS Core

Before configuring and implementing the ISDN Backup for MPLS Core feature, you should understand the following concepts:

•How ISDN Backup in MPLS Core Works

•Benefits of ISDN Backup in MPLS Core Feature

How ISDN Backup in MPLS Core Works

The dialer profile interface is configured as backup to the primary interface. The dialer interface should have the Dialer Persistent feature configured and MPLS IP should be enabled with encapsulation PPP. For more information on the Dialer Persistent feature refer to the Cisco IOS Dial Technologies Configuration Guide, Release 12.3.

When the primary interface goes down, the dialer profile that is acting as the backup will bring up the backup interface without waiting for any interesting traffic because Dialer Persistent has been configured. Once the link to the destination is established, tagged packets will flow via the dialer interface.

Benefits of ISDN Backup in MPLS Core Feature

The ISDN Backup in MPLS Core feature provides MPLS switching support on dialer interfaces for ISDN backup in MPLS core networks. When you configure a backup ISDN link on a dialer interface, the dialer interface can be brought up to restore network connectivity when a primary link goes down in an MPLS core network.

How to Configure ISDN Backup in MPLS Core

This section contains the following procedures:

•Configuring Primary Interface for Backup

•Configuring the Dialer Profile as Backup Interface

•Verifying the ISDN Backup for MPLS Feature

Configuring Primary Interface for Backup

Perform this task to configure a primary interface backup.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type slot/port.subinterface-number [multipoint | point-to-point]

4. backup interface dialer number

5. exit

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 slot/port.subinterface-number [multipoint | point-to-point]

Example:

Router(config)# interface serial 1

Configures an interface type and enters interface configuration mode.

Step 4 

backup interface dialer number

Example:

Router(config-if)# backup interface dialer 1

Configures an interface as a secondary or dial backup interface.

Step 5 

exit

Example:

Router(config-if)# exit

Returns to global configuration mode.

Configuring the Dialer Profile as Backup Interface

Perform this task to configure the Dialer Persistent feature on the backup interface.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface dialer number

4. encapsulation type

5. dialer persistent [delay [initial] seconds | max-attempts number]

6. tag-switching ip (interface configuration)

7. exit

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 dialer number

Example:

Router(config)# interface dialer 1

Creates a dialer interface and enters interface configuration mode.

Step 4 

encapsulation type

Example:

Router(config-if)# encapsulation ppp

Specifies the encapsulation type.

Step 5 

dialer persistent [delay [initial] seconds | max-attempts number]

Example:

Router(config-if)# dialer persistent delay initial 20

Forces a dialer interface to be connected at all times, even in the absence of interesting traffic.

Step 6 

tag-switching ip

Example:

Router(config-if)# tag-switching ip

Enables label switching of IPv4 packets on an interface.

Step 7 

exit

Example:

Router(config-if)# exit

Returns to global configuration mode.

Verifying the ISDN Backup for MPLS Feature

Perform this task to verify that you have correctly configured the ISDN Backup for MPLS feature.

SUMMARY STEPS

1. enable

2. show mpls forwarding-table

3. show mpls interfaces [interface] [detail]

4. exit

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

show mpls forwarding-table

Example:

Router# show mpls forwarding-table

Displays the contents of the MPLS FIB.

Step 3 

show mpls interfaces [interface] [detail]

Example:

Router(config)# show mpls interfaces dialer detail

Displays the contents of the Multiprotocol Label Switching (MPLS) label forwarding information base (LFIB).

Step 4 

exit

Example:

Router(config)# exit

Returns to global configuration mode.

Configuration Examples for ISDN Backup in MPLS Core

This section provides the following configuration example:

•ISDN Backup for MPLS Example

ISDN Backup for MPLS Example

The following example shows the interface Dialer 1 being configured as the backup interface. 

interface Serial1

 backup interface Dialer1

 ip address 172.16.1.1 255.0.0.0

 mpls ip

 encapsulation ppp 

! 

interface Serial0:23

 no ip address

 encapsulation ppp

 dialer pool-member 1

 ppp authentication chap

!

interface Dialer1

 ip address 172.16.1.3 255.0.0.0

 encapsulation ppp

 dialer pool 1

 dialer remote-name P1

 dialer string 1114

 dialer persistent 

 dialer-group 1

 mpls ip

 ppp authentication chap

!

Additional References

The following sections provide additional references related to the ISDN Backup in MPLS Core feature.

Related Documents

Related Topic
Document Title

Configuring the Dialer Persistent feature

"Dialer Persistent Feature", Release 12.2(4)T

Configuring the Dial Backup feature

"Configuring Dial Backup with Dialer Profiles" chapter of the Cisco IOS Dial Technologies Configuration Guide, Release 12.2 T


Standards

Standards
Title

None

—


MIBs

MIBs
MIBs Link

None

To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml


RFCs

RFCs
Title

None

—


Technical Assistance

Description
Link

Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/public/support/tac/home.shtml


Command Reference

None.

Glossary

Note Refer to the Internetworking Terms and Acronyms for terms not included in this glossary.

Copyright © 2003-2005 Cisco Systems, Inc. All rights reserved.

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