Multilink PPP Minimum Links Mandatory

First Published: 12.1(11b)E
Last Updated: February 28, 2006

Multilink PPP allows multiple PPP links to be established in parallel to the same destination. Multilink PPP is often used with dialup lines or ISDN connections to easily increase the amount of bandwidth between points.

With the introduction of the Multilink PPP Minimum Links Mandatory feature, you can configure the minimum number of links in a Multilink PPP (MLP) bundle required to keep that bundle active by entering the ppp multilink min-links links mandatory command. When you configure this command, all Network Control Protocols (NCPs) for an MLP bundle are disabled until the MLP bundle has the required minimum number of links. When a new link is added to the MLP bundle that brings the number of links up to the required minimum number of links, the NCPs are activated for the MLP bundle. When a link is removed from an MLP bundle, and the number of links falls below the required minimum number of links for that MLP bundle, the NCPs are disabled for that MLP bundle.

History for the Multilink PPP Minimum Links Mandatory Feature

Release
Modification

12.1(11b)E

This feature was introduced.

12.2(13)T

This feature was integrated into Cisco IOS Release 12.2(13)T.

12.2(14)S

This feature was integrated into Cisco IOS Release 12.2(14)S.

12.2(15)B

This feature was integrated into Cisco IOS Release 12.2(15)B and support for the Cisco 7401ASR and the Cisco 6400 series was added.

12.2(28)SB

This feature was integrated into Cisco IOS Release 12.2(28)SB.


This documentation describes the Multilink PPP Minimum Links Mandatory feature for Cisco IOS Releases 12.2(13)T, 12.2(14)S, and 12.2(15)B.

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Contents

•Information About Multilink PPP Minimum Links Mandatory

•How to Configure Multilink PPP Minimum Links Mandatory

•Configuration Examples for Multilink PPP Minimum Links Mandatory

•Additional References

•Command Reference

Information About Multilink PPP Minimum Links Mandatory

You must understand the following concepts to configure this feature:

•PPP Encapsulation Overview

•Multilink PPP Overview

PPP Encapsulation Overview

PPP, described in RFC 1661, encapsulates network layer protocol information over point-to-point links. You can configure PPP on the following types of physical interfaces:

•Asynchronous serial

•High-Speed Serial Interface (HSSI)

•ISDN

•Synchronous serial

When PPP encapsulation is enabled on physical interfaces, PPP can also be in effect on calls placed by the dialer interfaces that use the physical interfaces.

PPP supports option 3, authentication using Challenge Handshake Authentication Protocol (CHAP) or Password Authentication Protocol (PAP); option 4, Link Quality Monitoring (LQM); and option 5, Magic Number configuration options. Cisco IOS software always sends option 5 and negotiates for options 3 and 4 if so configured. All other options are rejected.

Magic Number support is available on all serial interfaces. PPP always attempts to negotiate for Magic Numbers, which are used to detect looped-back lines. Depending on how the down-when-looped command is configured, the router might shut down a link if it detects a loop.

Cisco IOS software provides the CHAP and PAP on serial interfaces running PPP encapsulation. For detailed information about authentication, refer to the Cisco IOS Security Configuration Guide.

Multilink PPP Overview

The Multilink PPP feature provides load balancing functionality over multiple WAN links, while providing multivendor interoperability, packet fragmentation and proper sequencing, and load calculation on both inbound and outbound traffic. The Cisco implementation of MLP supports the fragmentation and packet sequencing specifications in RFC 1990. Additionally, you can change the default endpoint discriminator value that is supplied as part of user authentication. Refer to RFC 1990 for more information about the endpoint discriminator.

MLP allows packets to be fragmented and the fragments to be sent at the same time over multiple point-to-point links to the same remote address. The multiple links come up in response to a defined dialer load threshold. The load can be calculated on inbound traffic, outbound traffic, or on either, as needed for the traffic between the specific sites. MLP provides bandwidth on demand and reduces transmission latency across WAN links.

MLP is designed to work over synchronous and asynchronous serial and BRI and PRI types of single or multiple interfaces that have been configured to support both dial-on-demand rotary groups and PPP encapsulation.

How to Configure Multilink PPP Minimum Links Mandatory

This section contains the following procedures:

•Configuring PPP (required)

•Configuring Multilink PPP (required)

•Configuring Multilink PPP Minimum Links Mandatory (required)

Configuring PPP

Perform this task to configure PPP.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type slot/port

4. encapsulation ppp

5. ppp authentication {chap | chap pap | pap chap | pap} [if-needed] [list-name | default] [callin]

6. exit

7. username name password secret

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

Example:

Router(config)# interface serial 1/0

Configures an interface and enters interface configuration mode.

•type—Type of interface to be configured.

•slot—Number of the slot being configured.

•port—Number of the port being configured.

Note Refer to the appropriate hardware manual for slot and port information.

Step 4 

encapsulation ppp

Example:

Router(config-if)# encapsulation ppp

Enables PPP encapsulation.

Step 5 

ppp authentication {chap | chap pap | pap chap | pap} [if-needed] [list-name | default] [callin]

Example:

Router(config-if)# ppp authentication chap

(Optional) Defines the authentication methods supported and the order in which they are used.

•chap—Enables CHAP on a serial interface.

•chap pap—Enables CHAP and PAP on a serial interface and configures CHAP to be used first.

•pap chap—Enables CHAP and PAP on a serial interface and configures PAP to be used first.

•pap—Enables PAP on a serial interface.

•if-needed—(Optional) Used with TACACS and extended TACACS. Does not perform CHAP or PAP authentication if the user has already provided authentication. This option is available only on asynchronous interfaces.

•list-name—(Optional) Used with authentication, authorization, and accounting (AAA). Specifies the name of a list of methods of authentication to use. If no list name is specified, the system uses the default. The list is created with the aaa authentication ppp command.

•default—(Optional) The name of the method list is created with the aaa authentication ppp command.

•callin—(Optional) Specifies authentication on incoming (received) calls only.

Step 6 

exit

Example:

Router(config-if)# exit

Exits interface configuration mode.

Step 7 

username name password secret

Example:

Router(config)# username username1 password password1

(Optional) Specifies the password to be used in CHAP or PAP caller identification.

•name—Assigns a host name, server name, user ID, or command name. The name argument can be only a single word and not more than one word. Blank spaces and quotation marks are not allowed.

•secret—Specifies the secret for the local router or the remote device. The secret is encrypted when it is stored on the local router. The secret can consist of any string of up to 11 ASCII characters. There is no limit to the number of username and password combinations that can be specified, allowing any number of remote devices to be authenticated.

Configuring Multilink PPP

Perform this task to configure MLP.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface multilink group-number

4. ip address address

5. encapsulation ppp

6. ppp multilink

7. ppp multilink max-links links

8. ppp multilink min-links links

9. bridge-group bridge-group-number

10. no shutdown

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 multilink group-number

Example:

Router(config)# interface multilink 3

Creates a multilink bundle and enters interface configuration mode.

•group-number—Specifies the number of the multilink bundle. Valid range is from 1 to 214748364.

Step 4 

ip address address

Example:

Router(config-if)# ip address 172.16.0.0

Assigns an IP address to the interface.

Step 5 

encapsulation ppp

Example:

Router(config-if)# encapsulation ppp

Enables PPP encapsulation.

Step 6 

ppp multilink

Example:

Router(config-if)# ppp multilink

Enables MLP.

Step 7 

ppp multilink max-links links

Example:

Router(config-if)# ppp multilink max-links 100

(Optional) Limits the maximum number of links that MLP can dial for dynamic allocation.

•links—Maximum number of links, in the range 0 to 255.

Step 8 

ppp multilink min-links links

Example:

Router(config-if)# ppp multilink min-links 5

(Optional) Specifies the preferred minimum number of links in an MLP bundle.

•links—Minimum number of links, in the range from 0 to 255.

Step 9 

bridge-group bridge-group-number

Example:

Router(config-if)# bridge-group 2

(Optional) Specifies the bridge group to which this interface belongs.

•bridge-group-number—Number of the bridge group to which the interface belongs. Valid values are from 1 to 255.

Note Use this command only if bridging is enabled for this interface.

Step 10 

no shutdown

Example:

Router(config-if)# no shutdown

Enables the interface.

Configuring Multilink PPP Minimum Links Mandatory

Perform this task to configure the minimum number of links in an MLP bundle required to keep that bundle active.

SUMMARY STEPS

1. enable

2. configure terminal

3. ppp multilink

4. ppp multilink min-links links mandatory

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 

ppp multilink

Example:

Router(config-if)# ppp multilink

Enables MLP.

Step 4 

ppp multilink min-links links mandatory

Example:

Router(config-if)# ppp multilink min-links 5 mandatory

Specifies the required minimum number of links in a Multilink PPP (MLP) bundle.

•If the minimum number of links in the MLP bundle falls below the number specified by the links argument, the MLP bundle is disabled.

•links—Minimum number of links, in the range from 0 to 255.

Verifying the Multilink PPP Minimum Links Mandatory Configuration

Perform this task to verify configuration of the Multilink PPP Minimum Links Mandatory feature.

SUMMARY STEPS

1. enable

2. show running-config [interface type number] [linenum]

3. show interfaces multilink group-number

4. show ppp multilink

5. show interfaces multilink group-number stat

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2 

show running-config [interface type number] [linenum]

Example:

Router# show running-config

Displays the contents of the currently running configuration file or the configuration for a specific interface, or map class information.

Step 3 

show interfaces multilink group-number

Example:

Router# show interfaces multilink 3

(Optional) Displays statistics for the specified multilink bundle.

Step 4 

show ppp multilink

Example:

Router# show ppp multilink

(Optional) Displays information about all existing multilink bundles and their member links.

Step 5 

show interfaces multilink group-number stat

Example:

Router# show interfaces multilink 3 stat

(Optional) Displays traffic statistics for a multilink bundle.

Examples

The following is sample output from the show running-config command that shows that the Multilink PPP Minimum Links Mandatory feature is configured on interface bri0: 

Router# show running-config

.

.

.

interface multilink1

 ip address 10.0.0.0 255.255.255.0

   encapsulation ppp

   ppp authentication chap

   ppp multilink

   ppp multilink max-links 100

   ppp multilink min-links 10 mandatory

  

  interface BRI2/1

   no ip address

   encapsulation ppp

   dialer pool-member 2

   no fair-queue

   no cdp enable

   ppp authentication chap

   ppp multilink

 

 interface bri 0

  description connected to abc 81012345678902

  ip address 172.16.0.10 255.255.255.0

  encapsulation ppp

  dialer idle-timeout 30

  dialer map ip 172.16.0.0 name cisco 81012345678901

  dialer-group 1

  ppp authentication pap

  ppp multilink

  ppp multilink min-links 2 mandatory ! Indicates that the Multilink PPP Minimum Links 
                                        Mandatory feature is enabled.

Configuration Examples for Multilink PPP Minimum Links Mandatory

This section provides the following configuration examples:

•Configuring PPP: Example

•Configuring Multilink PPP: Example

•Configuring Multilink PPP Minimum Links Mandatory: Example

Configuring PPP: Example

The following example shows how to configure PPP on a serial interface with CHAP authentication: 

interface serial 1/0

 encapsulation ppp

 ppp authentication chap

 exit

username abc password password1

Configuring Multilink PPP: Example

The following example shows how to configure MLP. In this example, the MLP bundle is configured with CHAP authentication. The minimum number of links for this MLP bundle is 5 and the maximum number of links is 100. 

interface multilink 3

 ip address 172.16.0.0

 encapsulation ppp

 ppp multilink

 ppp multilink max-links 100

 ppp multilink min-links 5

 bridge-group 2

 no shutdown

Configuring Multilink PPP Minimum Links Mandatory: Example

The following example shows how to configure an MLP bundle to be required to have at least five active sessions: 

ppp multilink

ppp multilink min-links 5 mandatory

Additional References

The following sections provide references related to the Multilink PPP Minimum Links Mandatory feature.

Related Documents

Related Topic
Document Title

Dial technologies commands

Cisco IOS Dial Technologies Command Reference

PPP and multilink PPP configuration

•Configuring Media-Independent PPP and Multilink PPP

•Configuring PPP

•Multichassis Multilink PPP (MMP)

•Router-to-Router Async Multilink PPP

•Troubleshooting Async Multilink PPP Operations 


Standards

Standards
Title

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

—


MIBs

MIBs
MIBs Link

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

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

RFCs
Title

RFC 1990

The PPP Multilink Protocol (MP)


Technical Assistance

Description
Link

The Cisco Technical Support & Documentation website contains thousands of 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

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Dial Technologies Command Reference at http://www.cisco.com/en/US/docs/ios/dia/command/reference/dia_book.html For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

•multilink min-links

•ppp multilink links minimum


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