Using Multilink PPP over Frame Relay

Multilink PPP is a method used to reduce latency and jitter for real-time traffic. This module contains conceptual information and configuration tasks for using Multilink PPP over Frame Relay.

Module History

This module was first published on May 2, 2005, and last updated on May 2, 2005.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for Using Multilink PPP over Frame Relay" section.

Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images

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

•Prerequisites for Using Multilink PPP over Frame Relay

•Restrictions for Using Multilink PPP over Frame Relay

•Information About Using Multilink PPP over Frame Relay

•How to Configure Multilink PPP over Frame Relay

•Configuration Examples for Multilink PPP over Frame Relay

•Where to Go Next

•Additional References

•Feature Information for Using Multilink PPP over Frame Relay

Prerequisites for Using Multilink PPP over Frame Relay

Knowledge

•Be familiar with the concepts in the "Reducing Latency and Jitter for Real-Time Traffic Using Multilink PPP" module.

Enable Queuing Mechanism

•Multilink uses first-in first out (FIFO) queuing for queuing and interleaving packets. Other queuing mechanisms such as low latency queuing (LLQ), weighted fair queuing (WFQ), and class-based weighted fair queuing (CBWFQ) can be used. If you want to use one of these alternative mechanisms, enable it before configuring Multilink.

Enable FRTS

•Frame Relay Traffic Shaping (FRTS) must be enabled on the Frame Relay interface.

Restrictions for Using Multilink PPP over Frame Relay

Number of Links per Multilink Bundle

Only one link per multilink bundle is supported.

VoIP Support

Only Voice over IP (VoIP) is supported; Voice over Frame Relay (VoFR) is not supported.

Information About Using Multilink PPP over Frame Relay

To use Multilink PPP over Frame Relay, you should understand the following concepts:

•Frame Relay Traffic Shaping and Multilink PPP over Frame Relay

•MQC and Multilink PPP over Frame Relay

•Multilink Group Interfaces

Frame Relay Traffic Shaping and Multilink PPP over Frame Relay

Before using Multilink PPP over Frame Relay, FRTS must be enabled.

Note On the Cisco 7200 and lower series of routers, the frame-relay traffic-shaping command is used to enable FRTS. On the Cisco 7500 and higher series of routers, the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC) is used to enable FRTS. For more information about MQC, see the "MQC and Multilink PPP over Frame Relay" section.

FRTS is a Cisco traffic shaping mechanism. A traffic shaping mechanism allows you to regulate (that is, "shape") the packet flow on a network. When you shape traffic, you control the speed of traffic leaving an interface. This way, you can match the flow of the traffic to the speed of the interface and avoid bottlenecks on the network.

Cisco has long provided support for forward explicit congestion notification (FECN) for DECnet and OSI, and backward explicit congestion notification (BECN) for Systems Network Architecture (SNA) traffic using Logical Link Control, type 2 (LLC2) encapsulation via RFC 1490 and discard eligible (DE) bit support. FRTS builds upon this existing Frame Relay support with additional capabilities that improve the scalability and performance of a Frame Relay network, increasing the density of virtual circuits (VCs) and improving response time.

FRTS can eliminate bottlenecks in Frame Relay networks that have high-speed connections at the central site and low-speed connections at branch sites. You can configure rate enforcement—a peak rate configured to limit outbound traffic—to limit the rate at which data is sent on the VC at the central site.

MQC and Multilink PPP over Frame Relay

Before using Multilink PPP over Frame Relay, a policy map must be created. (See the "Prerequisites" section.) Policy maps are created using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC).

Virtual Template Interfaces

A virtual template interface is logical interface configured with generic configuration information for a specific purpose or configuration common to specific users, plus router-dependent information. The template takes the form of a list of Cisco IOS interface commands that are applied to virtual access interfaces, as needed.

Multilink Group Interfaces

A multilink group interface is a collection of interfaces bundled together in the multilink PPP configuration. With a multilink group interface, you can bundle interfaces into logical multilink groups.

How to Configure Multilink PPP over Frame Relay

This section contains the procedures for configuring Multilink PPP over Frame Relay.

Note While the first two procedures are listed as optional, you must choose one or the other according to the Cisco router you are using on your network.

•Configuring Multilink PPP over Frame Relay on a Virtual Template Interface (optional; applies only if you are using the Cisco 7500 series router or the Cisco 7600 series router)

or

•Configuring Multilink PPP over Frame Relay on a Multilink Group Interface (optional)

•Associating the Virtual Template Interface with a Frame Relay PVC (required)

•Verifying the Multilink PPP over Frame Relay Configuration (optional)

Configuring Multilink PPP over Frame Relay on a Virtual Template Interface

Note These steps apply if you are using the Cisco 7500 series router or the Cisco 7600 series router only. If you are using another series of Cisco router, do not complete these steps. Instead, advance to "Configuring Multilink PPP over Frame Relay on a Multilink Group Interface" section.

Prerequisites

Before proceeding with this task, you must create a policy map. The policy map contains the configuration parameters used to apply a specific QoS features such as distributed LLQ (dLLQ) to the network traffic. To create a policy map and configure the appropriate QoS feature, use the MQC. See the "MQC and Multilink PPP over Frame Relay" section.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface virtual-template number

4. bandwidth kbps

5. ip address ip-address mask [secondary]

6. service-policy output policy-map-name

7. service-policy input policy-map-name

8. ppp multilink

9. ppp multilink fragment delay milliseconds [microseconds]

10. ppp multilink interleave

11. 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 virtual-template number

Example:

Router(config)# interface virtual-template 1

Creates a virtual template and enters interface configuration mode.

•Enter the virtual template number.

Step 4 

bandwidth kbps

Example:

Router(config-if)# bandwidth 32

Sets the bandwidth value for an interface.

•Enter the bandwidth value in kilobits per second.

Note The bandwidth value for the interface should match the traffic speed of the PVC; for instance, if the VBR peak cell rate is 128 kbps, the kbps option in the bandwidth command should be entered as 128. Similarly, if the PVC is being shaped to 64 kbps, the kbps option should be entered as 64.

Step 5  

ip address ip-address mask [secondary]
Example: 
Router(config-if)# ip address 10.10.100.1 
255.255.255.0

Sets a primary IP address for an interface. This command can also set the optional secondary IP address for an interface.

•Enter the primary IP address (and, optionally, the secondary IP address).

Step 6  

service-policy output policy-map-name
Example:

Router(config-if)# service-policy output policy1

Attaches the previously created QoS traffic policy (policy map). See the "Prerequisites" section. The policy map evaluates and applies QoS features for traffic leaving the interface.

•Enter the policy map name.

Step 7  

service-policy input policy-map-name
Example:

Router(config-if)# service-policy input policy1

Attaches the previously created QoS traffic policy (policy map). See the "Prerequisites" section. The policy map evaluates and applies QoS features for traffic entering the interface.

•Enter the policy map name.

Step 8 

ppp multilink

Example:

Router(config-if)# ppp multilink

Enables MLP on the interface.

Step 9 

ppp multilink fragment delay milliseconds [microseconds]

Example:

Router(config-if)# ppp multilink fragment delay 20

Specifies a maximum size in units of time for packet fragments on a Multilink PPP (MLP) bundle.

•Enter the maximum amount of time, in milliseconds.

Note The fragment size can be configured using the following formula:

fragment size = bandwidth x fragment-delay / 8

Step 10 

ppp multilink interleave

Example:

Router(config-if)# ppp multilink interleave

Enables interleaving of packets among the fragments of larger packets on a multilink bundle.

Step 11 

end

Example:

Router(config-if)# end

(Optional) Exits interface configuration mode.

Configuring Multilink PPP over Frame Relay on a Multilink Group Interface

Note If you are using the Cisco 7500 series router or the Cisco 7600 series router, do not complete these steps. Instead, complete the steps in "Configuring Multilink PPP over Frame Relay on a Virtual Template Interface" section.

Prerequisites

Before proceeding with this task, you must create a policy map. The policy map contains the configuration parameters used to apply a specific QoS features such as distributed LLQ (dLLQ) to the network traffic. To create a policy map and configure the appropriate QoS feature, use the MQC. See the "MQC and Multilink PPP over Frame Relay" section.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface multilink multilink-bundle-number

4. ip address ip-address mask [secondary]

5. service-policy output policy-map-name

6. service-policy input policy-map-name

7. ppp multilink fragment delay milliseconds [microseconds]

8. ppp multilink interleave

9. 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 multilink multilink-bundle-number

Example:

Router(config)# interface multilink 1

Creates a multilink bundle and enters interface configuration mode.

•Enter the multilink bundle number.

Step 4  

ip address ip-address mask [secondary]
Example: 
Router(config-if)# ip address 10.10.100.1 
255.255.255.0

Sets a primary IP address for an interface. This command can also set the optional secondary IP address for an interface.

•Enter the primary IP address (and, optionally, the secondary IP address).

Step 5  

service-policy output policy-map-name
Example:

Router(config-if)# service-policy output policy1

Attaches the previously created QoS traffic policy (policy map). See the "Prerequisites" section. The policy map evaluates and applies QoS features for traffic leaving the interface.

•Enter the policy map name.

Step 6  

service-policy input policy-map-name
Example:

Router(config-if)# service-policy input policy1

Attaches the previously created QoS traffic policy (policy map). See the "Prerequisites" section. The policy map evaluates and applies QoS features for traffic entering the interface.

•Enter the policy map name.

Step 7 

ppp multilink fragment delay milliseconds [microseconds]

Example:

Router(config-if)# ppp multilink fragment delay 20

Specifies a maximum size in units of time for packet fragments on a multilink bundle.

•Enter the maximum amount of time, in milliseconds, required to transmit a fragment.

Step 8 

ppp multilink interleave

Example:

Router(config-if)# ppp multilink interleave

Enables interleaving of packets among the fragments of larger packets on a multilink bundle.

Step 9 

end

Example:

Router(config-if)# end

(Optional) Exits interface configuration mode.

What to Do Next

After configuring Multilink PPP over Frame Relay on a multilink group interface, the next step is to associate the virtual template interface with the multilink group by completing the steps in the following section.

If you are using a Cisco 7500 series router or a Cisco 7600 series router, advance to "Associating the Virtual Template Interface with a Frame Relay PVC" section to continue.

Associating the Virtual Template Interface with the Multilink Group

SUMMARY STEPS

1. enable

2. configure terminal

3. interface virtual-template number

4. no ip address

5. ppp multilink group group-number

6. 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 virtual-template number

Example:

Router# interface virtual-template 1

Creates a virtual template interface that can be configured and applied dynamically in creating virtual access interfaces, and enters interface configuration mode.

•Enter the number used to identify the virtual template interface.

Step 4 

no ip address

Example:

Router(config-if)# no ip address

Removes an IP address or disables IP processing.

Step 5 

ppp multilink group group-number

Example:

Router(config-if)# ppp multilink group 1

Restricts a physical link to joining only a designated multilink group interface.

•Enter the multilink group number.

Step 6 

end

Example:

Router(config-if)# end

(Optional) Exits interface configuration mode.

Associating the Virtual Template Interface with a Frame Relay PVC

SUMMARY STEPS

1. enable

2. configure terminal

3. interface type number [name-tag]

4. frame-relay traffic-shaping

5. frame-relay interface-dlci dlci [ietf | cisco] [voice-cir cir] [ppp virtual-template-name]

6. class name

7. 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 [name-tag]

Example:

Router(config)# interface serial1/0/0/1:0

Configures an interface type and enters interface configuration mode.

•Enter the interface type and number.

Step 4 

frame-relay traffic-shaping

Example:

Router(config-if)# frame-relay traffic-shaping

Enables both traffic shaping and per-virtual-circuit queueing for all permanent virtual circuits (PVCs) and switched virtual circuits (SVCs) on a Frame Relay interface.

Note Use this command on Cisco 7200 and lower series routers only. Do not use this command on Cisco 7500 or higher series routers. For Cisco 7500 and higher series routers, use the MQC instead of this command.

Step 5 

frame-relay interface-dlci dlci [ietf | cisco] [voice-cir cir] [ppp virtual-template-name]

Example:

Router(config-if)# frame-relay interface-dlci 100 ppp virtual-template1

Assigns a data-link connection identifier (DLCI) to a specified Frame Relay subinterface on the router or access server, assigns a specific PVC to a DLCI, or applies a virtual template configuration for a PPP session. Enters Frame Relay DLCI configuration mode.

•Enter the DLCI number and any optional keywords and arguments, as appropriate.

Step 6 

class name

Example:

Router(config-fr-dlci)# class frdlci

Associates a map class with a specified DLCI.

•Enter the name of the map class to associate with the specified DLCI.

Note Use this command on Cisco 7200 and lower series routers only. For Cisco 7500 and higher series routers, this command is not needed.

Step 7 

end

Example:

Router(config-fr-dlci)# end

(Optional) Exits Frame Relay DLCI configuration mode.

Verifying the Multilink PPP over Frame Relay Configuration

SUMMARY STEPS

1. enable

2. show frame-relay pvc [interface interface] [dlci] [64-bit]

3. show interfaces [type number] [first] [last] [accounting]

4. show ppp multilink [active | inactive | interface bundle-interface | [username name] [endpoint endpoint]]

5. show policy-map interface interface-name [vc [vpi/] vci] [dlci dlci] [input | output]

6. 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 frame-relay pvc [interface interface] 
[dlci] [64-bit]
Example:

Router# show frame-relay pvc

(Optional) Displays statistics about permanent virtual circuits (PVCs) for Frame Relay interfaces.

Step 3  

show interfaces [type number] [first] [last] 
[accounting]
Example:

Router# show interfaces

(Optional) Displays statistics for all interfaces configured on the router or access server.

Step 4  

show ppp multilink [active | inactive | 
interface bundle-interface | [username name] 
[endpoint endpoint]]
Example:

Router# show ppp multilink

(Optional) Displays bundle information for multilink bundles.

Step 5  

show policy-map interface interface-name [vc 
[vpi/] vci] [dlci dlci] [input | output]
Example:

Router# show policy-map interface serial0/0

(Optional) Displays the packet statistics of all classes that are configured for all service policies either on the specified interface or subinterface or on a specific PVC on the interface.

Step 6 

exit

Example:

Router# exit

(Optional) Exits privileged EXEC mode.

Configuration Examples for Multilink PPP over Frame Relay

This section contains the following examples:

•Example: Configuring Multilink PPP over Frame Relay on a Virtual Template Interface

•Example: Configuring Multilink PPP over Frame Relay on a Multilink Group Interface

•Example: Associating the Virtual Template Interface with the Multilink Group

•Example: Associating the Virtual Template Interface with a Frame Relay PVC

•Example: Verifying the Multilink PPP over Frame Relay Configuration

Example: Configuring Multilink PPP over Frame Relay on a Virtual Template Interface

The following is an example of configuring Multilink PPP over Frame Relay on a virtual template interface:

Router> enable

Router# configure terminal

Router(config)# interface virtual-template 1

Router(config-if)# bandwidth 32 

Router(config-if)# ip address 10.10.100.1 255.255.255.0

Router(config-if)# service-policy output policy1

Router(config-if)# service-policy input policy1

Router(config-if)# ppp multilink

Router(config-if)# ppp multilink fragment delay 20

Router(config-if)# ppp multilink interleave

Router(config-if)# end

Example: Configuring Multilink PPP over Frame Relay on a Multilink Group Interface

The following is an example of configuring Multilink PPP over Frame Relay on a multilink group interface:

Router> enable

Router# configure terminal

Router(config)# interface multilink 1 

Router(config-if)# ip address 10.10.100.1 255.255.255.0

Router(config-if)# service-policy output policy1

Router(config-if)# service-policy input policy1

Router(config-if)# ppp multilink fragment delay 20

Router(config-if)# ppp multilink interleave

Router(config-if)# end

Example: Associating the Virtual Template Interface with the Multilink Group

The following is an example of associating the virtual template interface with the multilink group:

Router> enable

Router# configure terminal

Router(config)# interface virtual-template 1

Router(config-if)# no ip address

Router(config-if)# ppp multilink group 1

Router(config-if)# end


Example: Associating the Virtual Template Interface with a Frame Relay PVC

The following is an example of associating the virtual template interface with a Frame Relay PVC:

Router> enable

Router# configure terminal

Router(config)# interface serial1/0/0/1:0

Router(config-if)# frame-relay interface-dlci 100 ppp virtual-template1

Router(config-fr-dlci)# class frdlci

Router(config-fr-dlci)# end

Example: Verifying the Multilink PPP over Frame Relay Configuration

You can verify the Multilink with PPP over Frame Relay configuration by using one or more of the following show commands:

•show frame relay pvc

•show interfaces

•show ppp multilink

•show policy-map interface

The following section provides sample output of the show ppp multilink command only. For sample output of the other commands, see the appropriate Cisco IOS Release 12.3 T command reference publication.

show ppp multilink Command Output Example

The following is an example of the show ppp multilink command output. In this example, one Multilink bundle called 7206-2 is on the system. This bundle has two member links: one active link and one inactive link. 

Router# show ppp multilink


Multilink1, bundle name is 7206-2

  Endpoint discriminator is 7206-2

  Bundle up for 00:00:15, 1/255 load

  Receive buffer limit 12000 bytes, frag timeout 3428 ms

    0/0 fragments/bytes in reassembly list

    1 lost fragments, 1 reordered

    0/0 discarded fragments/bytes, 0 lost received

    0x3 received sequence, 0x3 sent sequence

  Member links:1 active, 1 inactive (max not set, min not set)

    Vi2, since 00:00:15, 105 weight, 93 frag size

    Vt1 (inactive)

Where to Go Next

To use Multilink PPP over ATM links, see the "Using Multilink PPP over ATM Links" module.

To use Multilink PPP over dialer interface links, see the "Using Multilink PPP over Dialer Interface Links" module.

To use Multilink PPP over serial interface links, see the "Using Multilink PPP over Serial Interface Links" module.

Additional References

The following sections provide references related to using Multilink PPP over Frame Relay.

Related Documents

Related Topic
Document Title

QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco IOS Quality of Service Solutions Command Reference

LLQ, WFQ, CBWFQ, PQ, CQ, FIFO and other queueing mechanisms

"Configuring Weighted Fair Queueing" module

MQC

"Applying QoS Features Using the MQC" module

FRTS

"MQC-Based Frame Relay Traffic Shaping" module

Multilink PPP configurations

"Configuring Media-Independent PPP and Multilink PPP" module

Virtual template interfaces

"Configuring Virtual Template Interfaces" module

Multilink PPP overview module

"Reducing Latency and Jitter for Real-Time Traffic Using Multilink PPP" module

Multilink PPP over ATM links (including ATM interfaces and ATM PVCs)

"Using Multilink PPP over ATM Links" module

Multilink PPP over dialer interface links

"Using Multilink PPP over Dialer Interface Links" module

Multilink PPP over serial interface links

"Using Multilink PPP over Serial Interface Links" module


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.

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

RFC 1990

The PPP Multilink Protocol (MP)

RFC 2686

Multiclass Extension to Multilink PPP (MCML)


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 Using Multilink PPP over Frame Relay

Table 1 lists the features in this module.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS 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 Using Multilink PPP over Frame Relay

Feature Name
Software Releases
Feature Configuration Information

Distributed Link Fragmentation and Interleaving Over Leased Lines

12.2(8)T

The Distributed Link Fragmentation and Interleaving over Leased Lines feature extends distributed link fragmentation and interleaving functionality to leased lines.

This feature was extensively rewritten from the perspective of using Multilink PPP for link fragmentation and interleaving over Frame Relay.

The following sections provide information about this feature:

•Information About Using Multilink PPP over Frame Relay

•How to Configure Multilink PPP over Frame Relay

Distributed Link Fragmentation and Interleaving for Frame Relay and ATM Interfaces on Cisco 7500 Series Routers

12.2(4)T

The Distributed Link Fragmentation and Interleaving (dLFI) for Frame Relay and ATM Interfaces on Cisco 7500 Series Routers feature extends link fragmentation and interleaving functionality to VIP-enabled Cisco 7500 series routers.

This feature was extensively rewritten from the perspective of using Multilink PPP for link fragmentation and interleaving over Frame Relay.

The following sections provide information about this feature:

•Information About Using Multilink PPP over Frame Relay

•How to Configure Multilink PPP over Frame Relay


Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

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.

© 2011 Cisco Systems, Inc. All rights reserved.