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This module contains conceptual information and configuration tasks for using Multilink PPP over serial interface links. Multilink PPP is a method used to reduce latency and jitter for real-time traffic.
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 Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
If a multilink bundle has one link or packet order is not important for interleaved packets, use Link Fragmentation and Interleaving (LFI) without multiclass. Use LFI with multiclass if a multilink bundle has multiple links.
Only Voice over IP (VoIP) is supported.
Many of the legacy queueing mechanisms are not supported by multilink. These mechanisms include:
Note |
Fair queueing, WRED, and priority queueing can be configured in a traffic policy using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC). |
Before using Multilink PPP over serial interface links, a traffic policy (also known as a policy map) must be created. (See the "Prerequisites" section on page 3 .) Policy maps are created using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC).
The MQC is a CLI structure that allows users to create traffic polices (policy maps) and attach these policy maps to interfaces. A policy map contains a traffic class and one or more QoS features. A traffic class is used to classify traffic. The QoS features in the traffic policy determine how to treat the classified traffic.
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.
Before proceeding with this task, you must create a policy map. The policy map contains the configuration parameters used to apply the specific quality of service feature to the network traffic. To create a policy map, use the MQC. See the MQC and Multilink PPP over Serial Interface Links.
Command or Action | Purpose | |||
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Example: Router> enable |
Enables privileged EXEC mode.
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Example: Router# configure terminal |
Enters global configuration mode. |
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Example: Router(config)# interface multilink 1 |
Creates a multilink bundle and enters interface configuration mode.
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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.
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Example: Router(config-if)# service-policy output policy1 |
Attaches the previously created QoS traffic policy (policy map). See the "Prerequisites" section on page 3 . The policy map evaluates and applies QoS features for traffic leaving the interface.
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Example: Router(config-if)# service-policy input policy1 |
Attaches the previously created QoS traffic policy (policy map). See the "Prerequisites" section on page 3 . The policy map evaluates and applies QoS features for traffic enteringthe interface.
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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.
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Example: Router(config-if)# ppp multilink interleave |
Enables interleaving of packets among the fragments of larger packets on a multilink bundle. |
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Example: Router(config-if)# ppp multilink multiclass |
(Optional) Enables Multiclass Multilink PPP (MCMP) on an interface.
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Example: Router(config-if)# end |
(Optional) Exits interface configuration mode. |
The following is an example of configuring Multilink PPP over serial interface links 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)# ppp multilink multiclass
Router(config-if)# end
The following is an example of associating the serial interface serial4/1 with the multilink group:
Router> enable
Router# configure terminal
Router(config)# interface serial 4/1:23
Router(config-if)# no fair-queue
Router(config-if)# encapsulation ppp
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink group 1
Router(config-if)# end
You can verify the Multilink PPP over serial interface links configuration by using one or more of the following show commands:
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.
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
Multilink2, bundle name is 7206-2
Endpoint discriminator is 7206-2
Bundle up for 00:00:09, 1/255 load
Receive buffer limit 12000 bytes, frag timeout 1500 ms
0/0 fragments/bytes in reassembly list
0 lost fragments, 0 reordered
0/0 discarded fragments/bytes, 0 lost received
0x0 received sequence, 0x3 sent sequence
Member links:1 active, 1 inactive (max not set, min not set)
Se3/2, since 00:00:10, 240 weight, 232 frag size
Se3/3 (inactive)
To use Multilink PPP over ATM links, see the "Using Multilink PPP over ATM Links" module.
To use Multilink PPP over Frame Relay, see the "Using Multilink PPP over Frame Relay" module.
To use Multilink PPP over dialer interface links, see the "Using Multilink PPP over Dialer Interface Links" module.
The following sections provide references related to Multilink PPP over serial interface links:
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 |
Multilink PPP configurations |
"Configuring Media-Independent PPP and Multilink PPP" 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 Frame Relay |
"Using Multilink PPP over Frame Relay" module |
Multilink PPP over dialer interface links |
"Using Multilink PPP over Dialer Interface Links" module |
Standard |
Title |
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No new or modified standards are supported, and support for existing standards has not been modified. |
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MIB |
MIBs Link |
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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: |
RFC |
Title |
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RFC 1990 |
The PPP Multilink Protocol (MP) |
RFC 2686 |
Multiclass Extension to Multilink PPP (MCML) |
Description |
Link |
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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. |
The following table provides release information about the feature or features described in this module. This table 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.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1 | Feature Information for Using Multilink PPP over Serial Interface Links |
Feature Name |
Software Releases |
Feature Configuration Information |
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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 serial interface links. |
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 serial interface links. |
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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.