Table Of Contents
Prerequisites for Multiclass Multilink PPP
Restrictions for Multiclass Multilink PPP
Information About the Multiclass Multilink PPP Feature
How to Configure Multiclass Multilink PPP
Multiclass Multilink PPP Configuration Guidelines
Configuring Multiclass Multilink PPP LFI on a Bundle
Configuring Multiclass Multilink PPP on a Member Link
Verifying Multiclass Multilink PPP
Configuration Examples for Multiclass Multilink PPP
Configuring Multiclass Multilink Classes on Bundles: Example
Configuring Multiclass Multilink Peer Options: Examples
Configuring the Fragment Timeout: Example
Disabling MultiClass Multilink PPP: Example
ppp timeout multilink lost-fragment
Feature Information for Multiclass Multilink PPP
Multiclass Multilink PPP
First Published: November, 2006
This document describes the multiclass multilink PPP feature on the Cisco 10000 series router. This feature provides the ability to fragment packets of various priorities into multiple classes, allowing high-priority packets to be sent between fragments of lower priorities.
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. 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 Multiclass Multilink PPP" section.
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
•Prerequisites for Multiclass Multilink PPP
•Restrictions for Multiclass Multilink PPP
•Information About the Multiclass Multilink PPP Feature
•How to Configure Multiclass Multilink PPP
•Configuration Examples for Multiclass Multilink PPP
•Feature Information for Multiclass Multilink PPP
Prerequisites for Multiclass Multilink PPP
•The multilink interface must be configured with PPP encapsulation enabled.
•Link Fragmentation and Interleaving (LFI) must be configured on the bundle. Refer to the "Configuring Multiclass Multilink PPP LFI on a Bundle" section.
Restrictions for Multiclass Multilink PPP
•This feature is only supported on serial interfaces with PPP encapsulation in a multilink PPP (MLPPP) bundle.
•Multiclass multilink PPP is not supported on ATM virtual circuits (VCs) in a Multilink PPP over ATM (MLPoA) bundle, Link Fragmentation and Interleaving over ATM (LFIoA) bundle, or Multilink PPP over Frame Relay (MLPoFR) encapsulated serial interfaces.
•The Prefix Elision and Short Sequence Numbers options in RFC 2686 are not supported.
Information About the Multiclass Multilink PPP Feature
Multiclass multilink PPP provides the ability to fragment packets of various priorities into multiple classes, allowing high-priority packets to be sent between fragments of lower priorities. In multiclass multilink PPP, outgoing packets can be divided into four different multilink classes. Each class has its own governing sequence number, and the receiving network peer (bundle) sorts and processes each class independently. Sequence numbers are embedded in the multilink header and used internally to reassemble packets.
Multiclass multilink PPP must be successfully negotiated with the peer system. If multiclass multilink PPP cannot be negotiated with the peer system, the router uses standard interleaving, Priority queue traffic is always PPP encapsulated when interleaving with non-priority traffic.
Scalability
The Cisco 10000 series router supports a maximum of 1996 multilink classes and 1250 multilink bundles, with up to four classes in each bundle. Table 1 lists the number of bundles that are supported system-wide based on the number of multilink classes in a bundle.
Table 1 Maximum Multiclass Multilink PPP Bundles
Number of Multiclass Multilink PPP Classes Per Bundle Maximum Number of Multiclass Multilink PPP Bundles1
1250
2
998
3
665
4
499
How to Configure Multiclass Multilink PPP
This section includes the following multiclass multilink PPP procedures:
•Multiclass Multilink PPP Configuration Guidelines
•Configuring Multiclass Multilink PPP LFI on a Bundle
•Configuring Multiclass Multilink PPP on a Member Link
•Verifying Multiclass Multilink PPP
Multiclass Multilink PPP Configuration Guidelines
•The ppp multilink multiclass command must be configured on each link that is a member of the bundle, or on the multilink interface itself when multilink groups are used. Failure to configure this command may result in the peer refusing to allow mismatched links to join the bundle. The first link to join the bundle determines whether multiclass multilink PPP is in effect for the bundle. Each subsequent link must negotiate the same multiclass multilink PPP parameters to join the bundle.
•A maximum of four multilink classes is allowed in each multiclass multilink PPP bundle.
•The number of transmit classes negotiated with the peer must be greater than the highest encapsulation sequence class number configured in the outbound service policy. The service policy is rejected if the number of transmit classes is too small.
•The fragment size is computed at the interface multilink level when the first link is added to the bundle, and it applies to all links and classes.
•The configuration for each link in a bundle must be identical.
•A bundle configuration must be applied prior to the start of the PPP Link Control Protocol (LCP). You can apply this configuration on a multilink interface and then add all links to a multilink group.
•The default sequence number for class-default is 0 and it is not configurable.
Configuring Multiclass Multilink PPP LFI on a Bundle
Use the following procedure to configure multiclass multilink PPP LFI on a bundle.
SUMMARY STEPS
1. enable
2. configure terminal
3. interface multilink multilink-bundle-number
4. ip address ip_address mask
5. ppp multilink
6. ppp multilink interleave
7. ppp multilink fragment delay milliseconds [microseconds]
8. ppp timeout multilink lost-fragment seconds [milliseconds]
9. ppp multilink multiclass local {request [initial init-value] [maximum max-value] | allow [maximum max-value] | forbid}
10. ppp multilink multiclass remote {apply [minimum min-value] | reject | ignore}
11. no cdp enable
12. exit
DETAILED STEPS
Examples
Router> enable
Router# configure terminal
Router(config)# interface multilink 1
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 0 500
Router(config-if)# ppp timeout multilink lost-fragment 0 100
Router(config-if)# ppp multilink multiclass local request maximum 4
Router(config-if)# ppp multilink multiclass remote apply minimum 4
Router(config-if)# no cdp enable
Router(config-if)# exit
Configuring Multiclass Multilink PPP on a Member Link
Use the following procedure to configure multiclass multilink PPP on a configured and operational member link.
SUMMARY STEPS
1. enable
2. configure terminal
3. interface interface
4. ppp multilink
5. ppp multilink multiclass
6. no cdp enable
7. exit
DETAILED STEPS
Examples
Router> enable
Router# configure terminal
Router(config)# interface serial0/0/0
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink multiclass
Router(config-if)# no cdp enable
Router(config-if)# exit
Verifying Multiclass Multilink PPP
To verify that the multiclass multilink PPP feature is configured correctly, enter the show ppp multilink command in privileged EXEC mode. The following output includes class-specific information for the PPP Multilink bundles:
Router# show ppp multilink
Multilink1, bundle name is corkBundle up for 01:59:35, 1/255 load, 2 receive classes, 2 transmit classes!Receive Class 0:51 lost fragments, 432 reordered, 0 unassigned0 discarded, 0 lost received0xC36E received sequence!Receive Class 1:0 lost fragments, 0 reordered, 0 unassigned0 discarded, 0 lost received0x0 received sequence!Transmit Class 0:0xC170 sent sequence!Transmit Class 1:0x0 sent sequence!Member links: 2 active, 0 inactive (max not set, min not set)Serial0, since 01:59:35 160 weight, 154 bytesSerial1, since 01:59:35 160 weight, 32 bytesConfiguration Examples for Multiclass Multilink PPP
This section provides the following configuration examples:
•Configuring Multiclass Multilink Classes on Bundles: Example
•Configuring Multiclass Multilink Peer Options: Examples
•Configuring the Fragment Timeout: Example
•Disabling MultiClass Multilink PPP: Example
Configuring Multiclass Multilink Classes on Bundles: Example
The following example shows how to configure a multilink bundle for up to four receive classes and at least four transmit classes:
Router(config)# interface multilink 9
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 20
Router(config-if)# ppp multilink multiclass local request maximum 4
Router(config-if)# ppp multilink multiclass remote apply minimum 4
Router(config-if)# no cdp enable
Configuring Multiclass Multilink Peer Options: Examples
The following example shows how to configure a multilink bundle to not use multiple classes but allows the peer to request the option and transmit up to four classes when needed:
Router(config)# interface multilink 9
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 20
Router(config-if)# ppp multilink multiclass local allow maximum 4
Router(config-if)# ppp multilink multiclass remote ignore
Router(config-if)# no cdp enable
The following example shows how to configure a multilink bundle to not use multiple classes, but allows the peer to request the option and inform the peer that the option is supported, allowing for up to four receive classes:
Router(config)# interface multilink 9
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 20
Router(config-if)# ppp multilink multiclass local request initial 1 maximum 4
Router(config-if)# ppp multilink multiclass remote ignore
Router(config-if)# no cdp enable
Configuring the Fragment Timeout: Example
The following example sets a 5-second wait period for receiving expected fragments before declaring the fragments lost:
Router(config)# interface multilink 9
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 20
Router(config-if)# ppp timeout multilink lost-fragment 5
The following example sets a 100-millisecond wait period for receiving expected fragments before declaring the fragments lost:
Router(config)# interface multilink 9
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 20
Router(config-if)# ppp timeout multilink lost-fragment 0 100
Disabling MultiClass Multilink PPP: Example
The following example shows how to completely disable multiclass multilink PPP, rejecting the option and declining to allow the peer to transmit multiple classes:
Router(config)# interface multilink 9
Router(config-if)# ip address 10.0.0.161 255.255.255.240
Router(config-if)# ppp multilink
Router(config-if)# ppp multilink interleave
Router(config-if)# ppp multilink fragment delay 20
Router(config-if)# ppp multilink multiclass local forbid
Router(config-if)# ppp multilink multiclass remote reject
Router(config-if)# no cdp enable
Additional References
The following sections provide references related to the multiclass multilink PPP feature.
Related Documents
Related Topic Document TitleProvisioning Qos
Cisco 10000 Series Router Quality of Service Configuration Guide
Configuring Multilink PPP Connections
Cisco 10000 Series Router Broadband Aggregation, Leased-Line, and MPLS Configuration Guide
Configuring Cisco 10000 series router line cards
Standards
Standard TitleNo new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
—
MIBs
RFCs
Technical Assistance
Command Reference
This section documents new commands only.
New Commands
•ppp timeout multilink lost-fragment
encap-sequence
To assign an encapsulation sequence number to a priority class in a multiclass multilink PPP bundle, use the encap-sequence command in policy-map class configuration mode. To reset the default value, use the no form of this command.
encap-sequence [sequence-id | none]
no encap-sequence sequence-id
Syntax Description
Command Default
Sequence numbers are not assigned to priority classes.
Command Modes
Policy-map class configuration
Command History
Release Modification12.2(31)SB2
This command was introduced and implemented on the Cisco 10000 series router for the PRE2.
Usage Guidelines
The encap-sequence command allows you to assign sequence numbers to priority classes in a policy map for multiclass multilink PPP encapsulation. This command is only supported on the PRE2.
A class with a multiclass multilink PPP sequence number must have an associated queue action such as bandwidth and shape. The sequence number assigned to each priority class must be unique.
The default sequence number for class-default is 0 and it is not configurable.
If you do not assign a sequence number to a priority class, the priority queue packets use PPP encapsulation. Interleaving is allowed for priority traffic regardless of the encapsulated sequence number configuration.
Examples
The following example shows that class voice has the highest priority and that packets are not encapsulated with a sequence number for multiclass multilink PPP.
Router(config)# policy-map prec1
Router(config-pmap)# class voice
Router(config-pmap-c)# priority
Router(config-pmap-c)# police 128
Router(config-pmap-c)# encap-sequence none
Router(config-pmap-c)# exit
Router(config-pmap)# class video
Router(config-pmap-c)# bandwidth 1000
Router(config-pmap-c)# police 1000
Router(config-pmap-c)# encap-sequence 1
Router(config-pmap-c)# exit
Router(config-pmap)# class game
Router(config-pmap-c)# bandwidth 1000
Router(config-pmap-c)# encap-sequence 2
Router(config-pmap-c)# exit
Router(config-pmap)# class class-default
Related Commands
ppp multilink multiclass
To enable multiclass multilink PPP on an interface, use the ppp multilink multiclass command in interface configuration mode. To disable multiclass multilink PPP, use the no form of this command.
ppp multilink multiclass [local {request [initial init-value] [maximum max-value] | allow [maximum max-value] | forbid} | [remote {apply [minimum min-value] | reject | ignore}]
no ppp multilink multiclass [local {request [initial init-value] [maximum max-value] | allow [maximum max-value] | forbid} | [remote {apply [minimum min-value] | reject | ignore}]
Syntax Description
Command Default
Initially omits the multilink header format option when negotiating with the peer, but requests the option in a maximum of 4 subsequent requests when the peer includes it in a Configure-Nak message. Acknowledges the multilink header format option if the peer requests it, but multiple classes will not be used.
Command Modes
Interface configuration
Command History
Release Modification12.2(31)SB2
This command was introduced and implemented on the Cisco 10000 series router for the PRE2.
Usage Guidelines
This command applies only to interfaces that use PPP encapsulation. Multiclass multilink PPP and PPP reliable links do not work together.
The ppp multilink multiclass command can be configured on each member link joining the bundle. For multilink groups, you can configure the command on the bundle itself (the member links inherit the configuration from the group interface).
When this command is configured (and assuming that the peer also supports and is configured for multiclass interleaving), interleaved packets are assigned sequence numbers so that they are kept in order at the receiving end. Without this command, interleaved packets are sent without multilink headers and are subject to reordering when sent over parallel links.
Pairing the local and remote keywords configures the multilink header format option when negotiating with a peer. These keywords extend the multiclass multilink PPP transmit logic to allow up to 4 transmit and receive classes, and up to 4 classes that can be negotiated with the peer. The local and remote keywords use PPP link fragmentation and interleaving (LFI) to apply multilink headers to interleaved packets. This keeps the packets in sequence when transmitted over multiple parallel links within a multilink bundle.
When the ppp multilink multiclass command is configured without the local and remote keywords, the configuration is equivalent to the following combination:
ppp multilink multiclass local request initial 2 maximum 4ppp multilink multiclass remote apply minimum 2This configuration requests two classes and the peer is sent a Configure-Nak message with a value of 2 if the option request fails.
Examples
The following example shows the configuration for a multilink bundle with up to four receive classes and at least four transmit classes:
interface multilink 9ip address 10.0.0.161 255.255.255.240ppp multilinkppp multilink interleaveppp multilink fragment delay 20ppp multilink multiclass local request maximum 4ppp multilink multiclass remote apply minimum 4no cdp enableThe following example shows the configuration for a multilink bundle that does not use multiple classes but allows the peer to request the option and transmit up to four classes when needed:
interface multilink 9ip address 10.0.0.161 255.255.255.240ppp multilinkppp multilink interleaveppp multilink fragment delay 20ppp multilink multiclass local allow maximum 4ppp multilink multiclass remote ignoreno cdp enableThe following example shows the configuration for a multilink bundle that does not use multiple classes, but allows the peer to request the option and inform the peer that the option is supported, allowing for up to four receive classes:
interface multilink 9ip address 10.0.0.161 255.255.255.240ppp multilinkppp multilink interleaveppp multilink fragment delay 20ppp multilink multiclass local request initial 1 maximum 4ppp multilink multiclass remote ignoreno cdp enableThe following example shows the configuration for multilink PPP interleaving and a maximum real-time traffic delay of 20 milliseconds on a multilink interface. Multiclass multilink PPP is then configured on a serial 0/0/1 member link and the member link is restricted to joining only the designated multilink group interface.
interface multilink 1ip address 10.2.3.4 255.255.255.0ppp multilinkppp multilink interleaveppp multilink fragment delay 20!interface serial0/0/1encapsulation pppppp authentication chapppp multilinkppp multilink multiclassppp multilink group 1The following example shows how to completely disable multiclass multilink PPP, rejecting the header and declining to allow the peer to transmit multiple classes:
interface multilink 9ip address 10.0.0.161 255.255.255.240ppp multilinkppp multilink interleaveppp multilink fragment delay 20ppp multilink multiclass local forbidppp multilink multiclass remote rejectno cdp enableRelated Commands
ppp timeout multilink lost-fragment
To set a timer that determines how long multilink PPP waits for an expected fragment to arrive before declaring it lost, use the ppp timeout multilink lost-fragment command in interface configuration mode. To reset the default value, use the no form of this command.
ppp timeout multilink lost-fragment seconds [milliseconds]
no ppp timeout multilink lost-fragment
Syntax Description
Command Default
The default value is not fixed, but is calculated based on the bundle's current reassembly buffer limit.
Command Modes
Interface configuration
Command History
Release Modification11.3
This command was introduced.
12.2(31)SB2
The command was enhanced to include the milliseconds argument on the Cisco 10000 series router.
Examples
The following example sets a 5-second wait period for receiving expected fragments before declaring the fragments lost:
ppp timeout multilink lost-fragment 5The following example sets a 300-millisecond wait period for receiving expected fragments before declaring the fragments lost:
ppp timeout multilink lost-fragment 0 300Related Commands
Feature Information for Multiclass Multilink PPP
Table 2 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Note Table 2 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.
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