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The MPLS Multilink PPP Support feature ensures that MPLS Layer 3 Virtual Private Networks (VPNs) with quality of service (QoS) can be enabled for bundled links. This feature supports Multiprotocol Label Switching (MPLS) over Multilink PPP (MLP) links in the edge (provider edge [PE]-to-customer edge [CE]) or in the MPLS core (PE-to-PE and PE-to-provider [P] device).
Service providers that use relatively low-speed links can use MLP to spread traffic across them in their MPLS networks. Link fragmentation and interleaving (LFI) should be deployed in the CE-to-PE link for efficiency, where traffic uses a lower link bandwidth (less than 768 kbps). The MPLS Multilink PPP Support feature can reduce the number of Interior Gateway Protocol (IGP) adjacencies and facilitate load sharing of traffic.
Cisco Express Forwarding must be enabled.
Multiprotocol Label Switching (MPLS) must be enabled on provider edge (PE) and provider (P) devices.
Cisco Express Forwarding switching must be enabled on the interface by using the ip route-cache cef command.
The table below lists Multiprotocol Label Switching (MPLS) Layer 3 Virtual Private Network (VPN) features supported for Multilink PPP (MLP) and indicates if the feature is supported on customer edge-to-provider edge (CE-to-PE) links, PE-to-provider (P) links, and Carrier Supporting Carrier (CSC) CE-to-PE links.
|
MPLS L3 VPN Feature |
CE-to-PE Links |
PE-to-P Links |
CSC CE-to-PE Links |
|---|---|---|---|
|
Static routes |
Supported |
Not supported |
Not supported |
|
External Border Gateway Protocol (eBGP) |
Supported |
Not applicable to this configuration |
Supported |
|
Intermediate System-to-Intermediate System (IS-IS) |
Not supported |
Supported |
Not supported |
|
Open Shortest Path First (OSPF) |
Supported |
Supported |
Not supported |
|
Enhanced Interior Gateway Routing Protocol (EIGRP) |
Supported |
Supported |
Not supported |
|
Interprovider interautonomous (Inter-AS) VPNs (with Label Distribution Protocol [LDP]) |
Not applicable to this configuration |
Supported (MLP between Autonomous System Boundary Routers [ASBRs]) |
Not applicable to this configuration |
|
Inter-AS VPNs with IPv4 Label Distribution |
Not applicable to this configuration |
Supported (MLP between ASBRs) |
Not applicable to this configuration |
|
CSC VPNs (with LDP) |
Not supported |
Not applicable to this configuration |
Supported |
|
CSC VPNs with IPv4 label distribution |
Supported |
Not applicable to this configuration |
Supported |
|
External and internal BGP (eiBGP) Multipath |
Not supported |
Not supported |
Not applicable to this configuration |
|
Internal BGP (iBGP) Multipath |
Not applicable to this configuration |
Not supported |
Not applicable to this configuration |
|
eBGP Multipath |
Not supported |
Not supported |
Not supported |
The table below lists the Multiprotocol Label Switching (MPLS) quality of service (QoS) features supported for Multilink PPP (MLP) and indicates if the feature is supported on customer edge-to-provider edge (CE-to-PE) links, PE-to-provider (P) links, and Carrier Supporting Carrier (CSC) CE-to-PE links.
|
MPLS QoS Feature |
CE-to-PE Links |
PE-to-P Links |
CSC CE-to-PE Links |
|---|---|---|---|
|
Default copy of IP Precedence to EXP bits and the reverse |
Supported |
Not supported |
Not supported |
|
Set MPLS EXP bits using the modular QoS Command-Line Interface (MQC) |
Supported |
Supported |
Supported |
|
Matching on MPLS EXP using MQC |
Supported |
Supported |
Supported |
|
Low Latency Queueing (LLQ)/Class-Based Weighted Fair Queueing (CBWFQ) support |
Supported |
Supported |
Supported |
|
Weighted Random Early Detection (WRED) based on EXP bits using MQC |
Supported |
Supported |
Supported |
|
Policer with EXP bit-marking using MQC-3 action |
Supported |
Supported |
Supported |
|
Support for EXP bits in MPLS accounting |
Supported |
Supported |
Supported |
The figure below shows a typical Multiprotocol Label Switching (MPLS) network in which the provider edge (PE) device is responsible for label imposition (at ingress) and disposition (at egress) of the MPLS traffic.
In this topology, Multilink PPP (MLP) is deployed on the PE-to-customer edge (CE) links. The Virtual Private Network (VPN) routing and forwarding instance (VRF) interface is in a multilink bundle. There is no MPLS interaction with MLP; all packets coming into the MLP bundle are IP packets.
The PE-to-CE routing protocols that are supported for the MPLS Multilink PPP Support feature are external BGP (eBGP), Open Shortest Path First (OSPF), and Enhanced Interior Gateway Routing Protocol (EIGRP). Static routes are also supported between the CE and PE device.
Quality of service (QoS) features that are supported for the MPLS Multilink PPP Support feature on CE-to-PE links are link fragmentation and interleaving (LFI), header compression, policing, marking, and classification.
The figure below shows a sample topology in which Multiprotocol Label Switching (MPLS) is deployed over Multilink PPP (MLP) on provider edge-to-provider (PE-to-P) and P-to-P links. Enabling MPLS on MLP for PE-to-P links is similar to enabling MPLS on MLP for P-to-P links.
You employ MLP in the PE-to-P or P-to-P links primarily so that you can reduce the number of Interior Gateway Protocol (IGP) adjacencies and facilitate the load sharing of traffic.
In addition to requiring MLP on the PE-to-P links, the MPLS Multilink PPP Support feature requires the configuration of an IGP routing protocol and the Label Distribution Protocol (LDP).
The figure below shows a typical Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) Carrier Supporting Carrier (CSC) network where Multilink PPP (MLP) is configured on the CSC customer edge (CE)-to-provider edge (PE) links.
The MPLS Multilink PPP Support feature supports MLP between CSC-CE and CSC-PE links with the Label Distribution Protocol (LDP) or with external Border Gateway Protocol (eBGP) IPv4 label distribution. This feature also supports link fragmentation and interleaving (LFI) for an MPLS VPN CSC configuration. The figure below shows all MLP links that this feature supports for CSC configurations.
The figure below shows a typical Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) interautonomous system (Inter-AS) network where Multilink PPP (MLP) is configured on the provider edge-to-customer edge (PE-to-CE) links.
The MPLS Multilink PPP Support feature supports MLP between Autonomous System Boundary Router (ASBR) links for Inter-AS VPNs with Label Distribution Protocol (LDP) and with external Border Gateway Protocol (eBGP) IPv4 label distribution.
The tasks in this section can be performed on customer edge-to-provider edge (CE-to-PE) links, PE-to-provider (P) links, P-to-P links, and Carrier Supporting Carrier (CSC) CE-to-PE links.
Perform the following task to enable Cisco Express Forwarding. Cisco Express Forwarding is required for the forwarding of MLP traffic.
Multilink PPP requires the configuration of Cisco Express Forwarding. To find out if Cisco Express Forwarding is enabled on your device, enter theshow ip cef command. If Cisco Express Forwarding is enabled, you receive output that looks like the following:
Device# show ip cef
Prefix Next Hop Interface
10.2.61.8/24 192.168.100.1 FastEthernet1/0/0
192.168.101.1 FastEthernet6/1/0
If Cisco Express Forwarding is not enabled on your platform, the output for the show ip cef command looks like the following:
Device# show ip cef
%CEF not running
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
ip cef Example: |
Enables Cisco Express Forwarding. |
|
Step 4 |
exit Example: |
Returns to privileged EXEC mode. |
Perform this task to create a multilink bundle for the MPLS Multilink PPP Support feature. This multilink bundle can reduce the number of Interior Gateway Protocol (IGP) adjacencies and facilitate load sharing of traffic.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
interface multilink group-number Example: |
Creates a multilink bundle and enters multilink interface configuration mode.
|
|
Step 4 |
ip address address mask [secondary] Example: |
Sets a primary or secondary IP address for an interface.
This command is used to assign an IP address to the multilink interface. |
|
Step 5 |
encapsulation encapsulation-type Example: |
Sets the encapsulation method as PPP to be used by the interface.
|
|
Step 6 |
ppp multilink Example: |
Enables MLP on an interface. |
|
Step 7 |
end Example: |
Returns to privileged EXEC mode. |
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
controller {t1 | e1 } slot/port Example: |
Configures a T1 or E1 controller and enters controller configuration mode.
|
|
Step 4 |
channel-group channel-number timeslots range Example: |
Defines the time slots that belong to each T1 or E1 circuit.
|
|
Step 5 |
exit Example: |
Returns to global configuration mode. |
|
Step 6 |
interface serial slot/subslot/port[.subinterface] Example: |
Configures a serial interface and enters interface configuration mode. |
|
Step 7 |
ip route-cache [cef] Example: |
Controls the use of switching methods for forwarding IP packets.
|
|
Step 8 |
no ip address Example: |
Removes any specified IP address. |
|
Step 9 |
keepalive [period [retries]] Example: |
Enables keepalive packets and specifies the number of times that the Cisco software tries to send keepalive packets without a response before bringing down the interface or before bringing the tunnel protocol down for a specific interface.
If you are using this command with a tunnel interface, the command specifies the number of times that the device continues to send keepalive packets without a response before bringing the tunnel interface protocol down. |
|
Step 10 |
encapsulation encapsulation-type Example: |
Sets the encapsulation method used by the interface.
|
|
Step 11 |
ppp multilink group group-number Example: |
Restricts a physical link to join only one designated multilink group interface.
|
|
Step 12 |
ppp multilink Example: |
Enables MLP on the interface. |
|
Step 13 |
ppp authentication chap Example: |
(Optional) Enables Challenge Handshake Authentication Protocol (CHAP) authentication on the serial interface. |
|
Step 14 |
end Example: |
Returns to privileged EXEC mode. |
Perform this task to disable PPP multilink fragmentation. PPP multilink fragmentation is enabled by default.
Enabling fragmentation reduces the delay latency among bundle links, but adds some load to the CPU. Disabling fragmentation might produce better throughput.
If your data traffic is consistently of a similar size, we recommend disabling fragmentation. In this case, the benefits of fragmentation can be outweighed by the added load on the CPU.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
interface type number Example: |
Configures an interface type and enters interface configuration mode.
|
|
Step 4 |
ppp multilink fragmentation disable Example: |
Disables packet fragmentation. |
|
Step 5 |
end Example: |
Returns to privileged EXEC mode. |
|
Step 1 |
enable Enables privileged EXEC mode. Enter your password if prompted. Example: |
|
Step 2 |
show ip interface brief Verifies logical and physical Multilink PPP (MLP) interfaces. Example: |
|
Step 3 |
show ppp multilink Verifies that you have created a multilink bundle. Example: |
|
Step 4 |
show ppp multilink interface interface-bundle Displays information about a specific MLP interface. Example: |
|
Step 5 |
show interface type number Displays information about serial interfaces in your configuration. Example:You can also use the show interface command to display information about the multilink interface: Example: |
|
Step 6 |
show mpls forwarding-table Displays contents of the Multiprotocol Label Switching (MPLS) Label Forwarding Information Base (LFIB). Look for information on multilink interfaces associated with a point2point next hop. Example:Use the show ip bgp vpnv4 command to display VPN address information from the Border Gateway Protocol (BGP) table. Example: |
|
Step 7 |
exit Returns to user EXEC mode. Example: |
The following example shows how to configure for Multiprotocol Label Switching (MPLS) Carrier Supporting Carrier (CSC) provider edge (PE) device.
!
mpls label protocol ldp
ip cef
ip vrf vpn2
rd 200:1
route-target export 200:1
route-target import 200:1
!
!
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1
interface Multilink1
ip vrf forwarding vpn2
ip address 10.35.0.2 255.0.0.0
no peer neighbor-route
load-interval 30
ppp multilink
ppp multilink interleave
ppp multilink group 1
!
!
router ospf 200
log-adjacency-changes
auto-cost reference-bandwidth 1000
redistribute connected subnets
passive-interface Multilink1
network 10.0.0.7 0.0.0.0 area 200
network 10.31.0.0 0.255.255.255 area 200
!
!
router bgp 200
no bgp default ipv4-unicast
bgp log-neighbor-changes
neighbor 10.0.0.11 remote-as 200
neighbor 10.0.0.11 update-source Loopback0
!
address-family vpnv4
neighbor 10.0.0.11 activate
neighbor 10.0.0.11 send-community extended
bgp scan-time import 5
exit-address-family
!
address-family ipv4 vrf vpn2
redistribute connected
neighbor 10.35.0.1 remote-as 300
neighbor 10.35.0.1 activate
neighbor 10.35.0.1 as-override
neighbor 10.35.0.1 advertisement-interval 5
no auto-summary
no synchronization
exit-address-familyThe following example shows how to enable Cisco Express Forwarding for Multilink PPP (MLP) configurations:
Device> enable
Device# configure terminal
Device(config)# ip cef
The following example shows how to create a multilink bundle for the MPLS Multilink PPP Support feature:
Device(config)# interface multilink 1
Device(config-if)# ip address 10.0.0.0 10.255.255.255
Device(config-if)# encapsulation ppp
Device(config-if)# ppp chap hostname group 1
Device(config-if)# ppp multilink
Device(config-if)# ppp multilink group 1
The following example shows how to create four multilink interfaces with Cisco Express Forwarding switching and Multilink PPP (MLP) enabled. Each of the newly created interfaces is added to a multilink bundle.
interface multilink1
ip address 10.0.0.0 10.255.255.255
ppp chap hostname group 1
ppp multilink
ppp multilink group 1
no ip address
encapsulation ppp
ip route-cache cef
no keepalive
ppp multilink
ppp multilink group 1
no ip address
encapsulation ppp
ip route-cache cef
no keepalive
ppp chap hostname group 1
ppp multilink
ppp multilink group 1
no ip address
encapsulation ppp
ip route-cache cef
no keepalive
ppp chap hostname group 1
ppp multilink
ppp multilink group 1
no ip address
encapsulation ppp
ip route-cache cef
no keepalive
ppp chap hostname group 1
ppp multilink
ppp multilink group 1|
Related Topic |
Document Title |
|---|---|
|
Cisco IOS commands |
|
|
MPLS commands |
|
|
Basic MPLS VPNs |
“MPLS Virtual Private Networks” chapter in the MPLS Layer 3 VPNs Configuration Guide |
|
RFCs |
Title |
|---|---|
|
RFC 1990 |
The PPP Multilink Protocol (MP) |
|
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. |
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.|
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
MPLS Multilink PPP Support |
The MPLS Multilink PPP Support feature ensures that MPLS Layer 3 Virtual Private Networks (VPNs) with quality of service (QoS) can be enabled for bundled links. This feature supports Multiprotocol Label Switching (MPLS) over Multilink PPP (MLP) links in the edge (provider edge [PE]-to-customer edge [CE]) or in the MPLS core (PE-to-PE and PE-to-provider [P]device). |
bundle —A group of interfaces connected by parallel links between two systems that have agreed to use Multilink PPP (MLP) over those links.
CBWFQ —class-based weighted fair queueing. A queueing option that extends the standard Weighted Fair Queueing (WFQ) functionality to provide support for user-defined traffic classes.
Cisco Express Forwarding —A proprietary form of switching that optimizes network performance and scalability for networks with large and dynamic traffic patterns, such as the Internet, and for networks characterized by intensive web-based applications or interactive sessions. Although you can use Cisco Express Forwarding in any part of a network, it is designed for high-performance, highly resilient Layer 3 IP backbone switching.
EIGRP —Enhanced Interior Gateway Routing Protocol. An advanced version of the Interior Gateway Routing Protocol (IGRP) developed by Cisco. It provides superior convergence properties and operating efficiency, and combines the advantages of link-state protocols with those of distance vector protocols.
IGP —Interior Gateway Protocol. An Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), and Routing Information Protocol (RIP).
IGRP —Interior Gateway Routing Protocol. An Interior Gateway Protocol (IGP) developed by Cisco to address the issues associated with routing in large, heterogeneous networks. Compare with Enhanced Interior Gateway Routing Protocol (EIGRP).
IS-IS —Intermediate System-to-Intermediate System. An Open Systems Interconnection (OSI) link-state hierarchical routing protocol, based on DECnet Phase V routing, in which IS-IS devices exchange routing information based on a single metric to determine network topology.
LCP —Link Control Protocol. A protocol that establishes, configures, and tests data link connections for use by PPP.
LFI —ink fragmentation and interleaving. The LFI feature reduces delay on slower-speed links by breaking up large datagrams and interleaving low-delay traffic packets with the smaller packets resulting from the fragmented datagram. LFI allows reserve queues to be set up so that Real-Time Protocol (RTP) streams can be mapped into a higher priority queue in the configured weighted fair queue set.
link —One of the interfaces in a bundle.
LLQ —low latency queueing. A quality of service QoS queueing feature that provides a strict priority queue (PQ) for voice traffic and weighted fair queues for other classes of traffic. It is also called priority queueing/class-based weighted fair queueing (PQ/CBWFQ).
MLP —Multilink PPP. A method of splitting, recombining, and sequencing datagrams across multiple logical links. The use of MLP increases throughput between two sites by grouping interfaces and then load balancing packets over the grouped interfaces (called a bundle). Splitting packets at one end, sending them over the bundled interfaces, and recombining them at the other end achieves load balancing.
MQC —Modular QoS CLI. MQC is a CLI structure that allows users to create traffic polices and attach these polices to interfaces. MQC allows users to specify a traffic class independently of QoS policies.
NCP —Network Control Protocol. A series of protocols for establishing and configuring different network layer protocols (such as for AppleTalk) over PPP.
OSPF —Open Shortest Path First. A link-state, hierarchical Interior Gateway Protocol (IGP) routing algorithm proposed as a successor to Routing Information Protocol (RIP) in the Internet community. OSPF features include least-cost routing, multipath routing, and load balancing. OSPF was derived from an early version of the IS-IS protocol.
PPP —Point-to-Point Protocol. A successor to the Serial Line Interface Protocol (SLIP) that provides device-to-device and host-to-network connections over synchronous and asynchronous circuits. PPP works with several network layer protocols (such as IP, Internetwork Packet Exchange [IPX], and AppleTalk Remote Access [ARA]). PPP also has built-in security mechanisms (such as Challenge Handshake Authentication Protocol [CHAP] and Password Authentication Protocol [PAP]). PPP relies on two protocols: Link Control Protocol (LCP) and Network Control Protocol (NCP).
RIP —Routing Information Protocol. A version of Interior Gateway Protocol (IGP) that is supplied with UNIX Berkeley Standard Distribution (BSD) systems. Routing Information Protocol (RIP) is the most common IGP in the Internet. It uses hop count as a routing metric.
Virtual bundle interface —An interface that represents the master link of a bundle. It is not tied to any physical interface. Data going over the bundle is transmitted and received through the master link.
WFQ —weighted fair queueing. A congestion management algorithm that identifies conversations (in the form of traffic streams), separates packets that belong to each conversation, and ensures that capacity is shared fairly among the individual conversations. WFQ is an automatic way of stabilizing network behavior during congestion and results in improved performance and reduced retransmission.
WRED —weighted random early detection. A queueing method that ensures that high-precedence traffic has lower loss rates than other traffic during times of congestion.
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