Multilink PPP Quick Start and Examples

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Contents

Introduction

ImageStream's Router distribution includes support for the Multilink PPP (MLPPP) datalink protocol. MLPPP aggregates multiple physical WAN links into a single multilink bundle. Data is sequenced, split, and transmitted down the individual interfaces that are members of the multilink bundle. On the receive side the information is recombined and resequenced before being passed to the network layer.
MLPPP can be used to bond together two T1 circuits into a virtual circuit with the effective bandwidth of 3Mbps. Besides from providing access to the aggregate bandwidth MLPPP can also reduce latency and jitter.

Before you Start

Be sure to have three separate IP subnets, one for the Multilink Interface network and two for the Ethernets connected to the routers. Each side of the MLPPP interface must have it's own IP address from the same IP network. Since they are on the same IP network, they will have the same netmask.
These IP network addresses are given to you by your Internet Service Provider, your leased line carrier, or by ARIN. If you do not plan to connect you network to the Internet, you can use an IP network address set aside for private use. The IP network address for private use can be found in RFC 1597.
Before you can configure MLPPP the physical interfaces must be configured. See the following chapters in the Router Install manual:

Configuration

In this example, we are going to assume the following:
  • Router A has an Ethernet IP address of 192.168.1.100 with a netmask of 255.255.255.0
  • Router A has a MLPPP IP address of 192.168.54.1 with a netmask of 255.255.255.252
  • Router B has an Ethernet IP address of 192.168.2.200 with a netmask of 255.255.255.0
  • Router B has a MLPPP IP address of 192.168.54.2 with a netmask of 255.255.255.252
  • Router A is providing Internet access to Router B.
  • The MLPPP interface is composed of WAN ports Serial0 and Serial1

The IP addresses used in this Technical Note are examples only. You will need to use an IP network given to you by your Internet Service Provider.

Router A

!
 version 2.00
!
interface Ethernet0
 ip address 192.168.1.100 255.255.255.0
!
interface Serial0
 description T1 Connection to Router B
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Serial1
 description T1 Connection to Router B
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Multilink1
 ip address 192.168.54.1 255.255.255.252
!
 ip route add default via 192.168.1.1
 ip route add 192.168.2.0/24 dev Multilink1
!
end

Router B

!
version 2.00
!
interface Ethernet0
 ip address 192.168.2.200 255.255.255.0
!
interface Serial0
 description T1 Connection to Router A
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Serial1
 description T1 Connection to Router A
 encapsulation ppp
 ppp multilink
 multilink-group 1
!
interface Multilink1
 ip address 192.168.54.2 255.255.255.252
!
 ip route add default dev Multilink1
!
end


Mulitlink Command Reference

Multilink ppp commands used in this example.

ppp multilink

Description

Enables multilink on a device using the PPP protocol.

multilink-group group_id

Description

Sets the group number of the multilink device, this number names the multilink interface which binds the group together. i.e. group 1 would be bound to Multilink1

Parameter

group_id - Identifies the multilink group this interface is part of.

Examples

multilink-group 3 - Assigns the interface to group 3
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