Allied Telesis L2TP Tunnel User Manual

AlliedWare™ OS

How To |

Configure Dynamic Routing Over An L2TP Tunnel

Introduction

This How To Note shows an example of using a dynamic routing protocol over an L2TP
tunnel.

Running dynamic routing protocols over a secure Internet connection can be a complex
issue, with the possibility of intermittent connections causing routing problems.

OSPF (or BGP) are more connection-oriented than RIP and therefore are more susceptible
to problems caused by intermittent loss of connection between 'neighbours'. A neighbour
that may bounce up and down can cause havoc to the correct propagation of OSPF routing
information for a network.

The following example scenario is for setting up RIP over an L2TP tunnel. RIP is simpler and
has less overhead and control, so it provides a more robust setup as a dynamic routing
protocol over an L2TP tunnel.

Which products does it apply to?

This Note applies to the following Allied Telesis routers, running software version 2.6.1 or
later:

z AR400 series

z AR700 series

C613-16037-00 REV C

www.alliedtelesis.com

An example scenario for RIP over L2TP

rip-l2tp.eps

Related How To Notes

You may also find the following How To Notes useful:

z How To Configure Remote L2TP Tunnels

z How To Configure Allied Telesis and Cisco Routers To Interoperate Over L2TP

How To Notes are available from www.alliedtelesis.com/resources/literature/howto.aspx.

An example scenario for RIP over L2TP

Our example uses two office sites that are connected via a WAN connection over the
Internet using an L2TP tunnel for security.

The setup (shown below) shows the 'Central office' and 'Remote office' routers connected,
in this case, back to back via their Ethernet interfaces (this would likely be the remote WAN
connection across the Internet, with perhaps static IP assignment from the ISPs).

RIP propogates
VLAN OSPF
routes over
L2TP tunnel
to remote router

Central office router

POWER

192.168.1.1

PPP0 over
L2TP tunnel

192.168.2.1

POWER

Remote office router

OSPF used on
local VLAN
networks

ETH0

X PC

HUB

Eth0 IP=10.10.10.1

WAN

Eth0 IP=10.10.10.2

X PC

ETH0

HUB

OSPF used on
local VLAN
networks

VLAN 2 IP=222.222.2.1

VLAN 1 IP=222.222.1.1

VLAN 1 IP=200.200.1.1

VLAN 2 IP=200.200.2.1

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