Accessing your ADSL modem In Bridge Mode

Introduction

Gargoyle supports PPPoE connections over ADSL links. ADSL links use phone lines as there physical connection to the internet. The phone line requires special modem equipment on both ends and filters to allow the line to be simultaneously used as a phone connection. Gargoyle does not support PPPoA connections directly.

For those of you that have PPPoE connections and want to deploy a Gargoyle router you would be wise to pay attention to the configuration of your ADSL device. Most of these devices can be configured as routers themselves but since you are using Gargoyle it is best if you change the configuration the into a simple modem. The name of this mode varies by manufacturer. The term “bridged mode” seems the most common but something like “modem mode” or “simple ADSL modem” may also be used. Changes to these devices are typically made through a web page you can access using the modem's IP address.

There are several reasons to configure your modem in this fashion. First the performance of Gargoyle's QoS will be improved since it will account for PPPoE overhead leading to more accurate control. Second your ADSL Router becomes transparent and your Gargoyle router will obtain your WAN (wide area network) IP address directly. This is useful should you need to port forward or remotely gain access to your network from the internet.

The three things that need to be done.

  1. Configure your modem with a fixed IP address which is not on the subnet used by your LAN. For example if you LAN devices are in the 192.168.1.x subnet then give your modem the fixed IP 192.168.2.1,
  2. If possible enable DHCP on you modem. In most of these devices DHCP can be active in modem mode although sometimes it is necessary to configure it before you change modes.
  3. Change the mode of the modem to the “bridge mode”.

Since all routers are different you will need to do some research to figure out how to navigate the screens on your modem to accomplish the above. But if you are able to do these no further work is needed on your part and after resetting your router you will be able to access the modem from your LAN using the fixed IP address you gave it.

If you are unable to get DHCP to work on your modem in 'bridged' mode you can read further on how to manually configure your router to overcome this issue.

Steps to manually configure modem access

For most people the above introduction section is all you need to read to properly configure your router. However, if you cannot get the DHCP server on your modem to function in 'bridge mode' you can manually configure this function.

To continue further you will need the following

  • PPPoE connection (PPPoA is not suitable)
  • Suitable xDSL modem (Netgear DG834)
  • Gargole Router with SSH access enabled
  • WinSCP or other means to edit a file on your router

Setup

ADSL Modem Setup

First set up your ADSL modem

Netgear DG834 example

Change the router IP address to 192.168.10.1

Then follow these instructions

http://vpncasestudy.com/download/DG/DG834_Tips100.pdf

NOTE Once in 'Modem only' mode the DG834 will act as a simply modem, its IP address will have no relevance except for connecting to the router to change settings or reconfigure. Remember this IP address, as DHCP will no longer function and you will need it if you wish to connect to the DG834 in future.

Manually Configuring your Gargoyle router

Locate the following file on your router. /etc/ppp/ip-up.d/modemaccess.sh

In the file find and uncomment the line with the define for 'ROUTER_IP' in it. Edit the IP address such that it is an address which is in the same subnet as the fixed IP address you gave your router. For example if your modem is 192.168.10.1 then make this line 192.168.10.2.

#This script allows access to the ADSL modem web interface when pppoe is used.
#For this to work configure your modem in brdige mode with DHCP enabled on the modem.
#This will cause the modem to dish an address to the router interface when requested below.
#
#Alternatively you can manually set the below variable ROUTER_IP with the IP address
#you want to use. Make sure the IP address is on the same network as the modem.
#ROUTER_IP=10.0.0.2

Edit and Change

#ROUTER_IP=10.0.0.2
to
ROUTER_IP=192.168.10.2

Save the file, reboot your Gargoyle router and you should be able to access the modem at its IP address using your web browser.

ADSL Modem Access

You should now be able to access your adsl modem via http://192.168.10.1

adsl_modem.txt · Last modified: 2013/05/21 16:03 by eric
 
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