Access To Modem Configuration

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Revision as of 06:33, 29 March 2010 by Ikonst (Talk | contribs)
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Case of a Bridged modem


In this case the router itself creates the PPPoE connection to the ISP server; but to work, the connection between the modem and the router must have an IP address. Usually the modem gives an address to the client; but this address will never be used except to access the configuration interface of the modem.

My modem is a Speedtouch 510, is IP address is and it gives the address to the device connected to it. The easiest way to know these addresses is to connect the modem directly to your computer and take a look at your network card configuration. The default gateway is the Modem address and the Card address is the one provided by the modem. It should be noted that a lot of modems come preconfigured to use the 192.168.1.x IP range. This will need to be changed for this to work.

So it looks like this.

By default if you type the IP address of the modem you have an "Impossible to contact the server" error.

The way to follow

  • Go to Administration -> Commands
  • Enter
ifconfig $(nvram get wan_ifname) netmask

and click on Save Startup

  • Enter
/usr/sbin/iptables -t nat -I POSTROUTING 1 -o $(nvram get wan_ifname) -j MASQUERADE

and click on Save Firewall


  1. The IP address (in the example, should be different from the IP address used by your modem. For example, if your modem uses the address, the IP address will be good.
    • A "cleaner" solution is to use DHCP, but this is out of the scope of this tutorial.
  2. $(nvram get wan_ifname) gets the WAN port of your router automatically. If you wish to enter it manually, you should use the following command to get your WAN interface name:
 nvram get wan_ifname

Alternative way

A alternative (and cleaner) way to execute the above commands on startup is the following:

  • Log in via ssh (or telnet)
  • create a file with the following content:
ifconfig $(nvram get wan_ifname) netmask
  • save it as "/jffs/etc/config/modem.startup"
  • create another file with the following content:
/usr/sbin/iptables -t nat -I POSTROUTING 1 -o $(nvram get wan_ifname) -j MASQUERADE
  • save it as "/jffs/etc/config/modem.wanup"
  • make them executables:
chmod +x /jffs/etc/config/modem.*