Using a Netgear DG834Gv3 as an ADSL modem

Last week I treated myself to a new NAS device (cost: £££; good backups: priceless) which also has a built-in 802.11N wireless access point. Consequently I needed to find a way to make my Netgear DG834Gv3 act as a pure ADSL modem to avoid the headache of two layers of NAT.

While not documented/officially supported, the Netgear can be used as a pure modem (sometimes called “Bridge-only Mode” by other vendors) using a hidden link and selecting “modem-only” mode:

This was trivial to find using the leading search engine, but it does not work using the default settings in the UK—you must also change the ADSL multiplex method to “LLC” on the “ADSL Settings” page1. Having done this, connect the second wireless AP/router/computer to the Netgear via ethernet and configure it to connect to the Internet using PPPoE.

  1. Confusingly this is the opposite to the standard setting used when configuring UK ADSL which would normally be VC-based multiplexing []

Netgear DG834Gv3, iChat and Linux

I recently picked up a Netgear DG834Gv3 wireless router and modem on ebay for a very reasonable price. In order to make iChat video conferences work seamlessly (i.e. without having to configure port forwarding) I had to:

  1. Upgrade it to the latest firmware (V4.01.30).
  2. Toggle UPnP off and on (twice according to some forums).
  3. Disable port scan and DOS protection (Advanced WAN Setup).
  4. Disable SIP ALG (Advanced WAN Setup).

Although my Macbook was now very happy, the Ubuntu box would not connect to the wireless network using WPA encryption: SoftMAC authentication would complete, but the wireless NIC could not see any packets. The web suggests that PS3 owners have also experienced problems after upgrading to 4.01.30 and the only answer is to downgrade, 4.01.20 being the last known “good” version. Sadly Netgear have removed all but the new broken and a very old versions of the firmware from their support page, but the source code is still available and the tar.bz2 contains a pre-built image so you don’t even need to compile it.

At this point I am back to square one since iChat will no longer receive incoming video requests from people behind NAT devices unless I use manual port forwarding.

Firmware 4.01.37 has been released. I have not tested this but it claims to fix the incompatibility with the Playstation3 so hopefully it should also work with Linux machines.