SBC/DSL+PPPoe + router: why does this work?

Factual Questions
1

I just blew a whole afternoon getting my mother’s DSL connection to work with a wireless router. I’m used to cable-style internet, so I wasn’t prepared for the problems I ran into. I finally found how to get it working, but I’m wondering why it now works – and if it will continue to work.

Background:

  • The internet connection is SBC/Yahoo DSL with a SpeedStream 5100 modem.
  • One computer had previously been connected sans router, which worked fine.
  • We added a NetGear WGT624 wireless router, which didn’t work fine.

I googled, and found suggestions (and I’m having problems re-finding the those suggestions via Google, I’ll repost them later) to the effect that:

  • The SBC/DSL modem is using PPPoE, not DHCP, which is apparently the root problem. You can’t treat this like a cable internet connection.
  • The Solution is to configure the modem to use Bridged mode, then configure the router to use PPPoE and log into the DSL modem using the account+password of the DSL account.

This solution made sense: the router emulates a single PPPoE client, logs into the modem as the authorized user, then serves IP packets from/to the modem as if it were a single computer. Which was fine in theory, but it didn’t work for beans.

After much headbanging and rebooting, I finally logged into the Netgear support forum (where I should have looked in the first place :smack: ), and got these instructions for connecting the WGT624 to a SpeedStream DSL modem. In summary:

  • Configure the modem normally (i.e. PPPoE in the modem as if a single user were connecting).
  • Set the router to use a fixed DNS lookup of 4.2.2.2 and 4.2.2.1.

It worked!! I connected 3 computers to the Netgear router, one wired, two wireless. It was all good. Question: Why did this work? Why does this magic-DNS (4.2.2.2?!?) solve the problem? Will this continue to work? :confused:

2

Interesting. I have almost the same setup - a SpeedStream and a WGR614. I didn’t have to set the DNS, but had to do the rest as you describe. It’s been at least 8 months now, with only one problem (my connection cut out at 4 in the morning; after sleeping, it was back on).

Don’t know why 4.2.2.2 should work, although I’d be interested in finding out. Perhaps it’s just SBC’s server configuration?

3

The DNS has nothign to do with it. You could have left that unconfigured, or set it to any other public DNS server on the net. The critical point is that the first device downstream of the DSL modem must log on with PPOE.

4

LSLGuy, please re-read the OP.:

  • The DSL modem was configured to be the PPPoE logger-onner. Nothing downstream was logging on. That had been tried, and didn’t work.

  • The setup did not work until the “magic” DNS (4.2.2.2) was entered in the router.

  • The instructions to use that “magic” DNS came from the router manufacturer, see link to the Netgear knowledge base, above.

5

Further thoughts:

4.2.2.2 doesn’t seem to be a “magic” IP address, it’s a real server, according to this: vnsc-pri.sys.gtei.net. Apparently the router needed some DNS address, anything, because the PPPoE connection wasn’t supplying one.

Which I guess begs the question: why does it work when you plug a computer directly into the DSL modem – the computer picks up some DNS address, I assume via DHCP from the modem, and everything just works. Why would the router not benefit from the process?