Monday, May 07, 2007
Why do I keep doing this to myself?
IF IT AIN'T BROKE, DON'T FIX IT!
Spring has been complaining that the DSL connection is sluggish. I did some tests and yes, there is a definite bottleneck at the DSL modem.
Now, a few months back when we (The Company) controlled both sides of the connection, it wasn't slow. But back then, I had enough public IP addresses to give both the DSL modem and my firewall (an old 486) a public address. The DSL modem just slung packets around leaving the firewall to do all the filtering and NATting.
When The Company stopped providing DSL (because of the Monopolistic Phone Company charging us about twice their rate) we went with another DSL provider (and The Company is paying for it). Now, because we only got a single public IP address, things on my network had to change. Basically, the DSL modem is now doing the filtering and NATting for my network, and it might not be able to keep up with the load.
So today I tried to fix it. Moved the public IP address to my old 486, gave the DSL modem some private IP addresses and had it route the public IP address to the 486.
It should work. The DSL modem gets the packet for the public IP address on the WAN port but the routing table in the DSL modem should then forward the packet towards my firewall.
Only it didn't work.
The Monopolistic Phone Company (which actually owns the DSLAM—the device that provides DSL) requires PPPoE with authentication (a few years ago this wasn't the case). So the DSL modem does a PPP negotiation, which, for whatever reason, sets the WAN port to the public IP address. Which is not what I want.
And the DSL modem I use doesn't do bridging, which is what I want.
Then Wlofie noticed the DSL modem supported a feature called “PPP Half Bridge,” which seems to do what I want—it forwards packets to the public IP address to a given host.
Only, the host has to use DHCP to get the public IP address, which I don't need because the public IP address I have is static.
I tried it.
It didn't work (subsequent research shows I might have set it up incorrectly—more testing is needed, but later, when I'm calmed down and not “at work”). And it took a ridiculously long time to reset the modem to a factory configuration (because once I set “PPP Half Bridge” mode, I couldn't get to the DSL modem anymore—turns out all I had to do was pull out the ADSL cable and powercycle the DSL modem, but I found that out after reconfiguring the device).