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Mostly about computers, generally Linux-related

PPPoE, the Router, Wireless Internet, and TTL

Most dorms from the complex I live in have switched to PPPoE; better means of monitoring us I heard, but I won’t bring it up seriously. Of course, the network administrator in my dorm refused to switch, for fear he’d lose (perceived?) control. Quality started to drop, culminating with up to a second ping reply and a quarter lost packets. People screamed everywhere, and I myself was not happy — cormyr had just arrived and there I was without a source of up-to-date packages. Just so you can picture it, the Gentoo mirror I am using is (to my knowledge) literally less than a kilometer away, in the Rectorat building of University ‘Politehnica’ of Bucharest, a place I can see from my window. From there, I downloaded with less than 30 kilobytes per second.

Away from this near uprise, a few dorms distance, I was helping Roxi install Gentoo. She had switched to PPPoE, which caused a total of nearly 4 hours of tinkering with the connection. The live CD contained a script whch helped, but when the install was complete, we were stranded; luckily, she dual booted to XP, so we could search for solutions, download packages, and use a memory stick to transfer to Gentoo. Finally having got things working, I admit I never would have thought of the remedy by myself: the PPPoE interface had to manually be set to MTU 1492. We also had great trouble setting the routes, but that was really something we could handle.

Meanwhile, finally giving in to the increasingly furious dorm-mates, our admin finally made the switch to PPPoE. “Hah, I’ve been through this already”, I thought, but boy, was I wrong. To top things off, that exact same day I got a wireless router, so me and my roommates can use our laptops around our room. Two problems, one of which was completely new, the other only mildly and largely unsuccessfully previously tackled.

First, I sloppily got my connection working. Sloppily, because for the next few days I constantly forgot to set my routes right, which always caused great confusion. After that, I realsied I probably didn’t need that, because I wanted to connect tot the Internet through my new router. Which thankfully knew PPPoE. But again, things were far from over.

Packets get to us with TTL=1; it’s a pointless measure in my view, but it seems to be common practice in the complex where I live. The D-Link DI-524 (with which I am utterly dissatisfied) has an option called “Do not change TTL value”, but it apparently doesn’t work. It connected fine via PPPoE, I pinged Google via its HTTP interface, but this is where things ended. The solution (a cludge, if you ask me) was to connect to router to my desktop (newguy) and use that as a router that sets TTL via iptables. So I have newguy acting as a router for a wireless router. At least I have wireless, but only while newguy is on.

Bottom line is that, between paranoid admins and cheap, non-OpenWRT-supported hardware, we have another glorious bundle of wires and newguy has another glorious bunch of scripts which I only marginally understand.

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March 15, 2008 - Posted by | linux

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