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Re: [Astlinux-users] Connecting topology
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From: Kristian K. <kri...@gm...> - 2007-01-02 09:01:54
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On 1/1/07, Phil McKerracher <ph...@mc...> wrote: > Happy New Year everybody, and thanks for all your replies to my earlier query on this subject on the old mailing list. > > I've held off replying while I did a bit more research about using astlinux as a router, to avoid making a complete fool of myself in public. But I still don't understand it all, so here goes anyway. :-) > > I've got no problem with throttling my external connection to 90% of the available bandwidth to avoid queueing problems. Obviously it would be nice to have a system that copes with congestion without configuration, but I can live with it. > > I've discovered elsewhere that the net4801 won't cope with 100 Mbit/s ethernet routing (between PCs on my SoHo LAN) but should cope with my 4 Mbit/s internet connection OK. This is as I suspected, although it does make me wonder why my (much cheaper!) Netgear router copes with it all right - presumably it contains special hardware. This in turn makes me wonder whether the net4801 was a good choice of hardware for this sort of thing. Anyway, I think I can avoid all the speed problems by simply connecting my Netgear router downstream from the astlinux box, with my PCs connected to the router and my phones to the astlinux box. It's twice as much cable but what the heck. The net4801 can ROUTE at about 40 mbit/sec between interfaces. That's pretty good. Chances are your Netgear can't get anywhere close to that. However, your Netgear probably also has a layer two switch built in. Switches have ASICs to do simple ethernet switching at wire speed - 100 mbit/sec. Comparing the throughput of a router to a dumb switch is nowhere near a fair fight... Do a speed test with the Netgear routing - from the "Internet" interface to any port on the switch and see how fast it is... > I'm a bit puzzled that PBX-only mode is now the default, since that implies no traffic shaping, which I would have thought would guarantee problems whenever a big download or upload was in progress. What do people do in this situation? Use a separate internet connection? Or a clever router? PBX-Only is the default in terms of configuration but all of the functionality is still there. All you have to do is make sure the box has two ethernet adapters (your net4801 has three), and uncomment INTIF in rc.conf. Now you are in router mode. To activate traffic shaping, simply define EXTUP and EXTDOWN. > Anyway, I now want to enable the other ethernet ports on my box, and it's not obvious how to do this from reading rc.conf. My net4801 has seven ports (which now looks like a mistake). Assuming I was happy with slower speeds I still don't see how I can configure the unit to connect several phones or PCs to it. Is there a hidden assumption here that I'm missing, that an external router is always used? In PBX-only mode the phones connect to the EXTERNAL interface (the only one active by default), right? So the asterisk box is just another device on the internal LAN, rather than being physically connected between the phones and the external internet as I had assumed. If so, then I think I need to buy yet another router. :-( If your net4801 has seven ports you must have added the four port ethernet adapter. That's great, except that (like I mentioned above), you will never see the same level of performance from this sollution. Even IF you were to bridge the ports together to act like a switch, the speed would be nowhere near wire speed on your net4801: http://facweb.cti.depaul.edu/jyu/Publications/Yu-Linux-TSM2004.pdf As you can see, these tests were conducted with a 1.2ghz Duron processor with TWO ethernet ports. Your 266mhz Geode has seven :). > I hope this is all clear. Maybe a couple of diagrams would help: > > 1. This is how I originally expected to connect things: > __________ > | |----IP Phone > INTERNET---| astlinux |----IP Phone ... > | box |----Computer > |__________|----Computer ... > > 2. I now think PBX-only mode is meant to be connected like this: > ________ > | Router |----IP Phone > | |----IP Phone ... > INTERNET---| | __________ > | |---| astlinux | > | | | box | > |________| |__________| > > 3. And this is how I now think the PCs should be connected: > ________ > | Router |----IP Phone > | |----IP Phone > INTERNET---| | __________ ________ > | |---| astlinux |----| Fast |----Computer > | | | box | | Router |----Computer ... > |________| |__________| |________| > > Does that make sense? > > -- > Phil McKerracher > www.mckerracher.net > Phil, Your best bet is to connect your internet connection to eth0 and connect a switch (not a router) to eth1 and then connect all of your local devices to the switch. -- Kristian Kielhofner |
