Tom Limoncelli wrote: > On Thu, Feb 4, 2010 at 12:37 PM, Nick Whalen > <ni...@mindstorm-networks.net> wrote: > >> seph wrote: >> >>>> 1. 10M ethernet is half-duplex. >>>> >>>> >>> Er, really? That's not my recollection. (And the first couple google >>> hits tell me full duplex was supported on 10BaseT) >>> >>> Generally though, I'd expect it to work. The nbx100 phones (proprietary >>> voip) were only 10M devices for a long time. As long as you're not >>> chaining much through their internal switch ports. >>> >>> >> Yeah 10BT supported FD, however IIRC, back in those days the Cisco >> switches (1900 series Catalysts) had issues with 10BT/FD. Maybe that's >> what Tom's remembering? :) >> > > 10BT was HD originally (before switches existed, we only had HD hubs, > remember?). The FD version was never widely adopted because 100BT was > available then. I don't think I ever had a machine that was 10BT FD > if I recall correctly; what I read about them was that no two vendors > inter-operated very well. > > Tom > > 10BaseT-FD auto-negotiation was poor at best. Some manufacturers (including $WORK which is mentioned above :-) assumed HD and negotiated to FD, others did the reverse. And the test logic was just plain bad in some implementations, so that you end up with one end in HD and the other in FD, or no connection at all. This continued to be a problem at 100 Mb, but was much worse with 10 Mb.
If you use 10BaseT, set the duplex manually, don't rely on autonegotiation. FD may have some crosstalk problems on poor CAT-3, but should work fine on decent, properly terminated CAT-3. If there are R-66 blocks in the middle of a run between the phone and the switch, all bets are off. Make sure to clean up all of the terminations to 10BaseT standards, keep the removal of jackets tight, keep the twists going properly outside the jackets at the terminations. Length is going to be important, and depending on the cable characteristics you may either find yourself extremely limited in length, or able to 'push' to limits beyond the specs. The label 'CAT-3' got applied to just about any non-CAT-5 cable, and there are wide variations in characteristics. One thing in your favour, since you are installing modern gear, the 10BaseT tolerance seems to be better in new chip sets - making ports work at 100 Mb or 1 Gb has made 10 Mb 'trivial'. By now, at least any two ports with the duplex set manually should run at 10 Mb FD, but that was not always the case. SIP phones are just fine on HD, but heed the warning about hubs - you don't want too many phones sharing the same switch port. You might be able to run a half dozen phones on a hub going to the switch port, but much more and you could get into trouble. I haven't pushed this limit, so definitely do some testing if you are stuck with hubs. I highly recommend dedicated switch ports for reliability. - Richard _______________________________________________ Discuss mailing list Discuss@lopsa.org http://lopsa.org/cgi-bin/mailman/listinfo/discuss This list provided by the League of Professional System Administrators http://lopsa.org/
