[c-nsp] cat6 gigE

[Bill Wichers]

> We've been upgrading some of our uplinks between our edge switches to dual
> gbit rather than dual 100mbit.  Cat6 was ran but we've been having a few

Gigabit Ethernet will run fine over cat5e too, you don't really have to
run new cat6 cabling to use gigE.

> problems, right now we've been having a few problems getting them to link
> up.  We crimp the cable, put the module in the 2950G's and plug it in.  No
> link, even with the 3750G set to mdix auto but if i take that same cable
> and plug it into a 10/100 port it links fine.  We've gotten a few 2950's
> to link with out a problem but the last 2 we did have not worked. 
Figured > it was a bad crimp but recrimped it 3 times now..  I dont have
a tester so > i'm going to buy one but i was just wondering if there was
somthing
> special that needed to be done with cat6.  Were using the TIA/EIA B
wiring > scheme.

You should be using cat6 RJ45 connectors, which are distinctive due to the
fact that they hold each pair "sideways" as viewed from the end, instead
of all straight in-line. The idea is to keep the twists intact which helps
keep crosstalk low. Personally, I've found the connectors made by AMP to
work better than a lot of the cheaper ones which I think is due to their
3-prong forked crimp pin instead of the two-prongers most use.

My guess is that you have a pairing problem on crossover cables (I'm
assuming you might be using crossover cables since you mention these are
links between switches) . The usual reason I see gigE crossover cables
fail is that they're wired as "normal" crossover cables with the 1+2 pair
swapped over to pins 3+6 and vice-versa. On gigE, you are much better off
wiring the cables straight through and using auto-MDIX on the switches
since gigE needs all 4 pairs and the auto MDIX function doesn't seem to
work with crossovers wired the "normal" way.

If you DO have straight-through cables and you DO have good crimp
connections, then I would suspect maybe high levels of electrical noise
(keep the data cables away from lights and power cables as much as
possible).

Have you tried just putting the two problem switches next to each other
and using a regular patch cord between them to rule out bad switch ports
as the cause of the problem?

     -Bill

*****************************
Waveform Technology
Systems Engineer