I've installed a bunch of cat-5 and when I check it for continuity and polarity it seems fine, but when I hook up a pair of laptops with a x-over cord and try to ping between them, they can detect there is something on the other end but I get 100% ping failure (mixed between "hardware failures" and "timeouts"). I punched a few jacks on the end of a length of cable and that works just fine, so I know I can make good connections.
Any idea what might be causing it?
My current best guess is that it has something to do with my the wires being bundled together. How tight can you bundle cat-5 without causing problems?
What it turned out to be:
In short: bad test equipment.
The long version: I borrowed some a better tester and it said that all of the cable was good but I still couldn't get data through it. So I yanked the shortest segment out of the wall (man I love nice spacious attics), re-terminated it and brought it to a guy with a better cable tester and even it said I was doing things right (or at least I was enough of the time that I shouldn't be seeing the failure rate I was). Then I tested the patch cords I was using to do the test… Bingo! They were bad. After getting a known good replacement (and disposing of the old one with extreme prejudice) everything works.
I still don't know why the patch cords consistently worked on a few ports and none of the others but I now have tested everything in the wall and it all works!
Best Answer
You don't say how you've bundled them together. Did you use zip ties and pull them tight? Did you loop the cable and cinch the loop (like a figure eight)? Are there any other places where there are sharp bends? How small is the radius of the loops or bends?
You don't say whether they're pulled through walls or drop ceilings. You don't say what the conditions are that you're working in. Stray nail tips and sheet metal edges, etc. Are you running parallel to any fluorescent lights?
Besides squirrels and rats (which can be very real problems), most of the time it's rough handling or improper termination that cause problems.
You say "I punched a few jacks on the end of a length of cable". I presume that's just an imprecise way of saying "I punched one jack at each end of a length of cable" because you can't punch a few jacks on a cable for networking and get away with it like you might for multiple phone jacks on one cable.
Also, continuity and "polarity" mean essentially nothing. Your test with two computers or a computer and a switch or best-bet rent a proper Cat 5 or greater tester will be the only ways to approach testing. Lots of things conduct current that won't work for networks.
Also, don't trust patch cables. Try another one.