How to test/debug bad network wiring?
Don't run CAT6 cable
If the bends in your cable don't exceed the minimum bend radius for the cable type then it's not an issue.
If the cable lengths don't exceed the maximum cable length (in your case 100 meters/328 feet) then it's not an issue.
Why run new wiring when you can simply test the existing cable (not the terminations but the cable itself) and then reterminate one or both ends.
EDIT:
Considering there is so much contention on this, I've updated the answer:
There are two basic options here:
- Rewire. As mentioned above, if you can't be certain all the existing cabling is worth reusing, you may be better off starting from scratch. Hiring a contractor that will run everything, and certify the runs is certainly easier, but maybe not cheaper.
- Fix the problems with the existing cabling. Here you must check each cable run for shorts, and each end for proper termination, ensure the cables are run within specification, and within the specified bend radius. You should also determine if Plenium cabling has been run (if required). You should get a good cable tester/certifier, and check all the work after it has been corrected.
There is a cost/benefit tradeoff on either option. If you choose to go with the rewire, I personally see no reason to run older standards, unless the cost is truly too great to run CAT6a.
Last night I decided to reterminate the obviously bad ends in the wiring closet just to see what would happen (and because I haven't done my own cables in a few years and figured even if it did nothing I could use the practice). After reterminating I can get link on all ports. So seemingly they somehow managed to do everything OK except royally screwing up the network closet. I don't understand why my cable tester showed zero signal before, perhaps they had not crimped them tightly enough to get a good contact, used bad RJ45 connectors, or maybe my $6 cable tester was priced at that for a reason.
I'm accepting joeqwerty's answer because his advice re reterminating and testing before rewiring was sound. I'm still pretty skeptical of the cabling work, given the total newb errors in the terminating, and if I have troubles in the future I will likely rewire with 6a for 10 gigE so definitely a +1 for Cheekaleaks's answer as well. I don't really need 10 gigE, but the extra cost of 6a vs 5e pales in comparison to my labor input in rewiring, so a new 5e install wouldn't make sense here.
Thank you both for your responses.