100mb != gbit. :)
We run gbit over cat5e and approaching 100 meter runs without
any issues, so I would look closely at terminations and
interference. And also at the interfaces at either end. Are
they set right? If one end is a pc, is it using the right
drivers, are they configured correctly? Is the other end gbit
capable? Is there a 10/100 switch or hub forgotten in the
middle that isn't?
Also, check link speeds rather than throughput. "not giving
Mbit speeds" could mean you're assuming 1 gigabyte of data per
second rather than the typical 1/10th of that, with a
following wind and no other traffic on the network, AND that
the kit either end is capable. (Hint, many user grade switches
can do a 1mbit link, but can't sustain megabit data flow -
they just don't have the processing power)
Cat6 is a sod to work with, but will help with interference
issues to a degree if done properly. Don't just assume it's the
same as cat5e to work with, though. I'm almost certain that in a
home environment, you're better off re-using the existing cat5,
or running new cat5e away from mains/noisy areas. IME, most cat6
use cases are more cost effectively done with cat5e, which costs
buttons.
