Windows – Do I need a cross-over cable

These handheld devices are useful, since they test the cabling on the physical level and can help discover problems (cross-talk, wrong impedance, etc.) which are difficult to diagnose otherwise.

If you pulled some cable too much, or some turn inside your wall is too sharp, your network will "kinda work", but you won't get maximum throughput, or you'll get weird connectivity issues, etc.

It will be a pain to re-do stuff once you make everything neat and declare the job is done. Maybe you can lease such a device or hire someone who have it to test your network? These testers are prohibitively expensive to buy if you need it for just one job...

So, it is not strictly necessary to test with such tester, but it gives an extra assurance you did things right, especially if you're not a pro in network cabling.

Almost all recent network cards support auto-crossover (Auto-MDIX). With this feature, whether a cable is normal or crossover doesn't matter - you can connect two computers using a normal cable, so although I have not tested it I'm quite sure it would also allow connecting such a card to a router using a crossover cable.

If this feature is not supported by your network card, you'll have to use a 'normal' cable.