I have, on occasion, had need of long runs of Ethernet cable (usually CAT6). It seems simple enough, but it has hidden problems. Long runs of CAT can have hard-to-diagnose problems with ground loops and induced currents. Sometimes everything seems fine at first, and then things will intermittently be flaky. In addition, CAT cables are thick and heavy, particularly when you’re using gel-filled cables for outdoor or underground uses.
These days, you’re generally better off using multi-mode optical fiber cable. It’s not like the old days when you had to have a lot of special equipment to use fiber. You can get spools of OM3 pre-terminated outdoor armored LC cable. You have to pick the right length, as it cannot easily be spliced or terminated. The stuff is small (3mm diameter cable) and light. It is tough (but don’t kink it!). It stands up to weather and direct sun.
I ran a 500 foot length to connect my house to my studio. I direct-buried it about six inches deep for a few feet near each end, and the rest ran along a welded-wire fence. It is barely visible against the fence wire. I attached the cable to the fence with wire ties. Lots of wire ties. It has no trouble keeping up with gigabit Ethernet speeds (it’s rated at 10Gbps).
You need converters at each end. It can’t carry power, so if you have a PoE application, it won’t work. Otherwise, though, it’s cleaner, easier to handle, and far more reliable.
—2p