Do long gigabit (CAT6) cables easily break?

Question

I had this 30m gigabit cable which registered as a gigabit connection via my router. I noticed recently that it's now a 100 mbps connection. I tried short gigabit cables for testing and they all registered as a gigabit connection.

Maybe I mishandled the cable and one of the wires broke? I remember pulling it out with some force when I was changing routers. I guess I should just buy a new cable?

Really bugging me ever since I got a 100 mbps internet subscription. Also, I remember getting 50 MBps in my NAS transfers, now it's back to 10 MBps.

Is it common for CAT6 cables to lose their gigabit speed?

NOTE: My cable goes from one aircon opening to another, meaning that a lot is exposed to electricity and the outdoors as it travels from a room to my room.

Answer 1

UTP cables have a maximum pulling tension and bend radius. Exceeding either of those while installing can damage the cable. Also. most UTP cables are not suitable to be run outdoors unless specifically designed to do so, and getting them wet can cause permanent or intermittent failure. Also, running a cable outdoors requires it to be properly grounded Gigabit ethernet requires all four pairs to be working correctly, otherwise it can negotiate to fast ethernet.

You need to get an indoor/outdoor version to have a sheath which can get wet. Water changes the dielectric properties which high-speed ethernet depends on. Normally, running the cable outdoors is done through conduit which can itself be grounded. This is a huge subject, but lightning strikes send electricity through the surrounding air and ground, too. They can induce large electrical spikes in cables, which your sensitive equipment can't handle. Basically your cable is a long antenna.

Gigabit ethernet (1000BASE-T) requires all four pairs (1-2, 3-6, 4-5, 7-8) to be working correctly. If they are not, the standard calls for it to try to negotiate fast ethernet (100BASE-TX) or ethernet (10BASE-T). The latter two only need two pairs (1-2 and 3-6) to function.

Answer 2

Gigabit ethernet requires all four pairs to be working. Many gigabit adaptors will drop back to 100 megabit if one of the pairs that is used for gigabit but not for 100 megabit is bad.

I think the issue is less than length and more the installation method. Many plastics while seeming waterproof in the short term are not suitable for long term exposure to moisture.

If you really must run the cable on the outside then you need to use suitable outdoor rated cable.

As for grounding most ethernet cables don't have a ground connection. Ethernet interfaces are supposed to be isolated to about 1.5KV to protect against ground potential differences. For cables going between buildings in lightning prone areas ground differences may get bad enough to break stuff but I highly doubt it will be a problem for a cable that runs along an outside wall and goes back into the same building.