One day before the fiber install, I upgraded Randy, the house server. I swapped its 2.5-gigabit network card for a 10-gigabit one. This felt like overkill. Then I remembered the new internet plan: 5 gigabits, symmetric. The 2.5-gigabit card would have silently capped the whole line at half speed. The pre-work paid off in one specific, stupid way. I will get to it.
Cat6 versus Cat6A
The first attempt at the 10-gigabit link did not come up at all. The port raised a “signal loss” alarm and negotiated down. The cable looked fine. The cable was fine — for a slower spec.
The cable was Cat6. A 10-gigabit link over real distance needs Cat6A. The A stands for “actually.” Cat6A has bandwidth headroom that Cat6 does not have. The two cables look identical, and one of them silently fails at 10 gigabits with no useful error. I installed Cat6A, and the link came up immediately. Write that one on your hand.
The passthrough that did not pass
Then came install day. The AT&T tech was a nice man. He ran fiber from outside, through the attic, and straight into the rack. He lit the gateway, ran a speed test from his laptop, saw five gigabits, and left. A clean install.
But my setup expects one more step. The all-in-one gateway must hand its public connection straight through to my own router. Then I do not run two stacked routers, each with its own translation layer. The passthrough did not pass. My router sat there and held a useless private address from the gateway, not the real public one. Nothing behind the router had internet, and everything was behind the router.
The visitor badge
The cause is a good one. The gateway hands the real connection to one specific device only. It identifies that device by its hardware address, a factory ID on every network port. I had registered my router’s main port.
But the fiber was plugged into a different port on the same router — the high-speed port. That port has its own, different hardware address. The gateway looked at it and did not recognize it. So the gateway gave it the digital equivalent of a visitor badge.
The correct face, on loan
The fix is sneaky, and I enjoy it. You tell the high-speed port to impersonate the registered port. You clone the old hardware address onto it. Now the gateway sees the ID it expects, and it hands over the real connection. My router got the public address within seconds. The router was always allowed in. It arrived with the wrong face, and I lent it the correct one.
When the van pulls away
The final numbers: 4.9 gigabits down, 4.77 gigabits up, six milliseconds of ping. The old cable internet became a backup line for a 30-day trust period. Then I cancelled it, after the fiber proved it would not flinch.
One rule keeps proving itself. The professional install ends when the tech’s laptop shows a good number. The actual install starts about thirty seconds after the van pulls away. That is the part where your specific setup meets the real world.