Question Strange issue: network cable not detected by either router nor computer, but passes test

llorban · Oct 2, 2024

I have an unusual problem and wondered what the experts think here. I have a TP Link router, a 200 ft of cat8 cable, and a server with 4 ethernet connectors. When the server is turned on, and the cable is plugged in on both ends, neither the server nor the router can detect that the cable is plugged in. However, when using a network cable tester, everything seems fine and the tester indicates the cable as functional. Any tips on what could cause such an issue?

In2Photos · Oct 2, 2024

Is this a Windows machine? Do you see the 4 ports in both device manager and network adapters?

llorban · Oct 2, 2024

No OS installed yet but I can see all 4 ports using FreeBSD and Ubuntu installers.

ch33zw1z · Oct 3, 2024

llorban said:
No OS installed yet but I can see all 4 ports using FreeBSD and Ubuntu installers.

Alright, so are the ports not working when Linux is up and running?

dave_the_nerd · Oct 3, 2024

What kind of tester? It’s very rare but it is possible to have a bad cable/crimp that passes a simple continuity test but isn’t “good enough” for the computers to negotiate a connection. The expensive Fluke type testers do data integrity checks and stuff too, but your typical $20 cable tester is just checking continuity.

I’d also “test” the NICs by plugging a laptop into each port and seeing the link light comes on. Even if the OS isn’t configured to see/use the NIC that should still work. Then at least you know the hardware is probably fine.

mindless1 · Oct 11, 2024

TP Link router seems like it is going to be a little, highly portable thing. Why not just temporarily take it over to the server and plug in a different cable to test that link, if you don't have another 200ft cable to test with?

llorban · Oct 11, 2024

Good idea, but the cable modem would have to go with it (and lots of coax cable).

The solution was to use cat6 cable. I read somewhere that cat8 has a max channel length of 100ft due to frequencies up to 2000Mhz (cat6 max at 500Mhz).

In2Photos · Oct 11, 2024

llorban said:
Good idea, but the cable modem would have to go with it (and lots of coax cable).

The solution was to use cat6 cable. I read somewhere that cat8 has a max channel length of 100ft due to frequencies up to 2000Mhz (cat6 max at 500Mhz).

The modem doesn't have to go. You're testing the link between the router and the server.

mindless1 · Oct 12, 2024

llorban said:
Good idea, but the cable modem would have to go with it (and lots of coax cable).

The solution was to use cat6 cable. I read somewhere that cat8 has a max channel length of 100ft due to frequencies up to 2000Mhz (cat6 max at 500Mhz).

The suggestion was only for a temporary test of the link between the two. No need to move the modem to test that.

What is your ~~client~~ server to router link speed? cat6 only does (up to) 10Gb. cat8 does 10Gb just as far, 100M, not 100 ft. As the speed aka frequency decreases, the allowable cable length increases.

The cat standard of the cable does not determine (at least not increase, in this case) the transmission frequency, the two devices on each end impose the max frequency limit based on what they are capable of.

cat8 does not have a max length of only 100ft, unless you are trying to do a 25Gb+ link which cat6 can't do at all. I hope I have explained this in a way that makes sense.

Category 8 Cabling Fact Sheet

Know about Category 8 Cabling standard , Cat 8 Connectors , installation and field testing requirements.

www.flukenetworks.com

Question Strange issue: network cable not detected by either router nor computer, but passes test

llorban

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Category 8 Cabling Fact Sheet

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