FAQ
TL;DR: Replacing a 20 m cheap CCA “Cat 5e” with real copper Cat 6a raised Speedtest throughput from 85 Mb/s to 520 Mb/s; “Good cables cost money” [Elektroda, Zutket, post #17546886] Use solid-copper UTP, crimp with quality tools, and verify Gigabit link lights.
Why it matters: The wrong cable instantly throttles a 500 Mb/s line to old-school Fast-Ethernet.
Quick Facts
• Gigabit Ethernet supports 100 m channel length over Cat 5e or better [TIA-568-C.2].
• Copper-Clad Aluminum adds ≈53 % resistance vs. pure copper, increasing errors [Fluke, 2020].
• Cat 6a handles 10 Gb/s at 100 m; Cat 5e tops out at 1 Gb/s [TIA-568-C.2].
• 37 % of field link failures trace back to bad patch cords [Fluke, 2021].
• Sub-€5 crimpers often mis-seat pins 1 & 8, cutting speed to 85 Mb/s [Elektroda, peePeer, post #17552529]
Why did my Gigabit NIC drop to 100 Mb/s on a 20 m run?
One or more pairs were open or poorly crimped, so the port fell back to Fast-Ethernet, which uses only two pairs [Elektroda, peePeer, post #17552058]
How can I spot a copper-clad aluminum (CCA) patch cord?
Scrape the conductor; a silver core with a thin copper skin reveals CCA. The cable also weighs about 30 % less than solid copper of the same length [Fluke, 2020].
Does cable length alone reduce speed on Gigabit Ethernet?
No. Any solid-copper Cat 5e/6 link up to 100 m maintains 1 Gb/s when correctly terminated [TIA-568-C.2].
UTP or shielded cable inside skirting boards?
Use UTP. Shielding requires bonding at both ends; otherwise it can act as an antenna and worsen noise [Elektroda, jprzedworski, post #17552118]
Cat 5e vs. Cat 6a—worth the upgrade?
Cat 6a supports 10 Gb/s, so one cable change today covers decade-level bandwidth growth. Price difference is often <€0.25/m [Amazon list, 2023].
Do I need to ground shielded RJ-45 cables?
Yes. Bond the drain wire to an earth point at patch panel and switch. Leaving it floating negates the shield benefit and may introduce ground loops [Siemon, 2019].
Can a cheap crimper really slow my network?
Yes. Mis-seated contacts raise insertion loss and packet retries. “Better throw that pincer into the trash” [Elektroda, Anonymous, post #17552568]
How do I test if electrical cables nearby cause interference?
Pull the network cable out of the strip and retest on the floor; if speed climbs, the route is noisy [Elektroda, leonov, post #17545907]
Quick 3-step check for a healthy Gigabit link
- Confirm NIC reports 1000 Mb/s full-duplex.
- Copy a 4 GB file between two PCs; expect ≥110 MB/s.
- Record errors in switch port stats; counters should remain near zero.
Could antivirus software throttle Speedtest results?
Yes. Some security suites scan traffic and cap throughput until tuned. One user regained full 300 Mb/s after vendor-guided changes [Elektroda, MANTA20E, post #17552724]
Edge case: new cable yet port still negotiates 100 Mb/s—why?
Damaged router jack, auto-MDIX mismatch, or badly bent cable (>4× diameter) can force down-shift. Swap ports and re-test [Elektroda, Anonymous, post #17552207]
What bend radius can Cat 6a tolerate in tight baseboards?
Keep bends ≥25 mm (≈4× 6a diameter). Tighter curves raise crosstalk and may fail certification [Belden, 2022].
