How to Terminate Ethernet Cable

Two Termination Methods

Ethernet cable is terminated in one of two ways depending on its end use. Keystone jack punch-down is used for in-wall structured cabling — the solid conductor cable is pushed into the IDC (Insulation Displacement Connector) slots of a keystone jack using a punch-down tool, and the jack snaps into a wall plate or patch panel. RJ45 crimping is used for patch cords — stranded conductor cable is inserted into an RJ45 plug and crimped with a dedicated tool. These two methods use different cable types (solid vs stranded) and different tools, and are not interchangeable.

Keystone Jack Punch-Down

This is the correct method for terminating the ends of in-wall runs at a wall jack or patch panel.

1. Strip the jacket: Remove 1–1.5 inches (25–38 mm) of outer jacket using a cable stripper or careful knife cut. Do not nick the individual conductors.
2. Separate pairs, do not untwist: Fan the four pairs out to identify colors, but keep each pair twisted until the moment you seat the conductor into the jack slot. Untwisting more than 13 mm (half an inch) past the jack body degrades crosstalk performance — this is the most common mistake in DIY terminations.
3. Seat wires into the IDC slots: Most keystone jacks are labeled with both T568A and T568B color codes. Press each conductor fully into the correct slot following your chosen standard. The conductor should seat in the slot with the insulation held by the IDC contacts.
4. Punch down: Use a punch-down tool (110-type blade for most keystone jacks) with firm, single-strike pressure per conductor. The tool simultaneously seats the wire and trims the excess. Use the "cut" side of the blade facing outward. A weak or partial punch-down creates an unreliable IDC contact.
5. Close the jack cap: Snap the strain relief cap over the terminated wires. This protects the IDC connections and provides bend radius control for the cable entering the jack.

RJ45 Crimping

This is the correct method for making patch cords from stranded conductor cable.

1. Strip the jacket: Remove about 1.25 inches (32 mm) of jacket. For pass-through plugs (EZ-RJ45 style), you can strip more and trim flush after crimping.
2. Untwist and straighten: Untwist all pairs and arrange the 8 conductors in T568B (or T568A) color order, holding them flat and parallel.
3. Trim to length: Cut the conductors to equal length — approximately 0.5 inches (13 mm) protruding beyond the jacket. The jacket itself must enter the plug body far enough for the strain relief to grip it (the plug's crimp tab must clamp the jacket, not just the conductors).
4. Insert into plug: Slide the conductors into the RJ45 plug with the clip facing down, maintaining color order. Each conductor should reach the front of the plug and be visible through the plug tip.
5. Crimp: Insert the plug into the crimping tool and squeeze firmly in one motion. The crimp drives the IDC contacts through each conductor's insulation and locks the strain relief on the jacket.
6. Test: Use a wire map tester to verify all 8 pins on both ends before using the cable.

Critical Rules for Both Methods

• Maintain pair twist to within 13 mm of the termination point — untwisting farther introduces crosstalk that can prevent gigabit operation.
• Use solid conductor cable for punch-down; stranded for RJ45 crimping. Using stranded wire in 110-type IDC blocks produces unreliable contacts.
• Keep the cable jacket intact into the connector body — strain relief must grip the jacket, not the individual conductors.
• Label both ends of every run before moving to the next cable.

Frequently Asked Questions

My gigabit link keeps falling back to 100 Mbps after I re-terminated — what did I do wrong?

The most common cause is excessive pair untwisting during termination. Gigabit Ethernet (1000BASE-T) uses all four pairs and is sensitive to near-end crosstalk (NEXT), which increases dramatically when pairs are untwisted beyond the 13 mm limit. Re-terminate the jack or plug, keeping each pair twisted until the wire enters its IDC slot or the RJ45 plug channel. The second common cause is a split pair — wires from two different pairs used together (e.g., white/orange on pin 1 and white/green on pin 2, instead of white/orange and orange). Visually verify the color order against the T568A or T568B diagram before punching down.

Can I terminate Cat6A cable with standard Cat6 keystone jacks?

No, not for a compliant Cat6A installation. Cat6A requires Cat6A-rated jacks and patch panels designed for the thicker Cat6A conductor gauge and the tighter crosstalk specifications at 500 MHz. A standard Cat6 jack physically accepts Cat6A conductors but cannot meet Cat6A channel performance — the jack becomes the weakest link and limits the channel to Cat6 performance. If you are pulling Cat6A cable, buy Cat6A jacks, patch panels, and patch cords. The incremental cost is modest compared to the labor cost of re-doing the terminations later.

Do I need to use the punch-down tool that came with the keystone jack?

No — any 110-type punch-down tool works with standard keystone jacks. What matters is that the blade is 110-type (the near-universal standard for structured cabling jacks) and the tool provides enough impact force to fully seat the conductor. A good punch-down tool has an adjustable impact setting — use medium or high for solid conductors in keystone jacks. Cheap screwdriver-style punch-down tools without a spring mechanism often produce weak, unreliable contacts. If a link fails a wire map test after punch-down, re-punch the suspect conductors with firm, clean strikes before assuming the jack or cable is defective.