How to Run Ethernet Cable Through Walls, Attics and Crawl Spaces

Pulling Ethernet through finished walls is 20% cable work and 80% not making holes you'll regret. This is the field guide: route planning, the code rules that matter, the tools that make fishing cable almost fun, and the spots where cheap cable costs you a wall repair.

Plan the routes before touching a drill

Map every drop on paper first — which rooms, how many jacks each (run two per location; the second costs almost nothing while the wall is open), and where everything converges. Vertical paths are your friends: interior walls are usually hollow top to bottom, and closets that stack floor-over-floor are free elevator shafts for cable. Our home network plan covers the network design half; this article is the physical half.

Jacket ratings are fire code, not marketing

Inside walls between floors, code cares what your cable jacket does in a fire. CMR (riser) rated cable is the standard for vertical runs inside residential walls; CMP (plenum) is required in air-handling spaces like some drop ceilings; ordinary CM is for patch cords in the open. Inspectors and insurers both read these letters. The full decoder is in our fire ratings guide, and our bulk boxes list the rating on every product.

The toolkit: fish tape, glow rods, and a strong magnet

A fish tape pushes/pulls through enclosed cavities; fiberglass glow rods are better for attics and insulation because they stay stiff over distance; a magnetic pull kit (magnet on a chain dropped in the wall, caught with a handheld magnet) feels like cheating in the best way. Add a long flexible drill bit for top plates, painter's tape to label everything, and pull string — always pull an extra string with every cable so the next run needs no fishing at all.

Drilling without drama

Come in through the top plate from the attic or the bottom plate from the basement/crawl space — never horizontally through studs unless you must (holes in studs have depth and edge-distance rules, and that's where wall-interior surprises live: plumbing, romex, gas lines). Drill the plate directly above/below your wall opening, drop the cable, and catch it at the box cutout. Locate the cavity by measuring from a shared reference (a window edge, a vent) in both rooms, and confirm with a small pilot hole inside the future wall-plate cutout, where mistakes are free.

Finish like a pro: boxes and keystones

Use low-voltage old-work brackets (open-back rings that clamp to drywall — no electrical box needed for data), and terminate every in-wall run into a keystone jack, not a bare plug. It strain-relieves the solid-core cable and gives you a wall plate that looks intentional. The termination steps are in our keystone and RJ45 guide. Keep data a few inches from parallel electrical runs where practical, and cross power lines at right angles.

Attics, crawl spaces, garages and gnaw hazards

Exposed horizontal runs in attics and crawl spaces are where cable gets stepped on, cooked and chewed. Route along joists, staple with rounded cable staples (never crush the jacket), keep clear of hot flues and recessed light housings — and in spaces where mice have opinions, spend the extra on armored Cat6A; our anti-rodent guide explains when the spiral steel earns its keep.

Do the planning, respect the jacket ratings, pull a spare string, and test every drop before closing up — future-you, staring at a finished wall, will be grateful. Cable's here: Cat6, Cat6A, and 1000 ft bulk.