Quick Answer / Summary: For outdoor runs use cable with a UV-stabilised LLDPE jacket, not standard PVC. Direct burial needs a gel-filled core plus armor or a conduit; aerial spans need a messenger wire or figure-eight construction. Keep every run inside the 100 m channel limit, including the patch cords indoors. Exterior cable is not plenum rated, so it must transition to CMP cable before entering an air-handling space.
Indoor Ethernet cable fails outdoors for reasons that have nothing to do with data rate. Sunlight destroys PVC, water wicks along the sheath, and temperature swings crack a jacket that was rated for a plenum ceiling, not a fence line.
Why Indoor Cable Fails Outside
Standard riser and plenum jackets are formulated for flame and smoke performance, not weather. UV exposure embrittles PVC within a season or two, and the cracks let water into the shield and the pairs.
Water is the more destructive problem. In a flooded or unsealed cable, moisture travels by capillary action and changes the dielectric constant along the run, which shows up as intermittent CRC errors and link drops long before the cable is visibly damaged.
Temperature range
Exterior cables are typically rated from -40 C to 75 C. Indoor PVC may be rated only to 60 C and stiffens badly in cold, which cracks it during installation rather than in service.
UV and ozone
Sunlight degrades the jacket and ozone attacks rubberised compounds. Black LLDPE with carbon black is the standard defence, which is why exterior cable is almost always black.
Constructions and Where Each Belongs
Three constructions cover almost every exterior job: UV-rated unshielded for a sheltered run in conduit, gel-filled for wet locations, and armored for direct burial or rodent exposure.
Choose by the environment the cable will actually live in, not by the cheapest SKU. Replacing a failed buried cable costs several times the price difference.
Gel-filled flooded core
The gel blocks water entry if the jacket is nicked. It makes termination messy and the cable stiff, so leave service loops and clean the gel before crimping.
Armored and direct burial
Corrugated steel tape or an interlocked armor protects against rodents and crush. Direct burial still requires gel filling; armor alone is not a waterproofing system.
Distance, PoE and Grounding
The 100 m channel limit applies outdoors exactly as it does indoors: 90 m of permanent link plus 10 m of patch cords. Cold and moisture do not buy you extra distance, and PoE voltage drop makes long exterior runs worse.
Outdoor cable is also an antenna. Aerial runs between buildings should use shielded cable bonded at one end, plus surge protection at both ends, or you will replace switches after the first storm.
PoE budget
A 30 W PoE device on a 100 m run loses a noticeable fraction of its voltage in the cable. Use 23 AWG or larger conductors for high-power cameras and access points, and check the voltage at the device, not at the switch.
Transition to indoor cable
Where the run enters a building, terminate at a surge protector or a patch panel and switch to CMP or CMR cable. Exterior jackets are not rated for plenum spaces and may violate code.
Exterior Cable Selection
Match construction to installation method.
| Construction | Water | UV | Best installation |
|---|
| UV-rated U/UTP, PVC-free | Poor | Good | Conduit, sheltered wall |
| Gel-filled F/UTP | Good | Good | Wet conduit, underground duct |
| Gel-filled armored | Best | Good | Direct burial |
| Figure-eight with messenger | Good | Good | Aerial span between poles |
| Standard CMR indoor | None | None | Indoors only |
Real Installations
Two outdoor jobs with different failure modes.
Garage or outbuilding link
Bury gel-filled armored Cat6 in conduit below the frost line, leave a drip loop at each entry, and terminate on a surge protector indoors. A 40 m run at 1 Gbps is comfortable; at 10GBASE-T, keep it under 55 m on Cat6 or use Cat6a.
PoE camera on a pole
Use UV-rated cable in conduit up the pole, not zip-tied to the mast where it flexes in wind. Leave a service loop, seal the connector with self-amalgamating tape, and bond the pole to ground separately from the cable shield.
Frequently Asked Questions
Can I run indoor Ethernet cable outside?
It will work for a while and then fail. PVC jackets crack under UV and water enters the core. The replacement cost is higher than buying exterior cable once.
Do I need conduit for direct burial cable?
Not strictly, if the cable is gel-filled and armored. Conduit still helps for future replacement and protects against digging damage.
Does exterior cable change the 100 m limit?
No. The 100 m channel limit applies to the electrical link, regardless of jacket. Beyond that, use fiber or a copper extender.
Is shielded exterior cable better?
Only when it is bonded properly at one end. An ungrounded shield becomes an antenna and can make interference worse.
Can exterior cable enter a plenum ceiling?
No. Transition to CMP-rated cable at the building entry, using a patch panel or surge protector as the demarcation point.
Related resources: Ethernet jacket ratings explained; running Ethernet outdoors; outdoor installation methods
