Ethernet Cable Jacket Ratings: The Route Decides
Quick answer / TL;DR: Short answer: CM is general-purpose indoor; CMR adds riser capability for vertical shafts; CMP adds plenum rating for air-handling spaces; outdoor ratings add UV and moisture resistance. The route decides the jacket, the category decides the performance – specify both, e.g. 'Cat6 F/UTP, CMP, 305 m box'.
The jacket rating is the cable's permission slip: it states where the cable may run. The same copper inside four different jackets serves a desk, a riser shaft, an air-handling ceiling, and a buried conduit – and the wrong jacket fails inspection regardless of the category.
This is the ratings guide: the common codes, the routes they unlock, and the order language.
The Common Ratings
| The rating | The route it permits | The note |
|---|---|---|
| CM | General indoor horizontal runs | The baseline |
| CMR | Riser shafts between floors | Vertical runs in buildings |
| CMP | Plenum – air-handling ceilings | The most restrictive indoor rating |
| Outdoor | Exterior, wet, buried | UV and moisture resistance |
The ratings stack by route: a plenum cable can serve a general run, but a general cable cannot serve a plenum.
How the Route Decides
- Where does the cable physically run? The route's fire and moisture environment sets the rating
- Ceiling voids that return air are plenum spaces – CMP applies
- Vertical shafts between floors are risers – CMR applies
- Exterior and buried runs need outdoor constructions
The route question comes before the category question: the jacket is a building-code matter, the category a performance one.
The Order Language
| The need | The order line |
|---|---|
| Office horizontal | Cat6 U/UTP, CM, 305 m box |
| Riser backbone | Cat6 F/UTP, CMR |
| Plenum ceiling | Cat6a F/UTP, CMP |
| Exterior conduit | Cat6 F/UTP, outdoor rated |
Standards and Verification
| The reference | The relevance |
|---|---|
| UL 444 / NEC articles | The jacket ratings and their permitted uses |
| TIA-568.2-D | Cabling practice by route |
| Jacket print | The rating marking that proves the claim |
Per-market code editions are not provided in the knowledge base. The ratings are standard; confirm the route's requirement with the local authority.
Real-World Applications
The plenum ceiling
A ceiling void returning air to the HVAC: CMP cable specified – the inspection passed on the print, not on an argument.
The riser shaft
A backbone climbing four floors: CMR jacket – the vertical route's requirement met at the cable order.
The mixed order
A project ordering one cable for three routes: the ratings separated – three order lines, three jackets, one category.
Related reading: The riser-versus-exterior question? Read CMR versus outdoor — blogs/news/cmr-outdoor-rating
Related reading: The outdoor Cat6 variant? Read is Cat6 outdoor rated — blogs/news/cat6-outdoor-rated
Frequently Asked Questions
What do CM, CMR and CMP mean?
Jacket ratings for indoor routes: CM general, CMR riser (vertical shafts), CMP plenum (air-handling spaces).
Can I use CM cable in a plenum ceiling?
No – plenum spaces require CMP. The jacket rating is a code requirement, not a preference.
What rating is outdoor cable?
Outdoor constructions add UV and moisture resistance; direct-burial types add mechanical protection. They are separate from the indoor ratings.
Does the jacket affect performance?
Not the category's bandwidth – the jacket governs where the cable may run. Specify category and jacket together.
Sourcing FTP (F/UTP) Cat6 for a project, a store, or a shielded system? Contact our B2B sales team for shield construction data, category reports, and volume terms – FOB and CIF options available. Request a quote or sample.