Command Network Module

The External Command Network Module or CNM, is an external helmet attachment utilized by the United Nations Space Command.

Usage
Two different models are known, one designed for the Military Police helmet, and an Up-Armored variant for the ODST helmet. The former is standard issue to Special Force unit commanders and Beta-5 Security units patrolling the Inner Colonies, while the latter seems to be exclusively used by the ODSTs, most often squad commanders. The two devices differ in appearance as well as their pricing.

Halo Reach
The CNM is available as a helmet accessory in Halo: Reach. The device for the MP variant is priced at 5,000 cR, while the ODST variant is priced at 1,000 cR.

Trivia
During the Halo: Reach Multiplayer Beta, the Mark V[B] helmet had a CNM upgrade available. The device cost 2,000 cR, but was cut from the final game. In the Beta, it was known as the Hardened External Sensor Array-External.

List of appearances

 * Halo 3: ODST
 * Halo: Reach
 * Halo: Fireteam Raven
 * Halo Mythos: A Guide to the Story of Halo