I recently enlisted in the Army National Guard as 25N and spent a considerable amount of time researching exactly what 25N does. Here is the best information that I could find, hopefully it helps others out who are looking at this mos.
Basic Description from Goarmy.com:
With communication being such an integral and critical part of the Army, Nodal Network Systems Operator-Maintainers are responsible for making sure that the lines of communication are always up and running. They install, operate, maintain and repair strategic and tactical nodal systems.
Some of your duties as a Nodal Network Systems Operator-Maintainer may include:
Install, initialize, operate and perform field level maintenance on electronic nodal assemblages, combat net radios, and ancillary communications equipment
Use computers and software tools to perform system/network operations
Interpret system and equipment error codes to correct system faults
Install, operate, maintain, perform maintenance and unit level maintenance on all internal communications systems and COMSEC devices
Execute the installation, operation, PMCS and field level maintenance on numerous network management systems
GoArmy.com/25N
The equipment that 25Ns use:
http://www.globalsecurity.org/space/systems/jnn.htm
Other helpful links:
https://forums.goarmy.com/thread/205817
https://www.cool.army.mil/enlisted/25n.htm
http://community.armystudyguide.com/groupee/forums/a/tpc/f/4291043041/m/1951067061
http://militaryyearbookproject.com/cmf-25-communication-and-information-systems-operation/25n-nodal-network-systems-operator-maintainer