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Getting FDMA Working on a CPN

As per my last post, I will show here the basic configuration of how to get FDMA working on a Lot 10 CPN. All CECOM documentation only shows how to get a JNN working, but (as CPNs don’t have a GPS to provide timing) we have to do things differently.


  • TFOCA-2 runs from Port 1 on the LOS case to J1 on the STT. In our LOS case, we had to use the spare fiber pair to connect to the CTM-100/C.
  • Serial cable connects from NT2R Serial0/0/0 to the LOS case’s Channel 1 Red.
  • Serial patch from Port 1 NRZ to Channel 1 Black (all on the LOS case).
  • FDMA modem and CTM-100/C installed as labeled in the STT.
  • KIV-7M installed as labeled in the LOS case, COMSEC loaded, and strappings matching the HUB.

CTM-100/C Configurations

The following setup will allow your CTMs to pull timing through your FDMA modem.

Mode Fiber Fiber
Rate <Provided in SAA> <Provided in SAA>
NRZ Mode EIA530A EIA530A
NRZ Clock ——- TXC
Clock Source Fiber Input
Status (when complete) <Rate> nF_ P_ L_ <Rate> Nf_ P_ L_

NT2R Configuration

  • Remove “passive-interface Loopback0” from the OSPF configuration.
  • Add a network statement to include the Hub’s NT2R (e.g. “network area 0”). The IP of the Hub’s NT2R should be visible in your routing table, as it is a directly connected network via Serial0/0/0 (shown in the yellow box below).
#show ip route
NT2R Routing Table


That should be it. If any additional configuration is required, it is Hub-specific and not something we came across. If additional help is required, I can be contacted via this blog (must use a .mil email address).

Published inArmyNetworking