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NCCER Electronic Systems study materials
NCCER Electronic Systems study resources

NCCER Electronic Systems: Telecommunications and Network Systems

NCCER Electronic Systems · Work through your exam, one topic at a time.

All guide sections

Telecommunications and Network Systems

Telecommunications and Network Systems tests Ethernet, IP addressing, switching, PoE, fiber, and performance testing. Expect questions on subnetting, VLANs, DHCP, DNS, PoE classes, fiber types, connectors, and copper and fiber test results.

Core rules

  • Ethernet and IP operate in layers. A subnet mask separates network and host bits. Usable hosts are 2 to the host bits minus 2 for traditional subnets.
  • VLANs separate broadcast domains and improve security and traffic control. A trunk carries multiple VLANs between switches.
  • PoE standards 802.3af, at, and bt define increasing power classes. Check the switch budget, cable loss, and endpoint class.
  • Multimode fiber uses OM3 or OM4 for shorter building and campus runs; singlemode OS2 uses laser-optimized long-haul transmission. Match transceiver type, connector, and polish.
  • Test copper for wire map, length, insertion loss, and crosstalk. Test fiber for loss, length, and polarity.

Worked example

A network at 192.168.10.0/24 must support 70 devices in one segment. A /26 gives 62 usable hosts, so it is too small. A /25 gives 126 usable hosts, which fits. The /25 mask is 255.255.255.128, with subnets 192.168.10.0 and 192.168.10.128. The technician reserves one subnet for the devices and keeps the other for growth or a separate VLAN.

Traps

Using a /26 for 70 hosts; confusing a VLAN with a subnet; ignoring PoE budget; matching an OM4 patch cord to a singlemode transceiver; and accepting a link that powers up without a certification test.