Endpoints and Media Types
This domain covers endpoint devices and the physical media that connect them: copper and fiber cabling, connectors, Ethernet standards, Power over Ethernet, and wireless standards. Questions often ask you to select the right medium for a distance, speed, or power requirement.
Copper cabling
Unshielded twisted pair (UTP) uses RJ45 connectors and T568A or T568B wiring. Cat5e supports 1 Gbps to 100 m. Cat6 supports 1 Gbps to 100 m and 10 Gbps to about 55 m. Cat6a supports 10 Gbps to 100 m. Straight-through cables connect unlike devices; crossover cables connect like devices, though Auto-MDIX usually negotiates automatically. Coaxial cable is common in cable broadband, not typical office LANs.
Fiber cabling
Single-mode fiber has a small core, carries long distances in kilometers, and usually has a yellow jacket. Multimode fiber has a larger core, covers shorter distances, and is typically orange or aqua. Common connectors are LC, SC, and ST. 1000BASE-SX runs on multimode fiber; 1000BASE-LX runs on single-mode fiber. Fiber is immune to electromagnetic interference.
Ethernet and PoE
1000BASE-T uses Cat5e or better to 100 m. 10GBASE-T uses Cat6 or Cat6a. PoE standards: 802.3af delivers about 15.4 W at the power sourcing equipment, 802.3at about 30 W, and 802.3bt up to 60 W or 100 W. PoE powers IP phones, cameras, and access points.
Wireless
802.11n is Wi-Fi 4, 802.11ac is Wi-Fi 5 on 5 GHz, and 802.11ax is Wi-Fi 6/6E. Access points connect wireless clients to the wired LAN. Wireless is a shared, half-duplex medium using CSMA/CA.
Worked example
A 90 m run from a switch to a desk phone needs 1 Gbps and PoE+. Use Cat6 UTP with RJ45 connectors and confirm the switch port supports 802.3at. For a 3 km link between buildings at 1 Gbps, choose single-mode fiber with 1000BASE-LX transceivers; Cat6 cannot span that distance because copper Ethernet is limited to 100 m.
Traps
Cat5 does not guarantee gigabit; Cat5e does. Fiber connectors are not RJ45. Confirm the total PoE budget covers every powered device. Multimode fiber is not for multi-kilometer runs. Wireless uses CSMA/CA, not CSMA/CD.