Network Devices, Cabling, and Topologies
This domain tests the hardware that moves frames and the media that carry bits, plus the shapes networks are built in. Expect matching questions on device-to-layer mapping and on cable category, connector, and distance limits.
Devices by function
- Hub/repeater: Layer 1, one collision domain, half duplex, obsolete.
- Switch: Layer 2, learns MAC addresses, one collision domain per port, floods broadcasts.
- Router: Layer 3, separates broadcast domains, runs routing protocols.
- Firewall: filters on ACLs, connection state, or application; often the Layer 3 boundary.
- Access point: bridges wireless clients onto the wired LAN; a wireless controller centralises many APs.
- Load balancers, proxies, and IDS/IPS distribute or inspect traffic inline or out of band.
Cabling
- UTP Cat5e: 1 Gbps to 100 m. Cat6: 10 Gbps to 55 m, 1 Gbps to 100 m. Cat6a: 10 Gbps to 100 m. The 100 m channel limit includes patch cords at both ends.
- Fiber: multimode for short building runs, single-mode for long haul. Common connectors are LC, SC, and ST.
- Straight-through connects unlike devices (PC to switch); crossover connects like devices (switch to switch). Auto-MDIX makes this mostly moot in practice, but the exam still tests it.
Topologies
Star/hub-and-spoke dominates LANs: one failed link takes down one host only. Full mesh gives maximum redundancy at high cost; partial mesh balances both. Physical topology is the cabling; logical topology is how traffic actually flows.
Worked example
A 70 m run between two access switches must carry 10 Gbps. Cat5e is out because 10GBASE-T needs better cable. Cat6 only guarantees 10 Gbps to 55 m, so specify Cat6a, or multimode fiber with matching SFP+ transceivers at both ends.
Traps
Measuring only the horizontal run and ignoring patch cords. Assuming fiber works without the right transceiver and connector polish. Confusing a physical star with a logical star.