Network Hardware: Routers, Switches, Access Points, Patch Panels, Firewalls, PoE, Modems, ONTs, and NICs
Unit 2: Networking Fundamentals. Lesson 8 of 41 in APlus Academy Core 1.
Walk into a wiring closet and you should be able to name every box and say what it does. Core 1 asks exactly that, plus which device to add for a given need.
Routers
A router connects networks and forwards packets by IP address. In a home or small office the "router" is really several devices in one box: a router, a switch with four ports, a wireless access point, a DHCP server, a NAT gateway that shares one public address, and a basic firewall. In an enterprise these are separate.
Switches
A switch connects the devices of one network and forwards frames by MAC address, port by port. An unmanaged switch has no configuration: plug in and it works. A managed switch has an administrative interface for VLANs, port speed and duplex settings, PoE control, port mirroring, link aggregation, and monitoring through SNMP. If the question mentions VLANs or configuring a port, it needs a managed switch.
Access points
An access point (AP) bridges Wi-Fi clients onto the wired network. It has an SSID, a channel, a security mode, and, in a business, a controller that manages dozens of APs together. A standalone AP is not a router; it does not hand out addresses or do NAT.
Patch panels
Building cable runs from wall jacks end in a patch panel in the closet, punched down onto a 110 block on the back. Short patch cables then connect each panel port to a switch port. The panel protects the permanent cable from wear and makes moves a matter of swapping a patch cable. Labeling is everything.
Firewalls
A firewall allows or blocks traffic by address, port, and rule. A network firewall sits between the internet and the LAN, is usually stateful (it tracks connections so replies are allowed automatically), and may add content filtering and intrusion prevention. A software firewall runs on each host.
Power over Ethernet
PoE sends DC power over the data cable so access points, IP phones, and cameras need no outlet. A PoE switch supplies it from its ports; a PoE injector adds it to a single run from a non-PoE switch. PoE standards: 802.3af delivers 15.4 W per port, 802.3at (PoE+) 30 W, and 802.3bt (PoE++) 60 W (Type 3) or 100 W (Type 4). A device that reboots or will not power up on a long run may be exceeding the budget.
Modems and terminals
- Cable modem: internet over the cable TV coax using DOCSIS; F-type connector; bandwidth shared with the neighborhood.
- DSL modem: internet over the phone line through an RJ11 jack; speed falls with distance from the exchange.
- ONT (optical network terminal): converts the fiber coming into the building to an Ethernet port for the router.
Network interface cards
Every device has a NIC, wired or wireless, with its own MAC address. Desktops can add a PCIe NIC for a faster port or a wireless card; a USB NIC rescues a laptop with a dead port.
Hubs
A hub repeated every frame to every port, causing collisions. It is obsolete; if you find one, replace it with a switch.
Network Hardware: Routers, Switches, Access Points, Patch Panels, Firewalls, PoE, Modems, ONTs, and NICs, explained slowly
The closet as a city
Think of a building network as a city. The router is the highway on-ramp: the only way in and out. The switches are the city streets connecting every house. The access points are bus stops where wireless riders get on. The patch panel is the street directory that maps every house to its cable. The firewall is the checkpoint at the on-ramp. PoE is the power line strung along the streets so the bus stops and cameras need no separate outlet. The modem or ONT is the bridge from the city to the outside world.
Devices compared
device forwards by connects configure? one-line memory hook router IP address networks to networks yes the gateway; NAT; between networks switch, unmanaged MAC address devices on one network no plug and play switch, managed MAC address same, plus VLANs yes (web, CLI, SNMP) VLANs, port settings, PoE control, mirroring access point - Wi-Fi clients to wired SSID, channel, security a bridge, not a router patch panel - wall runs to the closet punch down and label permanent cable stays put firewall rules inside to outside yes allows or blocks by address and port PoE injector - one run no power for a single AP or camera PoE switch MAC address many runs with power yes power budget per port and total cable modem - coax to Ethernet provider DOCSIS, F-type connector DSL modem - phone line to Ethernet provider RJ11, distance-limited ONT - fiber to Ethernet provider the fiber box on the wall NIC - a device to the network driver MAC address lives here hub nothing (repeats) - - obsolete; collisions
The SOHO router is five devices
The box the ISP hands out contains a router (WAN to LAN), a four-port switch, a wireless access point, a DHCP server, a NAT gateway, and a basic firewall. When a question says "the router" in a home context, any of those functions may be the subject. In a business the pieces are separate boxes: a firewall at the edge, a router (or the firewall routing), core and access switches, a wireless controller, and many access points.
Managed versus unmanaged, a worked choice
A dental office needs phones on their own voice VLAN, a guest network for the waiting room, PoE for the phones and two cameras, and the ability to see which port is flapping. Every item on that list is a managed switch feature: VLANs, PoE, and per-port monitoring. An unmanaged switch does none of it. Conversely, a home user adding three ports behind a TV needs an unmanaged switch; there is nothing to configure and nothing to break.
PoE budget math
standard name power at the port typical loads 802.3af PoE 15.4 W phones, small APs, basic cameras 802.3at PoE+ 30 W Wi-Fi 6 APs, PTZ cameras 802.3bt PoE++ 60 W (Type 3), 100 W (Type 4) video phones, large APs, small switches, displays
A 24-port PoE switch might have a 190 W total budget. Twelve PoE+ access points at 30 W would want 360 W, so half of them will not power up, or the switch will drop ports as the budget runs out. A camera that reboots at night when its heater turns on is a budget problem. A PoE injector solves the one-run case: the AP in the far corner where the closet switch has no PoE.
Modems and the ONT
The modem or ONT belongs to the connection type. Coax comes from the street into a cable modem; the phone line goes into a DSL modem; fiber ends at an ONT, a small box that turns light into an Ethernet port. In every case the next device is the router's WAN port. When the internet is down, the modem's lights are the first thing to read: power, downstream, upstream, online.
How the exam asks it
- "Which device connects a fiber line to a customer's Ethernet router?" ONT.
- "A technician needs VLANs and per-port configuration." A managed switch.
- "An access point at the end of a long run needs power but the switch has no PoE." A PoE injector.
- "Which standard provides up to 30 W over Ethernet?" 802.3at, PoE+.
- "Which device terminates the building's cable runs in the closet?" A patch panel.
- "Which device forwards packets between networks?" A router.
What to memorize
- Router by IP between networks; switch by MAC within a network; managed = VLANs and settings.
- Access point bridges Wi-Fi to wired; not a router. Patch panel: punch down, patch cables, labels.
- PoE af 15.4 W, at 30 W, bt 60 or 100 W; injector for one run; switch for many; watch the budget.
- Cable modem DOCSIS and F-type; DSL RJ11; ONT for fiber. Hub is obsolete.