Network Hardware
Part of Networking
The physical devices that build and interconnect networks.
Why This Matters
A network is not just software and protocols — it is physical hardware. Cables, connectors, network interface cards, switches, routers, and access points are the tangible components that must be selected, installed, configured, and maintained. Understanding what each type of hardware does, what distinguishes quality hardware from inferior equipment, and how to evaluate and repurpose salvaged hardware is essential for anyone building or maintaining a network.
In a reconstruction context, hardware knowledge is particularly important because you may be working with salvaged or repurposed equipment rather than purchasing new hardware. Knowing what you have, whether it is functional, and how to configure it determines whether your network works reliably or intermittently fails in frustrating ways.
This article covers the main categories of network hardware, focusing on practical knowledge for identification, evaluation, and use.
Network Interface Cards
A Network Interface Card (NIC) is the hardware component inside a computer that connects it to the network. Every NIC has a MAC address burned into its firmware — a unique 48-bit identifier used for Ethernet addressing. Most modern computers have NICs built into the motherboard (integrated NICs) rather than as separate expansion cards.
Identifying NICs: In Windows, Device Manager lists network adapters. In Linux, ip link or ifconfig lists network interfaces. The interface name (eth0, enp3s0, wlan0) indicates the type — eth or enp for wired Ethernet, wlan for wireless.
Evaluating NICs: All modern NICs support at least 1 Gbps speeds. For high-performance applications, server NICs support 10 Gbps or 25 Gbps. The driver support matters as much as the hardware — a NIC with good Linux driver support is more valuable than a faster NIC that requires proprietary drivers. Intel and Realtek NICs have excellent Linux driver support; some Broadcom and Marvell models have good support while others are problematic.
For network capture and analysis, a NIC that supports promiscuous mode (receiving all frames on the segment, not just those addressed to it) is needed. Most NICs support this mode; some wireless adapters do not. Monitor mode (capturing raw 802.11 frames in wireless) is supported by fewer devices and requires specific driver support.
Switches
A switch is the central device in a modern Ethernet network. It maintains a MAC address table mapping each known MAC address to the port where it was last seen. When a frame arrives, the switch looks up the destination MAC address and forwards the frame only to the appropriate port — unlike a hub, which floods all ports.
Managed vs. unmanaged switches: Unmanaged switches work out of the box with no configuration and provide basic switching. Managed switches add configuration interfaces (web GUI, command line, SNMP) that allow VLAN configuration, port mirroring, quality of service, spanning tree configuration, and detailed port statistics. For any network larger than a small office, managed switches are preferable because they provide visibility and control.
Switch capacity: The key specification is whether the switch is line-rate (can forward traffic at full port speed simultaneously on all ports) or oversubscribed (the backplane capacity is less than the sum of all port capacities). Line-rate switches are more expensive but necessary for high-throughput applications. Most unmanaged desktop switches are oversubscribed; most rack-mount managed switches are line-rate.
Evaluating salvaged switches: Power on the switch and check that all link LEDs are functional. Connect a device to each port and verify link LED and connectivity. Look for evidence of overheating damage (yellowing or warping of the chassis, burn marks on components). Test throughput with a large file transfer — a switch with failing memory may forward small packets correctly but fail on large transfers.
Routers
A router connects different networks and forwards packets between them based on IP addresses. Where a switch makes forwarding decisions using MAC addresses within a single network, a router makes forwarding decisions using IP addresses across network boundaries.
Every router has at least two network interfaces — one on each connected network. Packets arriving on one interface are forwarded to the appropriate other interface based on the destination IP address and the router’s routing table. The routing table maps destination network prefixes to the next-hop interface or router address.
Consumer routers (home routers) combine multiple functions: router, switch (multiple LAN ports), wireless access point, DHCP server, and often a firewall. This combination is convenient but conflates separate functions that should ideally be separated for flexibility.
Enterprise routers handle routing only, leaving switching to dedicated switches and wireless to dedicated access points. This separation allows each function to be optimized independently and scales to much larger networks.
Repurposing computers as routers: Any computer with two or more network interfaces can function as a router. Linux-based router distributions (OpenWrt, pfSense, VyOS) provide router functionality on commodity hardware. The minimum hardware requirement is modest — a router for a small organization can run on hardware from 2005 or later.
Wireless Access Points
A wireless access point (WAP) provides wireless network connectivity by bridging between the wireless medium and a wired Ethernet network. Clients connect wirelessly to the WAP, and the WAP passes their traffic to and from the wired network.
802.11 standards: 802.11b/g/n operate in the 2.4 GHz band; 802.11a/ac/ax operate in the 5 GHz band. The 2.4 GHz band provides longer range and better obstacle penetration but is more congested. The 5 GHz band provides faster speeds but shorter range. Dual-band access points operate in both bands simultaneously.
Placement and coverage: A single WAP covers a roughly circular area determined by transmit power and obstacles. Walls, floors, and metal objects reduce range significantly. For full coverage of a building, multiple WAPs are needed, with carefully chosen placement and channel assignments to avoid interference between them. WAPs on the same channel interfere with each other; overlapping WAPs should use non-overlapping channels (1, 6, and 11 in the 2.4 GHz band).
Security configuration: Always configure WPA2 (or WPA3 if available) encryption for wireless networks. WEP encryption is broken and should never be used. A strong passphrase prevents unauthorized access. Separate guest networks (using VLANs) isolate untrusted devices from internal network resources.
Cables and Patch Panels
Structured cabling — permanent cable runs in walls and ceilings, terminated at wall plates and patch panels — forms the physical infrastructure of most building networks. Cables are run from each location where a network connection is needed to a central distribution point (wiring closet or telecommunications room).
Patch panels provide a way to terminate multiple cables in one place and connect them to switches with short patch cables. Changing which device connects to which switch port requires only changing a patch cable in the wiring closet rather than re-running cables.
Cable categories: Cat5e (Category 5 enhanced) supports 1 Gbps up to 100 meters. Cat6 supports 1 Gbps with more headroom and 10 Gbps up to 55 meters. Cat6a supports 10 Gbps up to 100 meters. For new installations, Cat6 or Cat6a is the practical choice — the incremental cost over Cat5e is small and the additional headroom prevents the need to re-cable for future upgrades.
Cable testing: A cable tester verifies that each of the eight conductors is correctly connected from one end to the other. It checks for opens (broken conductors), shorts (conductors touching each other), and miswires (conductors crossed to wrong pins). Cable testers range from simple continuity testers (a few dollars) to sophisticated instruments that measure propagation delay, attenuation, and crosstalk. For basic verification of cable installations, a simple continuity tester is sufficient.