Physical infrastructure is the cable, connectors, switches and radio or fibre links that carry a network, and in a rebuilt settlement almost all of it is salvaged, so the first job is to survey, test and label what exists. Twisted-pair copper serves runs up to 100 m, fibre or a directional radio link covers the gaps between buildings, and the cable outlasts the electronics, so install it carefully and write down where every run goes. A village cannot newly manufacture any of this equipment, which makes every working part a spare to protect.
Part of Networking
The cables, connectors and active boxes that make up the physical network, and how to survey, choose and document them.
The Cable Outlasts The Electronics, So It Is The Part To Get Right
Network Types makes the economic point: upgrading a local network from 100 Mbps to 1 Gbps needs only new switches and network cards, not new cable. The same holds in reverse for a salvaged network. Switches and cards will fail and be replaced from whatever is found, while the cable in the walls stays. Twisted Pair Wiring adds that runs through walls and ceilings are hard to reach after installation, so the work done once at installation is the work that is not redone.
Use the medium that fits each distance:
| Distance | Medium | Article |
|---|---|---|
| Within a room or building, up to 100 m | Twisted-pair copper | Twisted Pair Cabling |
| Between buildings | Fibre, or radio | Fiber Optics, Wireless Bridges |
| Between settlements | Directional radio | Wireless Bridges |
| Joining the cables together | Switches | Network Switches |
The existing articles give different reach for radio links: Network Types says 10-50 km and the carrier Internet Infrastructure says up to 30 km with clear line of sight. Treat both as ceilings that need a clear path and tall masts, not as promises.
What You Need
- A survey of what exists — which buildings already have cable in the walls, which have patch panels, which have switches and cards
- A tester — Cable Testing shows how to do it even with a battery and a meter
- Labels — Physical Connections says to label every cable at both ends at installation
- Paper — a hand-drawn diagram of every run and its length
Method: Survey, Test, Choose, Label
Step 1: Walk the buildings and list what is installed Note cable type, whether connectors are fitted, and where each run ends. Check Network Hardware for how to judge salvaged cards and switches.
Step 2: Test everything before relying on it A cable that looks fine can have a broken conductor or a split pair. Test each run and discard or re-terminate the failures.
Step 3: Lay out a star Star Topology gives the rule: no run longer than 90 m, leaving 10 m for patch cables at the two ends within the 100 m limit, and 20-30% spare switch ports for growth.
Step 4: Keep cable away from other wiring The sources in this section disagree on separation from mains wiring: Physical Connections says at least 100 mm, Twisted Pair Wiring says 150 mm, and the carrier says 15 cm. Use the larger figure, and cross mains cable at 90 degrees rather than running alongside it.
Step 5: Label and draw Every cable and every switch port gets a label, and the diagram goes on paper in the equipment room, since the machine that holds the digital copy may be the one that is down.
Worked Example: Sizing A Wiring Closet
A school has 40 places that need a network socket. Star Topology asks for 20-30% spare ports. At 20% spare: 40 x 1.2 = 48 ports. At 30% spare: 40 x 1.3 = 52 ports. Two 24-port switches give exactly 48, which meets the lower end. Meeting the upper end needs 52 ports, so a third switch or a larger one. Each link between switches also uses a port on both of them, so count uplinks as well.
Common Mistakes
- Reusing cable without testing it — salvaged runs can have broken conductors or damaged insulation that only a test shows
- No documentation — the carrier lists this first among common mistakes: nobody can troubleshoot or rebuild when the one person who remembers the layout is unavailable
- Putting every machine on one switch with no spare ports — the first new machine then forces a rewire
Safety
Treat unknown cable and wiring in salvaged buildings as live
Network cable is often pulled out of walls and ceilings that also contain mains wiring, and a building may have been re-energised by a generator, solar array or battery bank. Do not cut or strip any cable until you know what it is, and treat any mains-type wiring as live until you have proved it dead. See Electrical Safety. Work from a stable ladder, never from a stack of loose furniture, and do not enter a damaged building to pull cable.
What’s Next
- Learn next: Twisted Pair Cabling — making and laying the cable that does most of the work
- Combine with: Connectors — the part of the cable that most often fails