Linking Internet Between Buildings

Plenty of situations need internet to cross a gap: rooms in a rear building, an office with a warehouse across a lane, a shop at the front with the owner's house behind. Almost everyone tries the same thing first, moving the router to a window, or adding a repeater, and almost everyone is disappointed.

Exterior walls, open distance, and the second building's walls absorb far more signal than expected. The solution that works is not to broadcast harder but to build a bridge: one dedicated link between the two buildings, then an ordinary network inside each.

Option 1: Ethernet cable

Simplest and most reliable when the distance is no more than about 100 metres.

• Use outdoor-rated cable, whose jacket resists sunlight and water. Indoor cable turns brittle and cracks within a year or two in the sun.
• Bury it in conduit, or run it along a support wire if overhead. Do not let it hang by its own weight.
• Avoid running it close and parallel to power cables over long stretches.
• A cable running outdoors can carry surges from nearby lightning. Network surge protectors at both ends cost little compared with a burnt router.

Option 2: fibre optic

For distances over 100 metres, or places prone to lightning, fibre is the calmest choice. Glass does not conduct electricity, so lightning surges do not travel along it, and it can span kilometres.

You need the fibre cable and, at each end, a media converter (or a switch with a fibre port) to turn it back into ordinary Ethernet. Installation needs special splicing tools, so a technician usually does it, but once in place, there is almost nothing to maintain.

Option 3: point-to-point wireless

When running cable is impossible, across a road, a river, or someone else's land, a pair of point-to-point wireless units is the answer. Both use directional antennas facing each other, concentrating the signal in one direction rather than spreading it everywhere.

• Line of sight is mandatory. The two units must see each other. A small tree today can be an obstruction next year.
• Mount as high as possible on a pole or upper wall, above people and vehicles.
• Align carefully. Most units have a signal-strength indicator to help.
• Choose the 5 GHz band for speed, and make sure the equipment is certified for use in Indonesia.

Over a few hundred metres with a clear line of sight, a mid-range pair can carry tens to hundreds of Mbps reliably.

Once the bridge is in

In the second building, connect the bridge to an access point or a router in access-point mode. Do not make it a second router handing out its own addresses unless you mean to, two router layers stop devices in the two buildings seeing each other and complicate management. How to do this is covered in the guide to setting up two routers on one network.

In short

Under 100 metres and cable is possible: outdoor Ethernet. Further, or lightning-prone: fibre. No cable possible at all: point-to-point wireless with a clear line of sight. Whichever you choose, the bridge only carries the internet across, the second building still needs its own access point.

Frequently asked questions