[pumplekin]

The idea of an IX, or IX peering LAN is simple in concept. It is a LAN (a flat, layer2 network), to which multiple ISP's can plug in routers.

Like your home LAN might have 192.168.0.1 = router, 192.168.0.2 = laptop, 192.168.0.3 = phone etc, a peering LAN will have things like 195.66.224.21 = HurricaneElectric, 195.66.224.22 = NTLI, 195.66.224.31 = Akamai, 195.66.224.48 = Arelion etc ...

So instead of all these ISP's that want to exchange traffic with each other having to assign ports and run cables in a full mesh (which quickly would get out of control), everyone connects to the "big switch in the middle" with that peering LAN on it, and they use that.

Back in the day, that might have been an actual single big switch, or a stack of switches. Now IXP infrastructures are much more complex, but the presentation to the end user is usually still a cable (or bundle of cables) that goes into something that looks to them like a "big switch".

There is a LOT more to know about this space (Peering vs Transit, PNI's, L3 internet exchanges, what Google are doing by withdrawing from IXP's), but I wanted to write a comment that didn't turn into an essay.