The lowest layer of the internet protocol suite is the link layer, which is the realm of adjacent hosts on a LAN segment. Link layer communication protocols don't leave the network via routers, so it's important to be aware of them and their weaknesses when you are attacking LANs. When you join a LAN, even a restricted one outside of the protected network, you're sharing that space with anything else on that segment: the captive portal host itself, other clients waiting to be authenticated, and in some cases, even with authenticated clients.
The unqualified term LAN, doesn't necessarily mean that all members of the LAN are in the same broadcast domain, also called a layer-2 segment. For our purposes here, ...
