VLAN

A router or AP system often exposes several Wi-Fi names: office, guest, IoT, kids. They all appear as SSID (Service Set Identifier) entries, but behind them they may be the same LAN or completely isolated networks.

Whether multiple Wi-Fi names are multiple networks cannot be decided from the names. The key is where each SSID is bridged, which VLAN (Virtual LAN) it maps to, who assigns addresses, and whether isolation policy blocks Layer-2 discovery or Layer-3 access.

Two hosts plugged into the same switch do not automatically belong to the same local network. In the field, a problem may look like “the IP is wrong” or “the firewall is blocking it”, but it may have died earlier at the Layer-2 boundary: ARP broadcasts only spread on part of the ports, DHCP Discover never leaves the segment, and packet capture shows traffic on the link while the target device still acts as if it were on another network.