A Layer 2 switch forwards frames based on MAC addresses within a single network, while a router forwards packets based on IP addresses between different networks.

Core distinction

  • A Layer 2 switch operates at the Data Link layer (Layer 2) of the OSI model and uses MAC address tables to decide which port to send frames to inside the same LAN or VLAN.
  • A router operates at the Network layer (Layer 3) and uses IP routing tables to move packets between different IP networks or subnets, making wide‑area communication possible.

How each device “thinks”

  • Layer 2 switch logic: “Which port is associated with this destination MAC address on my local segment?” It learns MAC–port mappings by watching traffic and then forwards unicast frames only to the correct port.
  • Router logic: “What is the best next hop for this destination IP network?” It consults a routing table (static routes or dynamic protocols like OSPF/BGP) and decrements the IP TTL as it forwards between networks.

Scope of traffic

  • Layer 2 switches keep traffic inside a broadcast domain; they forward unicast frames selectively, but broadcasts (like ARP) still reach all devices in that VLAN.
  • Routers separate broadcast domains; a broadcast in one LAN does not cross the router into another subnet, which is essential for scaling and controlling traffic.

Addressing and tables

  • Layer 2 switch main table: MAC address table mapping MAC addresses to physical switch ports; it does not need to understand IP logical addressing to do basic forwarding.
  • Router main table: IP routing table mapping IP networks to next hops or interfaces; it inspects IP headers and often also supports ACLs, NAT, QoS, and VPN features.

Simple analogy

  • A Layer 2 switch is like an apartment building lobby directory: it sends visitors to the correct door once it knows which person (MAC) lives behind which door (port) in that one building.
  • A router is like the city road system and signposts: it decides which road to take to reach a different neighborhood or city (IP network), then hands off to other routers along the path.

TL;DR: The fundamental distinction is local, MAC‑based frame switching within one Layer 2 domain versus IP‑based routing between separate Layer 3 networks. Layer 2 = same network segment; router = between networks.