Campus Access Networking Fundamentals
What this domain covers
Campus access networking is about how endpoints reach the network and how traffic moves between them. You must be comfortable with the OSI model layers that matter operationally - Layer 2 (Ethernet, MAC addressing, switching) and Layer 3 (IP addressing, routing, ARP) - and with the idea that a campus is typically a hierarchical design: access layer (edge switches facing users and APs), distribution/core layer (aggregation and routing), and the WAN/edge. Understand broadcast domains, collision domains, and how VLANs segment one from the other. Know the difference between a routed (Layer 3) and switched (Layer 2) boundary, and why a default gateway lives on a router or Layer 3 switch.
Traps to watch
Questions love to blur "collision domain" and "broadcast domain." A switch port is its own collision domain; a VLAN is a broadcast domain. Another trap: confusing MAC addresses (flat, 48-bit, locally significant) with IP addresses (logical, routable). Also expect questions on ARP (maps IP to MAC within a subnet) versus routing (moves packets between subnets).
Worked example / rule of thumb
Rule of thumb: one VLAN = one subnet = one broadcast domain. If a host at 10.1.10.5/24 talks to 10.1.20.5/24, it does not ARP for the destination - it ARPs for its default gateway and sends the frame there. If both are in 10.1.10.0/24, it ARPs directly for the destination's MAC.