Network Access
Network access focuses on switching, VLANs, and wireless connectivity within the LAN. You will learn how switches build MAC address tables, how VLANs segment traffic, and how trunks carry multiple VLANs using 802.1Q tagging. The domain also covers loop prevention with STP, link bundling, and WLAN fundamentals.
Switching Concepts
A switch learns source MAC addresses from incoming frames and builds a MAC address table to forward frames only out the correct port. Unknown-unicast, broadcast, and multicast frames are flooded to all ports in the VLAN. Switches make forwarding decisions in hardware for low latency. Each switch port is its own collision domain, while a VLAN defines a broadcast domain.
VLANs and Trunking
VLANs logically segment a switch into separate broadcast domains, improving security and reducing broadcast scope. Access ports carry a single VLAN toward end devices, while trunk ports carry many VLANs between switches. IEEE 802.1Q inserts a 4-byte tag identifying the VLAN, leaving the native VLAN untagged. Consistent VLAN and native VLAN configuration on both trunk ends is essential.
Spanning Tree Protocol
STP prevents Layer 2 loops by electing a root bridge and blocking redundant paths until needed. The switch with the lowest bridge ID (priority plus MAC) becomes root, and other switches choose a root port with the lowest path cost. Rapid PVST+ speeds convergence over classic STP. PortFast and BPDU Guard protect edge ports and stabilize the topology.
EtherChannel
EtherChannel bundles multiple physical links into one logical link to increase bandwidth and add redundancy without STP blocking the extras. LACP is the IEEE 802.3ad standard for dynamic negotiation, while PAgP is Cisco-proprietary, and both can also be configured statically. All bundled ports must share matching speed, duplex, and VLAN settings. Traffic is load-balanced across the members.
Wireless LAN Fundamentals
Wireless LANs use access points to bridge Wi-Fi clients onto the wired network over shared radio frequencies in the 2.4 GHz and 5 GHz bands. Autonomous APs operate independently, while lightweight APs rely on a Wireless LAN Controller in a split-MAC design using CAPWAP. The SSID names the wireless network, and non-overlapping channels reduce interference. Proper RF planning improves coverage and throughput.