Mac address table
A MAC address table is a switch data structure that maps learned MAC addresses to the interfaces through which their devices are reachable.
Acing the CCNA Exam: Volume 1 Fundamentals and Protocols
A MAC address table is a switch data structure that maps learned MAC addresses to the ports through which their corresponding devices are reachable.
- How it is used
- Supports Layer 2 frame forwarding within a LAN by mapping destination MAC addresses to switch ports.
- How deep it goes
- Explains learning, aging, forwarding, flooding, Cisco output, and clearing commands, but does not detail memory internals beyond the CAM name.
- Examples
- Uses two-switch PC topologies, unknown-unicast flooding, reply-based learning, and show mac address-table output.
- What you can do after
- Operate/configure Cisco IOS by viewing the MAC address table and clearing dynamic entries selectively or globally.
Read how Acing the CCNA Exam: Volume 1 Fundamentals and Protocols explains mac address table →
Acing the CCNA Exam: Volume 2 Advanced Networking and Security
A MAC address table is a switch data structure that maps learned MAC addresses to the ports through which their devices are reachable.
- How it is used
- Uses learned destination mappings to forward known unicast frames and flood frames whose destinations are absent from the table.
- How deep it goes
- Explains lookup, VLAN-scoped flooding, capacity exhaustion, and Port Security controls, but does not detail the complete learning algorithm.
- Examples
- Uses SW1, PC1, R1, spoofed frames, and Cisco verification output showing secure addresses and learned-port counts.
- What you can do after
- Diagnose unknown-unicast flooding and verify secure MAC entries and per-port learning limits with Cisco IOS commands.
Read how Acing the CCNA Exam: Volume 2 Advanced Networking and Security explains mac address table →
Related concepts
- known unicast frameused by · A known unicast frame is a unicast frame whose destination MAC address has an entry in the receiving switch's MAC address table.
- clear mac address-table dynamicconfigured by · clear mac address-table dynamic is a Cisco IOS command family for removing dynamically learned MAC addresses from a switch's MAC address table.
- show mac address-tableused by · show mac address-table is a Cisco IOS command that displays the MAC address table of a switch.
- network switchpart of · A network switch is a device that connects devices within a local network and selectively forwards data-link-layer frames to their intended destinations.
- port securityused by · Port security is a network-switch control that restricts a switch port to authorized device addresses or connection conditions and defines responses to violations.
- mac flooding attackused by · A MAC flooding attack is a Layer 2 attack that fills a switch's MAC address table with spoofed addresses so frames are flooded instead of selectively forwarded.
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