On a Cisco Catalyst switch, which command displays the MAC address forward/filter table (the Layer 2 CAM table)?
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Ashow mac filter
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Bshow run
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Cshow mac address-table
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Dshow mac filter-table
Answer
Correct Answer: show mac address-table
Explanation
Introduction / Context:Switches maintain a Content Addressable Memory (CAM) table—often called the MAC address table—to map MAC addresses to ports for efficient forwarding. Troubleshooting Layer 2 connectivity frequently requires viewing this table.
Given Data / Assumptions:
- Environment: Cisco IOS/Catalyst syntax.
- Goal: Display the learned MAC entries and associated interfaces/VLANs.
Concept / Approach:On modern Cisco switches, the command is show mac address-table. Older platforms might use show mac-address-table, but the commonly accepted form in IOS is as shown. Other listed commands are invalid or serve different purposes.
Step-by-Step Solution:
Recall the feature name: MAC address table (CAM).Match it to the IOS show command: show mac address-table.Exclude unrelated commands like show run (configuration), and non-existent syntaxes like show mac filter or show mac filter-table.Verification / Alternative check:Issuing show mac address-table dynamic displays dynamically learned entries by VLAN and port.
Why Other Options Are Wrong:show run: Shows configuration, not learned MACs. show mac filter / show mac filter-table: Not standard IOS commands for MAC learning.
Common Pitfalls:Confusing ARP tables (Layer 3) with MAC tables (Layer 2). ARP is viewed on routers/Layer 3 SVI with show arp.
Final Answer:show mac address-table