What's changed: Initial version
4.4Basic switching concepts
Covers the MAC address table by which a switch learns a source MAC and its receive port, flooding for unknown/broadcast frames, the default 300-second aging, MAC address filtering for permit control, and the VLAN that divides an L2 broadcast domain—learned while glancing at show mac address-table as the basics of "how a switch learns and delivers to a destination."
A switch does not know from the start where its connected devices are. Watching traffic, it gradually learns "which MAC-address device is beyond which port" and uses that table to deliver frames only to the correct port. This learning mechanism is the MAC address table. This section covers the table's learning, flooding when the destination is unknown, aging that removes stale entries (default 300 seconds), MAC address filtering for permit control, and the VLAN that logically divides one switch—learned while glancing at show mac address-table output as the basics of "how a switch learns and delivers to a destination."
4.4.1MAC address table: learning and behavior
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