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The unicast-flood process on R5000 devices units is the following: if the frame's destination MAC-address is not included in the unit's MAC switch forwarding table, then this frame is flooded to all interfaces besides the sender interface. The distribution occurs until the unit receives a frame with this MAC-address as the sender (i.e., the interface to which the frame was destinated to respond). After that, the R5000 will learn: it will add this MAC address to the MAC switch forwarding table and map it with the interface from which it was received. If the R5000 does not learn in 4 seconds, and frames still arrive, then traffic to this direction will be blocked for 4 seconds. Then the process repeats.
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