Does a layer 2 switch forward frame with no preference whether its an unicast broadcast or multicast on first come serve basis?

  • Can you expand on your question a little bit. The way it's written it seems like a homework question with no prior research done (i.e. Can you do my homework for me)
    – Zypher
    Jul 14, 2011 at 21:04
  • I did google a bit, but there's no direct answer. My own answer is no preference, because whether it's unicast or broadcast frame, the switch needs to look up FDB, if it's empty, it will flood out until it finds one destination for unicast; and to all destinations for broadcast. In terms of which one floods first it's first come first serve. Hope someone can confirm. Jul 14, 2011 at 21:43

2 Answers 2


"preference" is a little unclear, but generally speaking, there is not a "preference" assigned whether the frame is multicast, unicast, or broadcast.


A switch forwards frames to:

  • all appropriate ports if multicast/broadcast
  • all ports belonging to the same vlan in FORWARDING state when the switch does not know on which port the unicast destination MAC lies
  • the single correct port if on the same VLAN when knows on which port the unicast destination MAC lies

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