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I remember reading somewhere that switches defined "data link layer broadcast domains": that is, data link broadcasts from one network connected to the switch are not forwarded to the others.

If this is true, what happens when a host directly connected to a switch makes an ARP request? Does it go beyond the switch?

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up vote 2 down vote accepted

In the case of a basic switch -- that is, without getting into VLANs and so-called "layer-3 switches" -- the switch is NOT the edge of a broadcast domain. ARP broadcasts, like all broadcasts, are sent to all ports of the switch.

You may have heard that switches separate collision domains, which is true, but is a separate concept from broadcast domains.

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