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Which of the following is NOT true with respect to a transparent bridge and a router?

  1. Both bridge and router selectively forward data packets
  2. A bridge uses IP addresses while a router uses MAC addresses
  3. A bridge builds up its routing table by inspecting incoming packets
  4. A router can connect between a LAN and a WAN

My attempt :

Option (2) is false, since bridge uses MAC address as it' working at layer 2, and router uses IP address as, it's working at layer 3.

Option (3) is false, since a Bridge will not create routing table . It's created by Router . Bridges keep a table of destination addresses and outbound interfaces


Can you explain it in a formal way, please?

  • Didn't downvote, but this looks like a homework question. If this is the case, we'd like to see that mentioned in the question. Also, homework questions tend to be hypothetical; such questions are discouraged here as well. For more information, see the help center. – bwDraco Sep 17 '16 at 5:32
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Both bridge and router selectively forward data packets

Not quite sure what they meant by "selectively" (ports chosen based on a table? packets dropped based on filter rules?) but all those things happen, so I suppose this one is true.

A bridge uses IP addresses while a router uses MAC addresses

Not true. Routers primarily use IP addresses, while bridges usually don't look at IP at all.

A bridge builds up its routing table by inspecting incoming packets

It's not really called a "routing" table (afaik the more common name is FDB??), but in the end, it's still used for the same purpose – to decide which packet goes out which port – and it is built that way. So this is 98% true.

A router can connect between a LAN and a WAN

True, that's a common usage.

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