Why hub doesn't send the signal on the same interface it received?

Why hub doesn’t send the signal on the same interface it received ?
I know the concept but need a simple language answer for this question. Thanks.

Hi Nitesh K,

If I try to understand well your question, you want to know why the hub doesn’t send and receive a frame at the same time.
If this is your question, so the easy way to explain how the hub works is the example of the walkie-talkie where only 1 person on 1 device is able to speak while the other person on the 2nd device is listening, then when the 1st person finish speaking then the 2nd person can start speaking. In other words, they can’t speak and listen at the same time. This is what we call a half-duplex communication.

Same applies on hubs as well as repeaters, both work as half-duplex in their data transmission/receive.

Hope I could answer your question.

Thanks but my question was ‘why does hub/Switch doesn’t send the signal back to the same port ?’
Actually I know they don’t work that way but I was asked that que in an interview.

Hi Nitesh,

I got your question now.

Normally a LAN has a physical topology (which is the way the network looks like), and Logical Topology (which is the way that the frame takes to reach the destination).

When using a hub, the physical topology is always a star because you have 1 hub in the middle and all PC’s are connected to it.

As per the logical topology, the data takes a bus topology to reach to its destination and that’s why the hub won’t send the data back to the port that it was received on.
The best way to explain it is to see the picture attached (source: http://www.datacottage.com/nch/eoperation.htm#.V-Uf_cWaKVY)

Does it make sense now?