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Diagram

From my understanding:

  • If a ping request is passed to another computer through the hub, the ping request can be seen by all 5 computers on the network
  • If a ping request is passed to another computer on the same network (pc1 and pc2, pc3, pc4 and pc5) then the ping request can only be seen by the computer that sends it and the computer that receives the request
  • If a ping request is passed to another computer through the switch, then the ping request can only be seen by the computer that sends it and the computer that receives the request

As a result:

  • PC1 pinging PC2 will show the ping request on both computers
  • PC1 pinging PC5 will show the pin request on all computers (since they have to pass through a hub)
  • PC4 pinging PC1 will show the ping request on all computers (since they have to pass through a hub)

Am I on the right track? Or is it the case that if a ping request has to pass through a hub, it is not the case that all computers see it because of the ARP request?

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  • Hub always transferres a packet to all ports except the port a packet come from. Without exclusions. Or it is not a hub. So a ping packet sent to the net by any station to any address (including non-existing ones) is seen by all another stations connected to the hub this ping packet walked through.
    – Akina
    Commented Aug 10, 2018 at 5:18
  • @Akina What do you mean by port? If PC1 sends a ping request to PC5, it would travel to the hub. As a result it would be sent to all other stations connected to the hub except the "port" the packet came from. By port, do you mean individual computer or computers connected to the same network? Eg PC1 pings PC5 so the ping request would be seen by PC3, PC4 and PC5 or is it PC2, PC3, PC4, PC5?
    – McJeremyFace
    Commented Aug 10, 2018 at 5:26
  • What do you mean by port? A physical port on the hub, of course. A hole on the hub where a patch-cord connector is plugged in. do you mean individual computer or computers connected to the same network? It is L2, no (sub)networks exists on it.
    – Akina
    Commented Aug 10, 2018 at 5:30

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There are 2 different parts to this question -

Ping sends a packet and gets a response (or occasionally multiple responses - normally thats bad). Like all other traffic, this request is seen by all devices that it passes through (but typically they don't respond). If you do a traceroute, that shows all the routers in the path, and thats a fair (but not full) approximation of the systems which see the packet.

A hub is old technology which sends data on the lan to all systems connected through it. Thus if you do a ping and you are using a hub, all computers on the LAN will see it - but won't respond. If you are using a switch - which is the non-ancient version of a hub, and much more common, only the switch and routers will see the request.

(I do note that some switches have mirror ports, those mirror ports can also see packets)

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  • Ok thanks. I dont' get one thing at the moment though. If PC1 and PC2 are on the same LAN, and they are connected to PC3 and PC4 through a hub, which PCs will receive the ping request when PC1 pings PC4? Now, since it is a hub, the ping request can be seen by all computers on the network, but does that include PC2 aswell? I assume the hub wont' send the packet back to the original PC1 + PC2 LAN?
    – McJeremyFace
    Commented Aug 10, 2018 at 7:53
  • I wonder what your understanding of a hub is. If PC1 and PC2 are on the same lan, and PC3 and PC4 are connected through a HUB, PC1,PC2,PC3 and PC4 are all on the same LAN.
    – davidgo
    Commented Aug 10, 2018 at 7:57
  • If PC1 and PC2 are connected to a switch, which then connects to a hub with PC3 and PC4 on it if PC1 pings PC4 then PC3 and PC4 will see the request, but not PC2.
    – davidgo
    Commented Aug 10, 2018 at 7:58

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