Following scenario

+-----------+              +-----------+
| Network A |--- Router ---| Network B |
+-----------+              +-----------+


If a client in 'Network A' wants to connect to 'Network B' it needs the IP of the router as default gateway to acquire the MAC of the router via ARP. (?)

If the client in 'Network B' answers the request (of client in 'Network A') it doesn't need a default gateway because the MAC of the router is in the request packet. (?)

Are this two statements correct?

Thank you, nodna

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin
    Aug 15 '17 at 4:25

The first statement is correct. Every device in a network needs to know the default gateway IP address in order to be able to send packets to another network.

The second one isn't true, because when the device in network B inspects the IP layer, it finds that the source IP adddress belongs to network A. So it will try to send the reply through its own default gateway and if it doesn't know the default gateway IP, it will discard the packet.

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