Friday, 25 January 2013

What will happen in this basic networking subnet case ?

We have two PC with switch in between

PC1----------------------------------------------------------Switch-------PC2 ( netmask
( netmask

Will they ping each other ?

What I am changing here ?

I am changing the subnet mask of the PC , so that they are in different broadcast domains.

Let me know what you think ?


  1. I think they should be able to ping each other. What do you think ?? Thanks for the question.

  2. In my understanding, since subnet is different broadcast address will be different. As broadcast address are different ARP resolution will not happen and end result: ping will not go through.

  3. Thanks for your comments. The answer is , it will ping.

    The steps will be like this :

    1) From PC1 -> ping> first the PC will consult its routing table, which will say that the ip address belong to its own subnet , so it will send the ARP request.

    2) From PC1 ARP request will go to switch, switch will forward to PC2.

    3) PC2 receives it, as it is for its IP address , it will reply.

    4) The ARP will get resolved and the PC will start pinging with each another.

    This is a typical case and this is happening only because both has an overlapping range of IP address. The range 192,168.7.1- falls in both the subnets. If you take any other IP address , this will not happen because the routing table of PC will reject it, and instead of sending local ARP will send ARP to its gateway.



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