Friday, 25 January 2013

What will happen in this basic networking subnet case ?


We have two PC with switch in between

PC1----------------------------------------------------------Switch-------PC2 ( 192.168.7.1 netmask 255.255.0.0)
(192.168.7.10 netmask 255.255.255.0)

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 ?

3 comments:

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

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  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.

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

    The steps will be like this :

    1) From PC1 -> ping 192.168.7.10-> 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 192,168.7.1-192.168.7.254 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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