Learning about network subsets - Overlapping addresses?



  • Hello,

    So first of all, I'm not certain which topic this subject belongs to so I apologize in advance.

    I've been having a hard time finding a straight forward answer to my question so I would be grateful if you would give me advice on this matter.

    I've been told that subnets divided in such a way that you segment part of the 32-bit network address to mean the network, and the other half to mean host address? IE: (<network><host>)

    In this sense is it possible to have an IP address - say for instance 125.125.3.3 - in the subnet of 125.125.3.3/24 and another same address in the subnet of 125.125.3.3/16?'
    If so, would these two addresses be mutually exclusive?

    Needless to say, networking isn't my profession, but I would still love to learn all about it. So, I would very much appreciate any advice or resources you would give me.  :)

    Thanks in advance,
    Michael L.</host></network>


  • LAYER 8 Netgate

    No.

    If a host in subnet 125.125.0.0/16 tried to contact a host in 125.125.3.3/24 it would think it is on its local subnet and not try to route it to the gateway.

    Be careful to distinguish between routes and subnets.

    If a router has the following two routes:

    192.168.3.0/24 to gateway 10.10.10.1
    192.168.0.0/16 to gateway 10.10.10.2

    That will work because the route with the longest mask will get the traffic.



  • Subnetting and superscoping are ways to address groups of IP addresses instead of individually.  It makes for less code which makes it faster.  There are a few gotcha  like every network has a network address and a broadcast address which can be overlaid on a larger address space.  You just need to be aware of it.



  • There's a nice CIDR/subnet calculator online that shows you exactly what addresses are part of a particular subnet and the details of the subnet in address/CIDR/netmask notations.

    http://www.subnet-calculator.com/cidr.php


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