Netgate Discussion Forum
    • Categories
    • Recent
    • Tags
    • Popular
    • Users
    • Search
    • Register
    • Login

    Learning about network subsets - Overlapping addresses?

    Scheduled Pinned Locked Moved General pfSense Questions
    4 Posts 4 Posters 763 Views
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • F
      FroToast
      last edited by

      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>

      1 Reply Last reply Reply Quote 0
      • DerelictD
        Derelict LAYER 8 Netgate
        last edited by

        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.

        Chattanooga, Tennessee, USA
        A comprehensive network diagram is worth 10,000 words and 15 conference calls.
        DO NOT set a source address/port in a port forward or firewall rule unless you KNOW you need it!
        Do Not Chat For Help! NO_WAN_EGRESS(TM)

        1 Reply Last reply Reply Quote 0
        • C
          coxhaus
          last edited by

          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.

          1 Reply Last reply Reply Quote 0
          • K
            kpa
            last edited by

            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

            1 Reply Last reply Reply Quote 0
            • First post
              Last post
            Copyright 2025 Rubicon Communications LLC (Netgate). All rights reserved.