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

    Does pfsense support /31 bit mask?

    Scheduled Pinned Locked Moved General pfSense Questions
    7 Posts 4 Posters 1.8k 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.
    • C
      coxhaus
      last edited by

      This is more of a curiosity.  I have pfsense connected to my Cisco layer 3 switch using a /30 bit mask.  I wonder if I can use a /31 bit mask?

      1 Reply Last reply Reply Quote 0
      • bingo600B
        bingo600
        last edited by

        @coxhaus:

        This is more of a curiosity.  I have pfsense connected to my Cisco layer 3 switch using a /30 bit mask.  I wonder if I can use a /31 bit mask?

        An /30 IP network (takes up 4 addresses) consists of :

        0: Net address (the lowest)  - MUST HAVE
        1: device1  (one end of the ip link)
        2: device2  (other end of the ip link)
        3: Broadcast adress (the highest) - MUST HAVE

        A /31 IP network (takes up 2 addresses)  consists of :

        0: Net address (the lowest)  - MUST HAVE
        2: Broadcast adress (the highest) - MUST HAVE

        Technically it should be "legal" , but how many devices can you connect within that IP Network

        /Bingo

        If you find my answer useful - Please give the post a 👍 - "thumbs up"

        pfSense+ 23.05.1 (ZFS)

        QOTOM-Q355G4 Quad Lan.
        CPU  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
        LAN  : 4 x Intel 211, Disk  : 240G SAMSUNG MZ7L3240HCHQ SSD

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

          In a point to point network you don't need a broadcast IP.  I was thinking of trying it if pfsense supported it.  I am changing out my layer 3 switch for another model.

          1 Reply Last reply Reply Quote 0
          • jimpJ
            jimp Rebel Alliance Developer Netgate
            last edited by

            Yes, and it has for a long time:

            https://redmine.pfsense.org/issues/4190

            Remember: Upvote with the 👍 button for any user/post you find to be helpful, informative, or deserving of recognition!

            Need help fast? Netgate Global Support!

            Do not Chat/PM for help!

            1 Reply Last reply Reply Quote 0
            • bingo600B
              bingo600
              last edited by

              @coxhaus:

              In a point to point network you don't need a broadcast IP.  I was thinking of trying it if pfsense supported it.  I am changing out my layer 3 switch for another model.

              Whoopzz  :-[  - Did not know RFC 3021

              Thanx for making me learn something new today  ;)

              /Bingo

              If you find my answer useful - Please give the post a 👍 - "thumbs up"

              pfSense+ 23.05.1 (ZFS)

              QOTOM-Q355G4 Quad Lan.
              CPU  : Core i5 5250U, Ram : 8GB Kingston DDR3LV 1600
              LAN  : 4 x Intel 211, Disk  : 240G SAMSUNG MZ7L3240HCHQ SSD

              1 Reply Last reply Reply Quote 0
              • H
                Harvy66
                last edited by

                @bingo600:

                @coxhaus:

                In a point to point network you don't need a broadcast IP.  I was thinking of trying it if pfsense supported it.  I am changing out my layer 3 switch for another model.

                Whoopzz  :-[  - Did not know RFC 3021

                Thanx for making me learn something new today  ;)

                /Bingo
                [/quote]

                Been there, done that. I love learning.

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

                  Me too.  I just learned about it recently.  I thought I might try it.

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