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    Services: DHCP server ip range round the wrong way.

    General pfSense Questions
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    • F
      firewalluser
      last edited by

      2.2-RELEASE (amd64)
      built on Thu Jan 22 14:03:54 CST 2015

      Services: DHCP

      Subnet Mask                Available range
      255.255.255.255 /32 x.x.x.250 - x.x.x.248 Are these two the right way round?
      255.255.255.254 /31 x.x.x.249 - x.x.x.248 Are these two the right way round?
      255.255.255.252  /30 x.x.x.249 - x.x.x.250

      TIA.

      Capitalism, currently The World's best Entertainment Control System and YOU cant buy it! But you can buy this, or some of this or some of these

      Asch Conformity, mainly the blind leading the blind.

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      • johnpozJ
        johnpoz LAYER 8 Global Moderator
        last edited by

        masks of 32 and 31 would not be viable masks on a dhcp scope..

        An intelligent man is sometimes forced to be drunk to spend time with his fools
        If you get confused: Listen to the Music Play
        Please don't Chat/PM me for help, unless mod related
        SG-4860 24.11 | Lab VMs 2.7.2, 24.11

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        • F
          firewalluser
          last edited by

          Should the GUI allow it?

          Capitalism, currently The World's best Entertainment Control System and YOU cant buy it! But you can buy this, or some of this or some of these

          Asch Conformity, mainly the blind leading the blind.

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          • johnpozJ
            johnpoz LAYER 8 Global Moderator
            last edited by

            Those are valid for setting the IP on your interface..  But not going to work with a dhcp scope on that interface.

            See attached..  Guess they could put in some check to invalidate dhcp scope when address on interface set with those sorts of masks..

            A mask of /32 is 1 address.. That specific address.. there is no IPs available at all for a dhcp server to hand out..  /31 is kind of special mask that could be used on point to point connections between say 2 routers for a transit network where 1 side had 192.168.1.2/31 and other hand 192.168.1.3/31 or .0 and .1 – but again that would not be valid for use with dhcp.

            Smallest scope would be /30

            So for example 192.168.1.0 would be the wire, .1 would be the interface and .2 would be 1 address available and .3 would be broadcast.

            borkeddhcpscope.png
            borkeddhcpscope.png_thumb

            An intelligent man is sometimes forced to be drunk to spend time with his fools
            If you get confused: Listen to the Music Play
            Please don't Chat/PM me for help, unless mod related
            SG-4860 24.11 | Lab VMs 2.7.2, 24.11

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            • F
              firewalluser
              last edited by

              /32 is the default mask for a new nic so I wonder if it might cause some problems for new users, thats where I am coming from.

              Is there any reason for /32 to be the default for a new nic?
              Any advantages/disadvantages in changing the default to say /30 or even /24, to avoid dhcp scoping issues?

              Depends on the target audience I guess, although I see advantages in using small ip address ranges.

              Capitalism, currently The World's best Entertainment Control System and YOU cant buy it! But you can buy this, or some of this or some of these

              Asch Conformity, mainly the blind leading the blind.

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              • johnpozJ
                johnpoz LAYER 8 Global Moderator
                last edited by

                If users do not understand what the mask to set on their interface they really should not be creating new interfaces ;)

                /32 is not the default to be honest, that is just the first item in the drop list you can pick from.. Should they have the list sorted the other direction and make it /1 ?

                An intelligent man is sometimes forced to be drunk to spend time with his fools
                If you get confused: Listen to the Music Play
                Please don't Chat/PM me for help, unless mod related
                SG-4860 24.11 | Lab VMs 2.7.2, 24.11

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                • F
                  firewalluser
                  last edited by

                  If users do not understand what the mask to set on their interface they really should not be creating new interfaces ;)

                  Its another thing to be aware of as its changed behaviour from earlier versions, I saw it and wondered what it would do to the dhcp page more than anything else, but irrespective of above, I reckon given time it will trip a few users up.

                  /32 is not the default to be honest, that is just the first item in the drop list you can pick from.. Should they have the list sorted the other direction and make it /1 ?

                  I dont think reversing the sort order is neccesary, but it would be useful if it could default to a common subnet mask imo.

                  Sometimes common configuration mistakes can become exploitable and whilst I dont expect this to be a problem, I dont know what else it might cause problems for. Until I poke around a bit more it might be just a blind alley and nothing to worry about.

                  Capitalism, currently The World's best Entertainment Control System and YOU cant buy it! But you can buy this, or some of this or some of these

                  Asch Conformity, mainly the blind leading the blind.

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                  • johnpozJ
                    johnpoz LAYER 8 Global Moderator
                    last edited by

                    "but it would be useful if it could default to a common subnet mask imo."

                    And who says what is common.. is /24 common?  Maybe to you - but to others maybe they always use /25 when bringing up a new segment..  You have no idea what a user might be creating a interface for..  To assume /24 solves nothing - if the user doesn't understand what the mask is in the first place..

                    Put in a feature request if you would like the drop down to start on /24 for new interfaces for ipv4, and /64 for ipv6 since drop down on that one is /128

                    An intelligent man is sometimes forced to be drunk to spend time with his fools
                    If you get confused: Listen to the Music Play
                    Please don't Chat/PM me for help, unless mod related
                    SG-4860 24.11 | Lab VMs 2.7.2, 24.11

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