IPv4 Private Address Space

Rudy Zijlstra rudy at grumpydevil.homelinux.org
Tue May 11 22:12:17 UTC 2021



On 12-05-2021 00:04, Louis Garcia wrote:
> On Tue, May 11, 2021 at 5:51 PM Thor Simon <Thor.Simon at twosigma.com> wrote:
>> What exactly are you trying to do?  There is not a /12 (255.240.0.0 netmask) of addresses available starting at 172.16.4.0 -- you have given the mask and broadcast address for the entire 172.16.0.0/12 containing range, but your subnet address is offset from the start of the containing netblock by 1024 addresses.  The DHCP server is entirely right to reject this nonsensical configuration.
>>
>> Do you have an existing /22 at 172.16.0.0 that you're trying to work around?
>>
>> T
> Currently I have three networks 172.16.2.0/24 172.16.3.0/24
> 172.16.4.0/24. I read that not all of 172.16.0.0 is private, only
> 172.16.0.0/12. I am trying to not have public routable IPs on my
> network. Please let me know if this setup is fine.
>
>            # DHCP Server Configuration file.
>
>            authoritative;
>            default-lease-time 600;
>            max-lease-time 7200;
>
>            # Client system architecture type: RFC4578
>            option arch code 93 = unsigned integer 16;
>
>            subnet 172.16.2.0 netmask 255.255.255.0 {
>                        option domain-name-servers 172.16.2.1;
>                        option broadcast-address 172.16.2.255;
>                        option routers 172.16.2.1;
>                        option ntp-servers 172.16.2.1;
>                        range 172.16.2.50 172.16.2.254;
>                        if option arch = 00:07 {
>                              filename "/grub/shim.efi";
>                        }
>                        next-server 172.16.2.5;
>            }
>
>            subnet 172.16.3.0 netmask 255.255.255.0 {
>                        option domain-name-servers 172.16.3.1;
>                        option broadcast-address 172.16.3.255;
>                        option routers 172.16.3.1;
>                        option ntp-servers 172.16.3.1;
>                        range 172.16.3.50 172.16.3.254;
>            }
>
>            subnet 172.16.4.0 netmask 255.255.255.0 {
>                        option domain-name-servers 172.16.4.1;
>                        option broadcast-address 172.16.4.255;
>                        option routers 172.16.4.1;
>                        option ntp-servers 172.16.4.1;
>                        range 172.16.4.50 172.16.4.254;
>            }
This one should work, yes

Rudy



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