Why does “2605:cb80:1:9800::1/56” or “2605:cb80:3:1000::/56” work when adding to OSPFv3 Area Range, but “2605:cb80:3:11X0::/56” does not and generates a “Error in Range -ipv6 network address expected!”
Where X equals any number 1-9.
(X can be 1-F and cause the issue, not just 1-9)
Because all non-prefix bits must be zero when defining/referring to a network prefix.
The nibble you’re specifying is not included in the 56 most significant (leftmost) bits, so it must be zero.
It’s the same reason that saying 192.168.1.0/23 is invalid as a prefix definition.
192.168.0.0/23 is valid (192.168.1.0 is a HOST inside of this prefix)
192.168.2.0/23 is valid (this is the next valid network prefix after the previous one)
2605:cb80:3:1100::/56 → this prefix allows its owner to define their own networks from it in the range of:
2605:cb80:3:1100:0000:0000:0000:0000 through
2605:cb80:3:11ff:ffff:ffff:ffff:ffff
Note that your X falls inside the range of freedom…
If you want to define a range where that nibble is non-zero, then you must use a /60…
(or certain even values if using /57 - /59 but it’s generally considered best to just use nibble-boundary masks)
Thank you for clarifying! Clearly I need to brush up on IPv6 and restructure my IPv6 addressing.