The query for allocating external IPs from an IP Pool range currently generates the sequence of all IPs in that range. That's inefficient, but works at this point. However, there's a latent bug here. That generates the sequence of IP addresses by computing offsets, using generate_series(0, last_address - first_address), and adding those offsets to the first address. That subtraction will not fit in an i64 if the address range is huge. For example:

demo@127.0.0.1:26257/movr> select 'fd00::'::INET - 'fc00::'::INET;
ERROR: result out of range
SQLSTATE: 22003
demo@127.0.0.1:26257/movr>

That's not super likely, but it should be detected and handled correctly, by taking the maximum allowed offset from the first address. Something like:

demo@127.0.0.1:26257/movr> select if('fc00::'::INET + 9223372036854775807 > 'fd00::'::INET, 'fd00::'::INET, 'fc00::'::INET + 9223372036854775807) - 'fc00::'::INET;
       ?column?
-----------------------
  9223372036854775807
(1 row)


Time: 0ms total (execution 0ms / network 0ms)

demo@127.0.0.1:26257/movr>

That constant is i64::MAX, and can be supplied on the Rust side or in the database. The IF is needed because there's no maximum function for INET types.