I would use "space-separated".
To avoid the introductory word with an immediate pause:
A simpler way to express this is with a space-separated list of ranges:
You only want 1 addresses in each subnet to have the real subnet mask. As the example shows, you can have addresses in 2 or more subnets, as separate ranges. So if you're in 18.104.22.168/28, and 22.214.171.124/28, you'd do: inet 126.96.36.199-29/28 inet 188.8.131.52-61/28 or similar.
You could do 184.108.40.206-61/28 or something, and all of the extra addresses would be /32s. However, you wouldn't be able to reach other hosts in the 2nd subnet directly, since you have no route in that subnet.
However, I think this is beyond the scope of the handbook.
The blank line between the </programlisting> and </sect1> should be removed. Unless it was in the original, phabricator is making it hard to tell.