CIDR addition / subtraction calculator. Maybe useful for setting route tables when metrics are not available (e.g. wireguard next-hop)
> let univ = ::/0
> univ - 2001:da8::/56
[
::/3
2000::/16
2001::/21
2001:800::/22
2001:c00::/24
2001:d00::/25
2001:d80::/27
2001:da0::/29
2001:da8:0:100::/56
...