ip-range-to-CIDR

Convert IP address range to CIDR.

Examples

% ip-range-to-cidr 192.168.0.0 192.168.0.255
192.168.0.0/24

Figuring out github.com's AS range:

% systemd-resolve github.com                                                                                          
github.com: 140.82.118.3                       -- link: phy0

-- Information acquired via protocol DNS in 45.6ms.
-- Data is authenticated: no

 % openrdap-client --json --type ip 140.82.118.3 | jq -r '"\(.startAddress) \(.endAddress)"' | xargs ./ip-range-to-cidr
 140.82.112.0/20