This will allow you generate a filter list based on live registry data.
You can also use a regular 'whois' client against filtergen.dan.me.uk to get the same output.
For example, on a UNIX-based operating system such as FreeBSD:
whois -h filtergen.dan.me.uk -- "-6 -RIPE -t cisco -f example -upto 48 AS57672
Note: to remove comments, append " | grep -v ^%" to the command.
% % Filter List Generator % Copyright(c) 2024, Daniel Austin MBCS % % usage: % [-D] [-6] [-RIPE | -RADB | -APNIC] [-f filtername -t filtertype [-upto N]] as-set % % -D for DEBUG mode (shows working calculations) % -6 for IPv6 filter generation % -RIPE for whois.ripe.net lookups % -RADB for whois.radb.net lookups % -APNIC for whois.apnic.net lookups % -f will generate a cisco-style filterlist called 'filtername' (use -t filtertype as follows) % cisco (default) % iox-xr % juniper (basic support) % force10 % mikrotik % Additionally, if using -f/-t you may specify -upto N where N is the prefix size to permit up-to % % Using whois.radb.net for lookups % Generating filter list for 'AS2818' 132.185.0.0/16 132.185.128.0/20 132.185.132.0/24 132.185.144.0/20 132.185.144.0/24 132.185.145.0/24 132.185.146.0/24 132.185.147.0/24 132.185.148.0/24 132.185.149.0/24 132.185.150.0/24 132.185.151.0/24 132.185.152.0/24 132.185.153.0/24 132.185.154.0/24 132.185.155.0/24 132.185.156.0/24 132.185.157.0/24 132.185.158.0/24 132.185.159.0/24 132.185.240.0/20 132.185.240.0/24 132.185.241.0/24 132.185.242.0/24 132.185.243.0/24 132.185.244.0/24 132.185.245.0/24 132.185.246.0/24 132.185.247.0/24 132.185.248.0/24 132.185.249.0/24 132.185.250.0/24 132.185.251.0/24 132.185.252.0/24 132.185.253.0/24 132.185.254.0/24 132.185.255.0/24 212.58.224.0/19 212.58.224.0/20 212.58.224.0/24 212.58.225.0/24 212.58.226.0/24 212.58.227.0/24 212.58.228.0/24 212.58.229.0/24 212.58.230.0/24 212.58.231.0/24 212.58.232.0/24 212.58.233.0/24 212.58.234.0/24 212.58.235.0/24 212.58.236.0/24 212.58.237.0/24 212.58.238.0/24 212.58.239.0/24 212.58.240.0/20 212.58.240.0/24 212.58.241.0/24 212.58.242.0/24 212.58.243.0/24 212.58.244.0/24 212.58.245.0/24 212.58.246.0/24 212.58.247.0/24 212.58.248.0/24 212.58.249.0/24 212.58.250.0/24 212.58.251.0/24 212.58.252.0/24 212.58.253.0/24 212.58.254.0/24 212.58.255.0/24 % end of filter list for 'AS2818' (72 prefixes found) % took 0.33 secs for query (0.21 secs of connection time) % used 1 connections -- 217 lines of whois data parsed