FreeBSD / OpenBSD: PF Firewall Filter Large Number Of Subnets and IP Address

The PF (Packet Filter) firewall in FreeBSD and OpenBSD is a powerful tool for controlling network traffic on your system. If you need to filter a large number of subnets and IP addresses, you can use the table feature of PF to create a list of subnets and IP addresses that you want to allow or block.

Here is an example of how you can use the table feature to filter a large number of subnets and IP addresses:

1. Create a file that contains the list of subnets and IP addresses you want to filter. Each subnet or IP address should be on a separate line. For example:

10.0.0.0/8
192.168.0.0/16
172.16.0.0/12
1.2.3.4
5.6.7.8

2. Load the list into a PF table using the table keyword and the file option. For example:

table <mytable> file:/path/to/my/table.txt

3. Use the block or pass keyword to block or allow traffic from the subnets and IP addresses in the table. For example, to block traffic from the subnets and IP addresses in the table:

block in quick from <mytable>

To allow traffic from the subnets and IP addresses in the table:

pass in quick from <mytable>

4. Save the changes to the PF configuration file and apply the new rules:

pfctl -f /etc/pf.conf
pfctl -e

This will apply the new rules and block or allow traffic from the subnets and IP addresses in the table.

Keep in mind that the syntax for the table feature and the block and pass keywords may vary depending on your version of PF and your specific needs. For more information on using the table feature and other advanced features of PF, you can refer to the PF documentation or the man pages for the pfctl and pf.conf commands.