ipset is a companion application for the iptables Linux firewall. It allows you to setup rules to quickly and easily block a set of IP addresses, among other things.


Installation
Install the ipset package.

Configuration
Blocking a list of networks
Start by creating a new "set" of network addresses. This creates a new "hash" set of "net" network addresses named "myset".

# ipset create myset hash:net

or 

# ipset -N myset nethash

Add any IP address that you would like to block to the set.

# ipset add myset 14.144.0.0/12
# ipset add myset 27.8.0.0/13
# ipset add myset 58.16.0.0/15
# ipset add myset 1.1.1.0/24

Finally, configure iptables to block any address in that set. This command will add a rule to the top of the "INPUT" chain to "-m" match the set named "myset" from ipset (--match-set) when it is a "src" packet and "DROP", or block, it.

# iptables -I INPUT -m set --match-set myset src -j DROP

Blocking a list of IP addresses
Start by creating a new "set" of ip addresses. This creates a new "hash" set of "ip" addresses named "myset-ip".

# ipset create myset-ip hash:ip

or 

# ipset -N myset-ip iphash

Add any IP address that you would like to block to the set.

# ipset add myset-ip 1.1.1.1
# ipset add myset-ip 2.2.2.2

Finally, configure iptables to block any address in that set.

# iptables -I INPUT -m set --match-set myset-ip src -j DROP

Making ipset persistent
The ipset you have created is stored in memory and will be gone after reboot. To make the ipset persistent you have to do the followings:
First, save the ipset to /etc/ipset.conf:

# ipset save > /etc/ipset.conf

Then enable ipset.service, which works similarly to iptables.service for restoring iptables rules.

Warning: A (rare) bug FS#79674 has been observed once which resulted in iptables.service failing due to missing ipsets despite ipset.service succeeding. Use redundant security and consider a monitoring script if you need 100% assurance that your firewall is intact.
Blocking with PeerGuardian and other blocklists
The pg2ipset-gitAUR tool by the author of Maeyanie.com, coupled with the ipset-update.sh script, can be used with cron to automatically update various blocklists. Currently, by default, blocking of: country, tor exit node and Bluetrack pg2 list are implemented.

Other commands
To view the sets:

# ipset list

or

# ipset -L

To delete a set:

# ipset destroy myset

or 

# ipset -X myset

To delete all sets:

# ipset destroy

Please see the ipset(8) for further information.

Optimization
The iprangeAUR tool can help to reduce entries in ipset.conf by merging adjacent ranges or eliminating overlapped ranges. This can improve the router/firewall performance if the table size is huge. This tool can also convert a list of hostnames to IPs.
Although ipset is designed to be able to scale well, that does not mean infinitely. In particular, some nations have very large IP address spaces, which will cause geoblocking to be inefficient.