ipset is a more efficient way to deal
with large numbers of IPs or Mac addresses with Netfilter/IPTables. The
only similar module IPtables has is
iprange, which may not be
applicable for all situations.
In this example, we’ll be blocking known Chinese address blocks.
Creating a set
I’ll create a set called “country_cn” and add CIDR blocks to it.
ipset --create country_cn nethash
nethash is the type of set appropriate for CIDR-formatted IP blocks.
If you only had IP addresses, you’d use
iphash. There are many others.
Adding IPs to the set
for IP in $(curl http://ipdeny.com/ipblocks/data/countries/cn.zone); do
ipset --add country_cn $IP
Using the set
iptables -A INPUT -m set --match-set country_cn src -j DROP
Editing the set
# Listing IPs
ipset --list country_cn
# Removing IPs
ipset --del country_cn 18.104.22.168/16
# Flushing set
ipset --flush country_cn
# Deleting set
ipset --destroy country_cn