Have you ever wondered how to use iptables to block IP range?

IP blocking is an improved security measure. We can use iptables to block a certain IP address or range of hostile IP addresses.

At Bobcares, we often receive requests to block IP addresses as part of Server Management Services.

Today let’s check how to easily block IP addresses using iptables.

Why block Iptables in range?

Sometimes, undesired connections occur to our server from an IP address or a range of IP addresses.

In such cases, we usually block those IP addresses to ensure better security. In Linux servers, we can use iptables for this purpose.

More about iptables

Iptables is a flexible firewall utility for Linux operating systems. This will allow or block certain connections to the server.

Generally, iptables use three chains: input, forward and output.

Input and output chains for controlling the behavior of incoming and outgoing connections respectively. Using the forward chain, we can control incoming connections that aren’t being delivered locally.

We then configure policies based on the behavior of these three chains.

With the default chain policies configured, we can start adding rules to iptables. This enables it to know what to do when it encounters a connection from a particular IP address.

So, there are three basic responses, Accept, Reject and Drop. Among these, we use the drop command to block the IP range.

How to block IP range using iptables?

So far we have discussed the IP blocking in iptables. Let’s now see how our Support Engineers block IP ranges in iptables.

Recently, one of our customers approached us to block a range of IP addresses with something like 2xx.3x.1xx.*, etc. He used the command,

iptables -A INPUT -s 2xx.3x.1xx.12x -j DROP

This command can block the specified IP address. But, it will not satisfy his requirement of blocking a range of IP addresses.

So, in order to block the given range of IP addresses, our Support Engineers used the following command.

iptables -A INPUT -s 2xx.3x.1xx.0/24 -j DROP

We also use the command  to block the range of IP addresses

iptables -A INPUT -m iprange --src-range 2xx.3x.1xx.0/24 -j DROP

To block a specific range of IP from 2xx.3x.1xx.125 to 2xx.3x.1xx.225. We use the command

iptables -A INPUT -m iprange --src-range 2xx.3x.1xx.125-2xx.3x.1xx.225 -j DROP

Similarly, to block 216.3x.*.* addresses:

iptables -A INPUT -s 216.3x.0.0/16 -j DROP

Also, to block 216.*.*.* addresses, we use the command,

iptables -A INPUT -s 216.0.0.0/8 -j DROP

[Need more help to block IP addresses using iptables?- We’ll help you.]

Conclusion

In short, we block a certain hostile IP address or range of IP addresses to improve security. In today’s article, we also discussed how our Support Engineers block a specified range of IP addresses for our customers.