What is IP forwarding and how does it work? (Brief Guide of USA)

Have you ever heard of IP forwarding? Probably not, but it is a very important process that allows your computer to communicate with other devices on a network. In this blog post, we will discuss what is IP forwarding and how it works. We will also provide some examples of how IP forwarding can be used to improve your networking experience. Stay tuned! Have look at our detailed guide on how to find your IP address.

How does IP forwarding work?

The IP forwarding algorithm is a sort of routing for IP networks that have been developed. To select a next-hop router as the next destination for a data packet, the algorithm utilizes a routing table. The next-hop address of the router that was selected is known as the IP address.

What does IP forwarding do?

The process of determining a packet’s or datagram’s potential route is known as IP forwarding. The method for routing packets is to use the information contained in them. Internet transmission is made by sending a packet from one network to another. To isolate networks, routers are utilized.

How to enable IP forwarding on Linux (IPv4 / IPv6)?

A switch can examine incoming traffic on one of its interfaces, determine that it is not intended for the system itself, but should be forwarded to another network, and then dispatched appropriately.

IP Forwarding is usually disabled by default in any recent Linux distributions. As a result, it’s a good idea to enable forwarding if we’re setting up a Linux router/gateway, a VPN server, or simply a plain dial-in server since many users will not require IP Forwarding.

In this article, we’ll learn how to enable IP forwarding on Linux and make it temporary or permanent on the system. This is a simple process that we will also explore. To be precise, a router is an entity that performs packet forwarding. The operation of routing or more generally routing through other networks is known as IP forwarding (IP redirection) and allows for the functioning of an operating system (here on Linux) as if it were a router.

IP forwarding is activated frequently when monitoring the network (particularly in a Man in the Middle Attack), but it’s also useful for simply setting up a Linux computer as a router to connect several networks.

Let’s check out how to Enable IP Forwarding:

To begin, we must verify whether the current IP forwarding is enabled.

Check whether IP Forwarding is turned on or not:

If IP forwarding is enabled, we may use the following lines to verify this: We can obtain the same information by querying the sysctl kernel value net.ipv4.ip_forward: If you want to check if IP forwarding has been enabled on your system, run these commands in a terminal or command prompt:

sysctl net.ipv4.ip_forward

net.ipv4.ip_forward = 0

Or verify the value in /proc system:

cat /proc/sys/net/ipv4/ip_forward


Temporary Activation

For both IPv4 and IPv6, the IP forwarding feature is controlled via /proc files. The following are examples of “/proc/sys/net/ipv4/ip_forward” for IPv4 and “confAllForwarding” for IPv6 from the “/proc/sys/, system, net, netfilter variables”.

When there are no errors in the logs, a closer look at these files reveals that they are set to 0 by default and may be adjusted to 1 temporarily. The file can then be modified or the “sysctl” command may be used:

| sysctl -w net.ipv4.ip_forward=1

Use the following command to reset your CRM’s temporary passwords: The parameters, however, will reset to their original state when the system restarts or “sysctl” restarts if they are manually terminated.

This is the problem we’ll look at next.

Permanent Activation

To make these changes permanent, you must modify the sysctl file so that it loads our modifications when the system boots up. Add the line: net.ipv4.ip_forward=1 at the end of the file “/etc/sysctl.conf.” This entry will be added or un-commented, as indicated:


| net.ipv4.ip_forward = 1

For example, you can use the following code for IPv6:

| net.ipv6.conf.all.forwarding=1

After you’ve finished making your changes, save them. Then use the command to reload it, which will apply the modifications right away:

| sysctl -p /etc/sysctl.conf

Enabling IP-Forwarding for IPv4 in Debian GNU/Linux

Setting up a computer network might be difficult at times. Allowing IPv4 Forwarding on a Linux machine is quite easy. The phrase IP Forwarding refers to the act of sending a network packet from one device’s network interface to another on the same device. When you want your system to function as a router that moves IP packets from one network to another, it should be enabled.

On a Linux system, the Linux kernel contains a variable named “ip_forward” that keeps this value. It may be accessed using the file `/proc/sys/net/ipv4/ip_forward`. Because a normal user who just runs a single computer without more components does not require IP Forwarding, the default value is 0.

VPNs, on the other hand, maybe classified as routers, gateways, and VPN servers. For these devices, it’s a must-have feature.

Finally, we’ll show you how to enable IP Forwarding temporarily and permanently.

IP Forwarding As A Temporary Solution

This kernel option should be enabled on the fly using one of two methods. The first method is to write the value of 1 into the variable from above like so: Option 1 simply stores the value of 1 in the variable from above as follows: # echo 1 > /proc/sys/net/ipv4/ip_forward

Option 2 employs the `sysctl` command, which allows you to change kernel parameters at any time. . As an administrator, run the following command.:

# sysctl -w net.ipv4.ip_forward=1

Please keep in mind that this setting is instantly altered. Furthermore, the result will not be preserved if the system is restarted.

You may query the value that has been previously stored:

# cat /proc/sys/net/ipv4/ip_forward

The command returns the value 0 if there is no IP Forwarding, and 1 if IP forwarding is active. Sysctl may be used to determine the current status, but there are also other methods. Alternatively, you may use sysctl to reveal the current status:

# sysctl net.ipv4.ip_forward

net.ipv4.ip_forward = 0


Enabling IP Forwarding Permanently

To do so, certain additional procedures must be completed. To begin, edit the file /etc/sysctl.conf. Remove the # at the beginning of this line: “net.ipv4.ip_forward=1”.

To enable the new settings, save the file and run the sysctl command:

# sysctl -p /etc/sysctl.conf

The option `-p` is short for `–load`, and requires a name for the configuration file to be followed.

The following command restarts the proc file system that gives information about the status of the Linux kernel:

# /etc/init.d/procps restart

The file name was shortened from “procps.sh” to “procps” in about 2015. So, instead of “procps.sh,” you must use the script on old Debian systems known as “procps.sh.”

Is Ip routing the same as IP forwarding?

Essentially, IP forwarding is a method for determining where a packet or datagram may be sent. A method is used to send a packet over several networks via a path.

What is IP forwarding in the firewall?

In networking, port forwarding is a form of network address translation (NAT) that turns a contact request from one address and port number variety to another as the packets travel via a network gateway, such as a router or firewall.

Does Docker require IP forwarding?

To function, Docker networking requires the host to be able to perform certain activities. To access the machine from external networks, you must first enable IP forwarding on your Linux host. This is something that every modern operating system has built in.


We hope you got the most out of our detailed guide on what is IP forwarding and how it works. The guide contains details regarding IP forwarding and what are the best suitable commands for it. The commands contain details regarding enabling and disabling IP forwarding in Linux operating systems.