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Does a Firewall Slow Down Internet Speed?

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How a Firewall Affects Internet Speed

Yes, a firewall will have a slight effect on internet speed if it is unable to process data as fast as your internet speed. To check, take a look at the specs of your firewall. 

For example, if you have the FortiGate 1800F next-generation firewall (NGFW), you receive complete threat protection throughput at a rate of 9.1 Gbps. If your internet service provider (ISP) gives you more than 9.1 Gbps and you have all the protection features of the 1800F turned on, your speeds will be effectively limited to 9.1 Gbps. If this affects your business’s operation, you will be better off using the 6500F, which provides 100 Gbps of threat protection, or another faster model.

The FortiGate 1800F provides very high throughput, but many firewalls do not give you threat protection this fast. If you are using any of those, you may notice a speed difference.

Understanding the Basics

How does a firewall affect internet speed? A firewall inspects packets of data before allowing them to pass through to your network, and this can affect internet speed. Because of the way a firewall works, its effect on internet speed depends on the kind you have: hardware or software. 

Here are a few things to keep in mind about a hardware vs. software firewall:

  1. A hardware firewall is a physical appliance positioned at the edge of your network or a segment of it. It affects speed as it inspects data packets, particularly if it does not come with adequate throughput.
  2. A software firewall is installed on your computer, so it can only impact the speed of that particular device, not your entire network.


A firewall takes the data packets trying to pass through it and filters out potentially harmful data. This is done using a set of rules programmed into the firewall meant to detect and discard malicious data.

Reduced Internet Speed

Can a firewall affect internet speed as it performs its duties? Yes, because it takes time to examine each data packet. If the firewall cannot do this quickly enough, you may notice a speed difference.

How To Fix Firewall Internet Speed Issues

There are a few ways to address speed issues. These steps have to be taken carefully to avoid negating the benefits of a firewall.

Test Internet Speed

First, test your internet speed. Check to see how it compares to what you are supposed to be getting from your ISP. Test it using an Ethernet cable connected directly to your modem.

Disable Firewall

If you are using both a hardware and software firewall, disable the hardware firewall first by going to its settings panel. Keep in mind that a firewall can provide web application security and prevent Structured Query Language (SQL) injection, spoofing, malware, and other kinds of attacks, so scan your computer for threats after testing.

On the other hand, if you are using your firewall to set up a virtual private network (VPN), you should turn off the software firewall first. In this way, you can maintain your VPN connection, and if the test reveals the software firewall is affecting your speed, you will have found the issue without interrupting your connectivity. You can learn more about firewalls as VPN solutions here.

How To Choose a Firewall

If you are in the market for home, enterprise, or small business firewalls, deciding how to choose one is fairly straightforward.

  1. Enterprise firewall. An enterprise firewall typically costs more but provides very high throughput—in the case of an NGFW, deep, thorough packet inspection. If you have a large network and a significant amount of data that you need to protect, go with an enterprise firewall.
  2. High-performance, smaller network firewall. The vast majority of small-and-midsize businesses (SMBs) are well-protected with a regular network firewall. The key is to choose one that provides enough threat protection throughput, as described above.
  3. Cloud firewall. A cloud firewall is a good solution to protect your web applications hosted in the cloud, as well as prevent threats that could arise due to remote employees connecting to your network through the cloud.

Do You Need Both Hardware and Software Firewalls?

If you have a high-throughput NGFW capable of performing deep packet inspection (DPI), you may not need both a hardware and software firewall. That one device could get the job done. However, it is always best to have both a hardware and software firewall because if a threat is able to bypass your hardware firewall, the software one, which is installed on your device, can potentially catch it.

How Fortinet Can Help

Fortinet offers a diverse selection of FortiGate NGFWs to provide ultra-fast security, thanks to high throughput and the incorporation of artificial intelligence and machine learning technologies to protect your network in real time.

In addition, Fortinet web application firewalls (WAFs) defend your web apps from attacks, including the OWASP Top 10, zero-day attacks, and unknown and known vulnerabilities in your applications.

With SD-WAN solutions, you can automate how traffic is processed, as well as how bandwidth is allocated to specific applications and areas of your network.


Will a firewall slow down internet speed?

Yes, particularly if it does not have enough threat protection throughput.

How does a firewall affect internet speed?

A firewall has to inspect data packets as they attempt to enter your network or device, and the inspection process takes time.

How do you fix firewall internet speed issues?

To fix internet speed issues as a result of a firewall, you should first connect to your modem directly, then check your speed after first turning off your hardware firewall and then turning off your software firewall. When you see which one is causing the speed issue, upgrade to a firewall solution that provides faster throughput.