How to Make Your VPN Faster with Two Simple Network Settings?

TL;DR:

VPN slowdowns often happen because of packet fragmentation, not the VPN itself. Two network settings control this: MTU (Maximum Transmission Unit) and MSS (Maximum Segment Size). Adjusting these prevents your data from being split and reassembled, which speeds up your connection noticeably.

The Fast Fix:

• Test your network capacity using a simple ping command (takes 5 minutes)
• Calculate your optimal MTU by subtracting VPN overhead (60 bytes for most VPNs) from your network maximum
• For standard 1500-byte networks: Use MTU 1440 for OpenVPN, MTU 1420 for WireGuard
• Edit your VPN config file with the new MTU value and reconnect
• Conservative safe option that works everywhere: MTU 1380

Expected Results: Faster page loads, less video buffering, steadier download speeds, better gaming response times, and smoother video calls without changing your VPN’s security or encryption.

Why Your VPN Slows Down Your Connection

When you connect to a VPN, your data gets wrapped in extra layers of security. Think of it like putting a letter inside an envelope, then putting that envelope inside another envelope. Each layer adds protection, but it also adds bulk.

Your network equipment has limits on how much data it can handle in one chunk. When your VPN-wrapped data exceeds these limits, it gets split into smaller pieces. Your computer then has to reassemble these pieces on the other end. This splitting and reassembling process creates delays that slow down your connection.

The two settings that control this are called MTU and MSS. MTU stands for Maximum Transmission Unit, which sets the largest data chunk your network can handle. MSS stands for Maximum Segment Size, which specifically controls the data portion without counting the wrapper layers.

Finding Your Network’s Sweet Spot

Before you change any settings, you need to know what your network can actually handle. This takes about five minutes and uses a simple test.

Testing Your Network Capacity

You can test your network using a ping command. This sends small test packets to see what size works without problems.

For Windows users: Open Command Prompt and type:

ping -f -l 1472 8.8.8.8

For Mac or Linux users: Open Terminal and type:

ping -D -s 1472 8.8.8.8

This tests whether your network can handle 1472 bytes of data. The number 8.8.8.8 is Google’s DNS server, which reliably responds to these tests.

If the test succeeds, you see normal ping results. If it fails, you’ll see an error message saying the packet needs to be fragmented.

Narrowing Down the Right Size

Start with 1472 and work your way down if needed:

1. Try 1472 first
2. If it fails, try 1400
3. If that fails, try 1372
4. Keep reducing by small amounts until it works

Once you find the highest number that works, add 28 to it. This accounts for the basic internet headers that wrap around your data. The result is your network’s maximum capacity without a VPN.

For example, if 1464 is your highest working number, your network can handle 1492 bytes total (1464 + 28 = 1492).

Calculating Your VPN Settings

Now you need to subtract the extra bulk your VPN adds. Different VPN types add different amounts of overhead.

VPN Overhead by Type

开放VPN typically adds 60 bytes of extra data. 线卫 adds between 28 and 80 bytes, though most connections use around 60 bytes too.

Take your network maximum and subtract the VPN overhead:

Example with OpenVPN:

• Network maximum: 1500 bytes
• OpenVPN overhead: 60 bytes
• VPN MTU setting: 1440 bytes

Example with WireGuard:

• Network maximum: 1500 bytes
• WireGuard overhead: 60 bytes
• VPN MTU setting: 1440 bytes

Your MSS setting should be 40 bytes less than your MTU. This accounts for the basic internet and connection headers. So if your MTU is 1440, set your MSS to 1400.

Quick Reference Numbers

Most home internet connections max out at 1500 bytes. If that’s your situation, these settings work well as starting points:

• OpenVPN: Try MTU 1400 or 1420
• 线卫： Try MTU 1420
• Conservative option: MTU 1380 (works almost everywhere)

If you use PPPoE internet (common with DSL), your maximum is probably 1492 instead of 1500. Subtract 60 from that, and you get 1432 as your ideal VPN MTU.

For those interested in choosing the best VPN protocol for specific needs, understanding these settings becomes even more important.

Applying Your New Settings

The way you change these settings depends on what VPN software you use.

For OpenVPN Users

Look for your OpenVPN configuration file. It usually ends in .ovpn. Open it with a text editor and add this line:

tun-mtu 1400

Change 1400 to whatever number you calculated. You can also use mssfix, which automatically adjusts your MSS:

mssfix 1360

Save the file and reconnect to your VPN.

For WireGuard Users

Find your WireGuard configuration file (ends in .conf). Look for the section marked [Interface]. Add this line under that section:

MTU = 1420

Again, use your calculated number instead of 1420. Save and reconnect.

For Router-Level VPNs

If you run your VPN through a router like pfSense or OpenWrt, look for MSS Clamping settings. This feature automatically adjusts the packet sizes for all traffic going through your VPN.

MSS Clamping is actually the most reliable method because it happens at the router level and affects all your devices automatically. Learn more about advanced VPN features like split tunneling that work alongside these optimization techniques.

Testing and Fine-Tuning

After applying your settings, test your VPN speed using a speed test website. Compare it to your speed before the changes. You can also verify your VPN is working correctly with these optimization settings in place.

If you don’t see improvement, try reducing your MTU by 10 or 20 bytes. Sometimes networks have hidden overhead that the initial test didn’t catch.

If you’re not sure what overhead your VPN uses, start with a conservative number like 1380. This works for almost all VPN types and network conditions. You can always increase it later if your connection remains stable.

Signs Your Settings Are Working

You’ll notice several improvements when you get the settings right:

• Web pages load faster
• Video streaming has less buffering
• Downloads maintain steadier speeds
• Online gaming feels more responsive (especially important for reducing lag spikes while gaming)
• Video calls have fewer disruptions

When to Adjust Again

Your ideal settings can change if you switch networks. The MTU at your home might differ from the MTU at a coffee shop or hotel. Some VPN apps let you set different configurations for different networks.

If you notice your VPN slowing down after it was working well, your internet provider might have changed something. Run the ping test again to check if your network maximum has changed.

Real-World Examples

Understanding how this works in practice helps you apply it to your situation.

Home Cable Internet

Most cable internet connections support the full 1500 bytes. With a 60-byte VPN overhead, you’d set your MTU to 1440. 

Your connection should feel almost as fast as it does without the VPN. This optimization is particularly beneficial when accessing streaming sites through your VPN.

DSL with PPPoE

DSL connections using PPPoE typically max out at 1492 bytes. After subtracting VPN overhead, you’d use 1432. This small difference matters because your data fits perfectly without getting split up.

Mobile Hotspot

Mobile networks can have varying MTU values. Starting with a conservative 1380 or even 1280 often works better because mobile networks have more variable conditions. 

Gamers using mobile hotspots should also consider choosing the right VPN protocol for gaming performance.

Public WiFi

Public networks might have lower MTU values due to how they’re configured. Using 1380 gives you a buffer that works reliably across most public networks. Remember to always use a VPN on public WiFi for both speed optimization and security.

Common Questions About VPN Speed

Advanced Optimization Tips

Once you have the basics working, you can fine-tune further. 

For a comprehensive approach, explore these 14 VPN speed optimization techniques that complement MTU/MSS adjustments.

Test Different Times of Day

Your optimal settings might perform differently during peak internet usage hours. If you notice slowdowns during evenings, try reducing your MTU by another 20 bytes.

Consider IPv6

Some networks use IPv6, which has a minimum MTU of 1280 bytes. Using 1280 as your VPN MTU ensures compatibility across both IPv4 and IPv6 networks.

Monitor Your Connection

Keep track of your speeds over time. If you notice gradual slowdowns, it might be time to test and adjust again.

Multiple VPN Configurations

Create different configuration files for different networks. Name them clearly (like home.conf and mobile.conf) so you can switch easily.

Taking Action

Improving your VPN speed doesn’t require technical expertise. The process takes about 15 minutes from start to finish:

1. Run the ping test to find your network maximum
2. Calculate your VPN MTU by subtracting overhead
3. Edit your VPN configuration file (need help? Check this complete VPN setup guide)
4. Reconnect and test your speed

Start with the recommended numbers for your VPN type. If those work well, you’re done. If not, adjust by small amounts until you find what works best. Gamers should also explore strategies for achieving low ping and better performance.

Your VPN protects your privacy and security. These simple adjustments make sure you don’t sacrifice speed for that protection. A properly configured VPN should feel fast and responsive while keeping your data safe. 

Understanding how VPNs work for security helps you appreciate why these optimizations matter. The next time your VPN feels sluggish, remember that two simple numbers might be all you need to fix it.