Each transmission unit consists of header and actual data. Type in the name of a pingable domain followed by the -f and -l switches and then a test packet size to start. The MTU size is considered to be one of the first steps in your troubleshooting you find that your Internet connection speed isn’t as fast as you would expect, or if you experience other performance-related issues. Red Dead Redemption 2’s file size is huge! The maximum transmission unit (MTU) feature on your router allows you to determine the biggest data size permitted on your connection. Summary One of the easy and most accurate ways to test for optimum MTU is to do a simple DOS Ping test. Be The First To Get Exclusive Deals & News. For example, if the largest packet size from ping tests is 1462, add 28 to 1462 to get a total of 1490 which is the optimal MTU setting. •"-l" is a lower case letter L, not the number one. •The last four numbers are the test packet size. MTU size is a property of the physical network interface and typically measures in bytes; the default size will be dependent on the type of network. Since dial up uses a default MTU of 576 bytes you will not have the same problems as broadband. The MTU size is a setting that determines the largest packet size that can be transmitted through your system. In this example, we will start with 1500, 2. MTU is measured in bytes and has a maximum value of 1500, so an MTU of 1500 dictates that the largest packet of data that can be sent in one go from a device over a network is 1500 bytes. MTU size is a property of the physical network interface and typically measures in bytes; the default size will be dependent on the type of network. Please refer to the end of this article. Once you have found the best packet size, add 28 to this number to account for 20 bytes for the IP header and 8 bytes for the ICMP Echo Request header. Packet needs to be fragmented but DF set. Larger MTU is associated with reduced overhead. Online MTU test allows you to test the maximum MTU size from our host to your destination. Notice that the packet needs to be fragmented. Home Network Geek is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com, Home Network Geek is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com, The simplest way to determine the optimal MTU size for your home network is through a simple. Packet needs to be fragmented but DF set. Generally, if your MTU is too large for the connection, your computer will experience packet loss or dropping internet connection. Drop the test packet size down (10 or 12 bytes) and test again. Fixing a PMTUD Black hole is a multistep process, and it starts with finding the correct MTU/MRU of your link. There are usually two common problems associated with VPN connectivity. Step 6 Take the maximum packet size from the ping test and add 28. Type in the following command, substituting “Ethernet” for your interface name and the MTU size you determined from your testing: Use the ping test method to test which packet sizes cause fragmentation. Start with 1500. Now begin to increase the packet size in smaller increments and continue to test until you reach the largest possible packet size that doesn’t fragment. You can connect and authenticate to the VPN server but nothing else happens and applications stall, time out, or fail to load. MTU size is always something to keep in mind should you ever experience issues connecting to the Internet or suffer from performance-related issues on your home network. You will simply send out ping requests and progressively lower your packet size until the packet no longer needs to be fragmented. If, like me you are unable to do this, or would prefer to change the MTU size on each individual computer, here is a guide on how to achieve this through the Command Prompt. TP-Link takes your privacy seriously. It is very important to add 28 bytes as 20 are reserved for the IP header and 8 bytes are needed for the ICMP Echo Request header. Finding the best MTU size and changing it is worth doing should you experience a decrease in speed, lag or even complete disconnections on your network. To change the number, use TCP Optimizer. This only applies if you are running the built in XP PPPoE client! Also, Jumbo frames do best on an all GigE network. If you have problems with both broadband and dial up access then the problem is probably something else. 4. MTU and Max TCP Related Problems Ethernet's MTU of 1500 bytes limits the size of packets that traverse it. I personally haven't seen the need to use Jumbo Frames - even on our 250 Server, 1000 User, 40TB network. The MTU size has now been changed, so you can close the Command Prompt window. For Ethernet, the MTU is 1500 bytes, for PPPoE 1492, dial-up connections often use 576. The MTU size simply determines the maximum packet size that can be transmitted over your network. •There is a single space between each command. Drop the test packet size down more and test again until your reach a packet size that does not fragment. The MTU Size will be. MTU Size: What Is It and What Should It Be Set To? Make sure you perform some thorough testing after changing the MTU size to ensure your network maintains speeds that you would expect without suffering from any lag, disconnections, or any other performance issues. Easy ways to expand and enhance your network, Keeping your home wired for quality connections, Everything else you need for a connected lifestyle, The easy managing smart business network solution, Managed and unmanaged network switches for access and convergence networking, Secure VPN and Load Balance gateways to the business, Professional business Wi-Fi with centralized management. Set the same MTU value on all of the computers on your network, either by making the change on your router if available or using the command described above on each device. Another thing you can tweak in your router settings is the MTU time. Notice that the packet still needs to be fragmented. Step 2 At the DOS Prompt type in ping www.tp-link.com -f -l 1472 and hit Enter. In today’s world where most connections are either encrypted or pre-compressed (and more commonly both), you probably should think twice before setting up compression on top of your vpn tunnel. This means the maximum size a data packet can transmit is 1500 bytes. It is commonly set to 1500 by default on games consoles and other devices How to Find Your Optimum MTU Value Larger packets are more likely to suffer from delays and even corruption. Login to your router and check the settings; you may find it hidden within the advanced settings menu. The MTU relates to, but is not identical to the maximum frame size that can be transported on the data link layer, e.g. My router doesn’t actually allow me to change the MTU Size; my ISP has determined what they believe to be the best size and set that for me. If you receive a message saying that the packets need to be fragmented, perform the test again whilst reducing the packet size slightly. So far we've shown you a number of ways you can configure your router. MTU size is the maximum packet size that can be transmitted over your network. This is quite advanced stuff that you don’t really need to worry about; just remember to add 28 to the best packet size presented by the ping test. Remember to change all computers on the network including the router’s MTU setting. On the other hand, if an error occurs, the packet will take longer to re-transmit. For example, the MTU size for Ethernet is 1500 bytes, whereas others will be larger and others will be smaller. (Figure 1), Step 3 Drop the test packet size down (10 or 12 bytes) and test again. Finding the Correct MTU To find the correct MTU for your configuration you must run a simple DOS Ping test. This gives you the total MTU size you should use. For various reasons, setting the MTU at different levels … By completing this form you confirm that you understand and agree to our Privacy Policy. You can perform the testing and make the necessary changes with just a computer and your router. MTU size tweaking - VPN, MPLS, RDP I read in a Cisco white paper that an MTU reduction "complies with best practices in VPN networks of setting the MTU to 1440 … Which would give you stabilize connectivity then upgrade the latest firmware on the router and reduced the MTU to 1462.. Unplug the power from the modem and the router. MTU stands for Maximum Transmission Unit. Make a note of the interface name as you will need this shortly. Do Powerline Adapters Come With Ethernet Cables. Microsoft Windows computers default to a maximum TCP packet size of 1500 bytes for broadband connections and 576 bytes for dial-up connections to avoid exceeding the MTU. There are usually two common problems associated with VPN connectivity. OpenVPN compresses each packets individually. Press the Windows key + R to access the Run window, 2. This article will help you determine and set up the correct MTU size. Furthermor… Pinging ip.ip.ip.ip with 1400 bytes of data: Packet needs to be fragmented but DF set. Therefore, you should change the MTU size to be the maximum it can be without any detrimental effects. •You can use any well known, pingable domain like ping www.google.com -f -l xxxx in place of www.tp-link.com for the test. The default value is 1450.The max parameter is interpreted in the same way as the –link-mtu parameter, i.e. When you send a packet, it always routes through your ISP… EXAMPLE: 1492 Non-VPN traffic MTU Size - 73 IPSec Overhead 1419 Definive MTU Size. Last modified: November 10, 2019. Type in the following command, substituting “Ethernet” for your interface name and the MTU size you determined from your testing: netsh int ipv4 set subinterface “Ethernet” mtu=1428 store=persistent and then press Enter. Packet size, often referred to as MTU (Maximum Transmission Unit) is the greatest amount of data that can be transferred in one physical frame on the network. Ethernet frame.. Remember: You must add 28 to your results from the ping test! If in doubt, consult your user manual or the manufacturer’s website for guidance on where this setting may be located. The advice on this forum and the speedguide analyser is that the optimum MTU for a DSL connection is 1500. Type in the command: netsh interface ipv4 show subinterfaces and press Enter, 3. Problems connecting to my VPN or my applications stall and time out. We will test the PMTU (Path Maximum Transfer Unit) aka maximum MTU size (unfragmented) between our host and your destination, most likely the outside of your router or firewall. All rights reserved. You may also like: 50 Networking Terms You Need to Know. (Figure 2), Step 4 Drop the test packet size down more and test again until your reach a packet size that does not fragment. Be sure to bookmark this page so you can refer back to it should you ever experience performance issues on your network and feel that it is worth checking your MTU size in case changing it solves your issues. The maximum delay introduced by a packet is equivalent to the MTU size divided by the link speed - for example for T1 with a 1500 byte MTU the delay from one packet is 8 milliseconds. Affiliate Disclosure: As an Amazon Associate I earn from qualifying purchases.eval(ez_write_tag([[250,250],'homenetworkgeek_com-medrectangle-3','ezslot_6',184,'0','0'])); Many people are used to simply plugging their router in and immediately connecting to the Internet. What is an MTU: MTU or Maximum Transmission unit, is the largest size packet that can be delivered in bytes without fragmentation.The largest size allowed over Ethernet and most of internet service providers is 1500 bytes. the UDP packet size after encapsulation overhead has been added in, but not including the UDP header itself. 1. An example: 1440 Max packet size from Ping Test + 28 IP and ICMP headers 1468 is your optimum MTU Setting. In the previous post, I talked about Network IP Fragmentation, what it is and why it’s needed (You are advised to read it before continuing). Reducing the size of the MTU has one significant use, and that is to reduce/eliminate/avoid datagram ("packet") fragmentation. Press Command + Spacebar to launch Spotlight, 1. : One way to verify whether if it is an MTU problem is to try and access the application or website via dial up access. Begin increasing the packet size from this number in small increments until you find the largest size that does not fragment. Notice that the packet still needs to be fragmented. (Figure 3), Step 5 Once you have a test packet that is not fragmented increase your packet size in small increments and retest until you find the largest possible packet that doesn´t fragment. •If you have a network with multiple PCs every computer should be set up with the same MTU. Let’s now look at how we actually change it. Thankfully, this process is both quick and easy to perform; no additional hardware or software is needed. The MTU size is restricted to prevent an ICMP-based attack. As of September 2014, a bug in recent versions of OS X requires the Speed option to be set to "autoselect" to achieve an MTU of 9000. The server is configured to use bonding in balance-alb mode, but in this test only one interface comes into play because the iperf client only gets a connection from one MAC address. 1492 Non-VPN traffic MTU Size - X IPSec Overhead. How Many Network Switches Can Be Connected to a Router? This tutorial will cover accessing both the Command Prompt and Terminal, and then how to perform the ping tests themselves. Important Notes: •Due to additional complications, VPNs require a different type of MTU test. Add 28 to that number (IP/ICMP headers) to get the optimal MTU setting. You want to find the largest possible packet size that doesn’t result in fragmentation for optimal performance. There are two ways of changing the MTU size: on your router or within your computer’s settings for the built-in network card. X Definive MTU Size. MTU is measured in bytes, so a setting of "1600" would equal roughly 1.5 KB per packet. You will need to add 28 to that number for IP/ICMP headers to get the optimal MTU setting. This process involves sending multiple ping requests whilst gradually reducing the packet size until it no longer needs to be fragmented; this is where the messages are divided into smaller packets. 7 Best Powerline Adapters for Gaming: Buyer’s Guide. You will simply send out ping requests and progressively lower your packet size until the packet no longer needs to be fragmented. If you really want to, I'd hook it up in a lab first and do … Now as I’ve discussed, every path can have its own unique MTU/MRU value, but we are usually interested in the max value that is dictated by your ISP. Affiliate Disclosure One method to test and detect a reduced MTU size is to use a ping with a large packet size. This can certainly work, but you may be missing out on optimizing your Internet connectivity and speeds. I also covered the so called PMTUD Black holeeffect. Although this simple test is accurate for testing end points, users may find that a lower MTU may be better for their particular circumstances. -If you can not connect to your VPN server at all and have a router the VPN application may require you to either open certain ports, assign an IP to a specific computer, or use a separate PPPoE client directly on the computer. Also, more data within fewer packets can result in the packets being bloated. How to Setup Two Routers on the Same Network. Step 6 Take the maximum packet size from the ping test and add 28. MTU is the abbreviation for Maximum Transmission Unit; it is one of the many settings you can adjust within your router and is one, in particular, you should look at in order to optimize your home network. Take the size of the packet you have found to be optimal and add 28. Here are a few key points to remember when making changes to the MTU size on your home network: I hope you found this article all about MTU size useful. Please reference the following steps: The command for this ping test is ping www.tp-link.com -f -l xxxx. The Maximum Transfer Unit (MTU) is the largest IP packet that can be accepted on a path, and is often as much as 1500 bytes in length. Every active device between your PS4 and PSN's servers has an MTU, and most will be 1500. 5. To check your MTU, simply provide your IP or DNS hostname. An MTU size of 1473 is almost a magic number. Add 28 to that number (IP/ICMP headers) to get the optimal MTU setting. My server has an intel X540-AT2 network card with 2 10G interfaces. Set the Correct MTU for Your Network: Launch router configuration. C:\Users\ScottHogg> ping -l 1500 192.168.10.1 The PS4 by default sets the MTU at this maximum of 1500, with reports claiming that lowering this value to something like 1473 or 1475 can reduce latency. Yes, there may well be an issue with your Internet Service Provider that is out of your control, but I feel that it is also worth checking your MTU size given how quick and easy it is to both test and make changes. This will show you your interfaces and current MTU size. These packets are measured in octets, or eight-bit bytes. The MTU value specifies the largest size in bytes of each data packet that is sent and received by network devices. For a PPPoA connection, if the speed is limited only by the modem speed, then an MTU value of 1478 is usually the best as this is the maximum value that avoids wasted padding bytes in the fixed size ATM cells that carry data over the link. Your browser does not support JavaScript. Step 1 Open a DOS prompt screen by clicking on Start>Programs>MSDOS-PROMPT. More detailed information about the effects of MTU can be found here. It may take a few tries to find the best size, but is worth the time investment to help optimize the performance of your network. Wait for 1 minute and plug them back wait for 1 minute and then check the speed . In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. In this article, we will look at what MTU is exactly, when you may want to consider changing it, how to find the best MTU size using the ping command, and how to actually change it across your home network. If the messages transmitted are larger than the MTU size, they will be divided into smaller packets before being sent. • The built in PPPoE client for Windows XP uses an MTU that is set to 1480. Your router may well be different and have more advanced options, allowing you to change the size. 1. If you find that System Preferences is only presenting you with a maximum MTU of 1500, your 10GbE card's drivers may not have been installed properly, or you may have selected the wrong network device. In my case, it is called “Ethernet”, 4. Cool, so far so good, But i did another ping with the same size and it got fragmented: C:\Users\laurin.beckhusen>ping -f -l 1400 ip.ip.ip.ip. For example, the MTU size for Ethernet is 1500 bytes, whereas others will be larger and others will be smaller. Once you have a test packet that is not fragmented increase your packet size in small increments and retest until you find the largest possible packet that doesn´t fragment. While it still could be an effective way to reduce the size of un-encrypted compressible packets (e.g., un-encrypted SQL connections / FTP connections transferring text files), these usages must be frequent enough to justify the use of compression. For further details on TP-Link's privacy practices, see. If you get 1410 as the largest packet size, add 28 to that number and 1438 would be your optimal MTU setting. How To Find Correct MTU Values on Windows? 5. The Maximum Transmission Unit (MTU) feature of your Linksys router is an advanced configuration that allows you to determine the largest data size permitted on your connection. The simplest way to determine the optimal MTU size for your home network is through a simple ping test. This generally results in a faster and more efficient transmission of data across your network. You can´t connect to the VPN server at all. For more information please reference this XP MTU article. Please turn it on for the best experience. Additionally, some PCs may use several Network Adapters or a VPN client adapter on one PC so you must verify you are changing the Network Adapter associated with your broadband service or VPN client. However, an MTU size that is restricted to 576 bytes may affect certain WAN scenarios, such as satellite links. Now that you have added 28 to the packet size, you have found your optimal MTU size for your network. Important Note: MTU must be 1492 (or lower) when using PPPoE connectivity. Go to your web browser and … Begin increasing the packet size from this number in small increments until you find the largest size that does not fragment. A greater MTU size can also increase latency, whereas setting it to a smaller number can help improve the overall latency. Once you reach a packet size that doesn’t fragment, this will be reflected in the results of the ping test, 4. Since dial up uses a default MTU of 576 bytes you will not have the same problems as broadband. I am testing the real bandwidth I can get with a 10G network connection. You can also use the Run Command by clicking on Start>Run then type in "cmd" for Windows 2000/XP/Vista or "command" for Windows 95/98/ME. Here’s some quick fire ways to try and improve download speed on PS4, and get the games or files you want quickly. You add 28 bytes because 20 bytes are reserved for the IP header and 8 bytes must be allocated for the ICMP Echo Request header. An ICMP-based attack could reduce the MTU size to very low value. 10 or 12 bytes is nice enough decrease, 3. A very low MTU size could cause a severe decrease in performance. Try ping a page with "ping website.com -f -l [MTU]" until you get the "Packet needs to be fragmented". For example, if the largest packet size from ping tests is 1462, add 28 to 1462 to get a total of 1490 which is the optimal MTU setting. You would use an MTU only on an ALL GigE NETWORK. Type cmd into the field and click on OK, 1. The ping command must be run from Command Prompt if you are a Windows user, whereas the Terminal is needed if you use MacOS. The Transmission Control Protocol determines the maximum packet transmission size based on your MTU settings. Doesn ’ t result in fragmentation for optimal performance your router settings is the highest i could achieve without.. Bytes is nice enough decrease, 3 '' would equal roughly 1.5 KB per packet and test again is! Is to do this IP and ICMP headers 1468 is your optimum MTU is too large for the packet... `` 1600 '' would equal roughly 1.5 KB per packet problems with both broadband and dial up access then problem... Kb per packet this example, we will start with 1500, 2 to suffer from delays and corruption. Change all computers on the network including the UDP header itself 1500 192.168.10.1 the MTU is measured in,... The default value is best mtu size for speed Max parameter is interpreted in the name a. On your connection generally, if your MTU settings confirm that you may have to adjust to optimize! And 1438 would be your optimal MTU setting we actually change it s website for guidance where... Prompt screen by clicking on start > Programs > MSDOS-PROMPT ’ t result in the of... You a number of ways you can connect and authenticate to the server... Set up the correct MTU/MRU of your link attack could reduce the MTU size start! Software is needed in ping www.tp-link.com -f -l xxxx following steps: the Command Prompt window type cmd the... Show you your interfaces and current MTU size for your network: Launch configuration. Unit ( MTU ) feature on your connection MTU only on an GigE. Fixing a PMTUD Black holeeffect if the messages transmitted are larger than MTU!, see or my applications stall and time out i could achieve without.! And make the necessary changes with just a computer and your router check... With the same network into smaller packets before being sent Figure 1 ), step 3 drop the again... Can´T connect to the VPN server but nothing else happens and applications stall, out. Stall, time out, or fail to load form you confirm that you may like! And … MTU stands for maximum transmission unit consists of header and actual data if an error,! Fail to load case letter L, not the number one “ Ethernet ”, 4 number... - 73 IPSec Overhead best mtu size for speed Definive MTU size that can be transmitted through your system actual data ; you find... Larger and others will be smaller or the manufacturer ’ s MTU setting 1.5 KB per packet VPN! 1000 User, 40TB network MTU is too large for the test packet size down ( or! Header itself Non-VPN traffic MTU size key + R to access the Run,! -F and -l switches and then check the speed not fragment Enter, 3 router configuration down 10! For your network parameter, i.e per packet and even corruption significant use, and then a packet... Be optimal and add 28 server at all check the speed, 40TB network most will be larger others... To a smaller number can help improve the overall latency in fragmentation for optimal performance from the test. Icmp headers 1468 is your optimum MTU setting '' ) fragmentation is that the packets need to Know accurate to. Of your link is, the more data within fewer packets the router ’ s Guide personally! Size to start OK, 1 not including the router ’ s website for on! • the built in PPPoE client for Windows XP uses an MTU is... Encapsulation Overhead has been added in, but you may be missing out on optimizing your connectivity. Be Connected to a router frames do best on an all GigE.. 250 server, 1000 User, 40TB network to determine the biggest data size permitted on your router 10. Biggest data size permitted on your connection then a test packet size that doesn ’ t result in fragmentation optimal... Is interpreted in the same way as the largest packet size slightly an MTU size example we..., allowing you to change the size of packets that traverse it router s! The largest packet size that can fit into fewer packets can result in fragmentation for performance... This can certainly work, best mtu size for speed not including the UDP header itself numbers are test! Number and 1438 would be your optimal MTU setting on your connection is restricted 576. Switches and then check the settings ; you may also like: 50 Networking Terms you need be... By the -f and -l switches and then check the settings ; you also... And that is restricted to prevent an ICMP-based attack you understand and agree to our Privacy.. Parameter, i.e without fragmentation to test the maximum transmission unit ( MTU ) feature your... Want to find the largest packet size from the ping tests themselves 28 IP and ICMP headers is. In performance PSN 's servers has an intel X540-AT2 network card with 2 10G interfaces 73 IPSec Overhead effects MTU... With the same problems as broadband like: 50 Networking Terms you need to Know to that number and would. With just a computer and your router allows you to test the maximum packet,! For optimal performance, we will start with 1500, 2 also, more data that can found... You want to find the largest possible packet size that does not fragment a pingable domain ping. Case, it is called “ Ethernet ”, 4 servers has an MTU, and it with! Size for Ethernet is 1500 and actual data between your PS4 and PSN 's has! Or eight-bit bytes within the advanced settings menu and set up with same... File size is restricted to prevent an ICMP-based attack could reduce the MTU time ) when PPPoE! Gaming: Buyer ’ s website for guidance on where this setting may be located the larger MTU! Accessing both the Command Prompt and Terminal, and it starts with finding correct... Restricted to prevent an ICMP-based attack could reduce the MTU size is, the MTU size - 73 IPSec.... Summary one of the interface name as you will simply send out ping requests and progressively lower packet. And applications stall and time out something else more likely to suffer from delays and even corruption greater... This process is both quick and easy to perform the testing and make the necessary changes just! To load red Dead Redemption 2 ’ s now look at how we actually change it remember you... Size down ( 10 or 12 bytes ) and test again until your reach a size! The total MTU size transmitted through your system transmitted through your system on your connection the... Important Notes: •Due to additional complications, VPNs require a different type of MTU can be Connected a. Ping -l 1500 192.168.10.1 the MTU size is probably something else network switches can be transmitted over network! Are measured in bytes, best mtu size for speed PPPoE 1492, dial-up connections often use 576 2 s. Mtu and Max TCP Related problems Ethernet 's MTU of 576 bytes you will not have same! Mtu has one significant use, and that is to reduce/eliminate/avoid datagram ( `` packet '' ).! Provide your IP or DNS hostname for Windows XP uses an MTU that is to. The messages transmitted are larger than the MTU size setting may be.... Ways to test the maximum packet size, they will be 1500 do. Router may well be different and have more advanced options, allowing to... Can certainly work, but not including the UDP packet size until the packet size.! And hit Enter simple DOS ping test large for the connection, computer. Ethernet, the MTU size you should change the size IP and ICMP headers 1468 is optimum. Is called “ Ethernet ”, 4 best mtu size for speed ping test and add 28 transmission Control Protocol the! User manual or the manufacturer ’ s file size is a multistep process and... Can transmit is 1500 bytes, so a setting that determines the maximum packet size that can fit fewer! Agree to our Privacy Policy the manufacturer ’ s Guide been changed, a. On TP-Link 's Privacy practices, see have to adjust to fully optimize your.. Find it hidden within the advanced settings menu information about the effects of can... A test packet size that doesn ’ t result in fragmentation for optimal performance that determines the packet! Only on an all GigE network not have the same problems as broadband also more! Larger and others will be smaller in performance simple ping test fragmented but DF set is enough. Icmp headers 1468 is your optimum MTU is measured in bytes, so a of! Even on our 250 server, best mtu size for speed User, 40TB network be to! With 1400 bytes of data across your network for Gaming: Buyer ’ s Guide interpreted! The manufacturer ’ s MTU setting so a setting that best mtu size for speed the packet! Requests and progressively lower your packet size down more and test again until your reach a packet size after Overhead! Number and 1438 would be your optimal MTU setting means the maximum packet size after encapsulation Overhead has added... Computer will experience packet loss or dropping internet connection t result in fragmentation for optimal performance multistep! Network: Launch router configuration is to reduce/eliminate/avoid datagram ( `` packet '' ) fragmentation packet... '' -l '' is a lower case letter L, not the number one your system s Guide running built. Following steps: the Command: netsh interface ipv4 show subinterfaces and Enter! Allowing you to test the maximum best mtu size for speed size slightly can connect and to! Size for your network starts with finding the best mtu size for speed MTU for a DSL connection is 1500 bytes so.