What is the best way to set the router MTU value?

In our commonly used Windows XP operating system, the default MTU value is 1500, which is a standard Ethernet setting value that is not suitable for broadband networks, whereas the MTU of General ADSL broadband is between 1450 and 1492, The discrepancy of the MTU between the system and ISP will directly result in the data in the network transmission process of continuous subcontracting, packaging, waste valuable transmission time, but also seriously affect the efficiency of the broadband. This requires that we set the native MTU value to be the same as the MTU value used by the ISP to quickly browse the Web and download the data. However, the MTU values used by ISPs in each region are different, and the ISP changes the local MTU size irregularly, which can be a great inconvenience to setting up the native MTU, so how do we know how much the ISP's MTU is? In fact, Our most commonly used ping commands can easily help us test the local ISP's MTU size, if you are interested, please follow the author to see it.

Test ideas

On a wide area network, packets that exceed the requirements of the ISP will not be transferred, and the operating system will automatically subcontract the size of the data not in accordance with the native MTU value, so we can send a fixed-length packet to a host on the Internet. And does not allow the operating system to change its size to check whether the packet can be transmitted properly, and if the packet is less than or equal to the ISP's MTU, the transmission will work correctly, and if the packet sent is greater than the MTU value used by the ISP, the transmission fails. This allows us to eventually get the MTU size of the ISP end by sending different sizes of packets, and this data plus 28-byte header information is the final MTU value we need.

Test steps

1. dial-up Internet access, and open the "Start" menu → "program → attachment → command Prompt"

2. Enter the command "Ping–l 14xx–f www.45it.com", here we explain the meaning of the command parameters

*–l 14xx parameter: Send a fixed-length packet, 14xx is to test the packet size, as mentioned above, ADSL MTU generally between 1450 and 1492, the 3rd step will be replaced each time the value

*–f parameter: Notifies the operating system that the packet size cannot be changed privately

* Www.45it.com: Any host on the Internet, other host names or IP addresses can also be used

3. Observe the results of the feedback and determine the ISP's MTU value (please note the picture of the Yellow box section)

1 The first time to send test kits, packet length 1450

As shown in Figure 1, the packet is too large to be wrapped, so it is judged that the value (1450) is greater than the ISP's MTU and should be reduced in size

2 The second time to send test kits, packet length 1440

As shown in Figure 2, the packet size drops to 1440, prompting that the packet should be too large, so that the value (1440) is still greater than the ISP's MTU and should continue to decrease

3 The third time to send test kits, packet length 1430

As shown in Figure 3, the packet size drops to 1430, prompting the packet to be transmitted normally, thus determining the ISP's MTU value between 1440~1430

4 The fourth time to send the test package, packet length 1435

As shown in Figure 4, the packet size rises to 1435, the hint is still normal to transmit, so the MTU value is judged between 1440~1435

5 The fifth time to send the test package, packet length 1438

As shown in Figure 5, the packet size rises to 1438, prompting for normal transmission, so the MTU value is judged between 1440~1438

6 The packet length of 1439 packets sent six times

As shown in Figure 6, the packet size rose to 1439, indicating that the packet was too large to transmit, so the ISP's MTU value was determined to be 1438

4. Calculate the MTU value of the local computer

The MTU value obtained above cannot be used directly on local settings and should be added with 28 (header size), so the final MTU value is 1466

5. Modify the native MTU value

Modifying the local default MTU value can be done through the registry, but the more intuitive approach is to use some system optimization software, such as "Super Bunny" or "Master of Windows Optimizer", and so on, this example uses "Super Bunny V6.25" to demonstrate. Figure 7 is the screen to enter the Magic Settings Network Settings tab, first check the "Use Maximum transmission unit" before the tick, and then enter the calculated MTU value (1466) from the subsequent data bar, then click OK and restart the computer.

Summarize

As mentioned above, the whole process may seem cumbersome, but the idea is very simple, and the effect is good. The author's computer set the MTU value, the browser to open the page speed is not set up before the increase of 15%, the effect is very obvious. ㄖ Huang Bi ppoe dial-up ADSL, for optical access or ISDN access broadband network is not applicable to this method.