Adjusting the MTU
MTU problems may result in degraded network service, but may not affect some users' abilities to access the required applications, so sometimes MTU problems go unreported. Other times, MTU problems cause severe lags in network logon times, cause email attachments and other functions within Outlook to fail, and cause applications to stop functioning entirely. Note that, by default, the MTU on Windows operating systems is 1500 (Ethernet) and that a change to 1492 may resolve some, but not all, problems.
You may want to use MTU DOS Ping Test to determine the optimal MTU setting. The MTU must be set to the same setting on all your PC NICs and router. When using VPN, there is additional overhead and you may need to reduce the MTU to 1400 if you experience difficulties accessing email, web, or DSL connectivity problems.
For Windows 95, 98, ME and NT 4.0 - use the Freeware GUI utility DrTCP. It is available for download at http://www.dslreports.com/front/DRTCP021.exe. Select the LAN Adapter from the Adapter Settings dropdown box. In the MTU field, type "1400", then click Save, and click Exit. Reboot the PC, and the MTU will be set to 1400. Re-try some the applications that were previously having problems.
NOTE: DO NOT USE DR. TCP ON WINDOWS 2000 & WINDOWS XP.
(top)
Windows XP MTU
The Windows built-in PPPoE client has a default MTU of 1480. To change the MTU, please refer to the Microsoft Knowledgebase: http://support.microsoft.com/default.aspx?scid=kb;en-us;283165 and http://www.microsoft.com/windowsxp/pro/using/howto/networking/pppoe.asp
Important Note: Changing the MTU in Windows XP requires use of the Registry Editor. Please heed the warning on Microsoft's site regarding use of the Editor. Expedient cannot be held responsible for any problems or damage that occurs as a result of using the Registry Editor incorrectly.
(top)
Please refer to the Microsoft article: http://support.microsoft.com/default.aspx?scid=kb;en-us;120642. Instructions for setting the MTU are roughly 1/3 the way down on this page.
Important Note: Changing the MTU in Windows 2000 requires use of the Registry Editor. Please heed the warning on Microsoft's site regarding use of the Editor. Expedient cannot be held responsible for any problems or damage that occurs as a result of using the Registry Editor incorrectly.
(top)
Macintosh OS X MTU
You can manually set the MTU value for en0 or en1 by doing "/sbin/ifconfig en0 mtu 1492" (or en1, depending on your interface). The MTU will be reset on the next reboot. See http://docs.info.apple.com/article.html?artnum=107474.
Note: If difficulties persist, try the following list of values, one value at a time, in this order, until the problem is solved: 1462, 1400. See MTU Ping Test for information on determining the optimal MTU.
(top)
Linksys Router
If you use the Linksys BESW-11S4 Wireless 4-port routers, please note that the older versions of the firmware do not include MTU settings. We recommend upgrading the firmware which will allow you to enable custom MTU sizes.
- Connect to the Router by opening a web browser and entering http://192/168.1.1 or the IP address of the Router.
- Enter the password if asked (default is "admin").
- Click Advanced and select the Filters tab.
- Look for the MTU option and select Enable. In the Size: field, enter the appropriate MTU (e.g. 1492).
- Click the Apply and Continue buttons to complete the task.
Note: If difficulties persist, change the Size: to different values. Try the following list of values, one value at a time, in this order, until the problem is solved: 1462, 1400. See MTU Ping Test for information on determining the optimal MTU.
Please note that Expedient does not provide support for the D-Link Router and that this information is provided only for your reference.
- Open a browser and type 192.168.0.1 into the Address field to access the router.
- Enter admin into the username field; leave the password field blank unless you have set a password.
- Click the WAN button. In the MTU field, enter the appropriate MTU setting. See MTU Ping Test for information on determining the optimal MTU.
- Click Apply and restart the modem.
WinPoET
When using WinPOET, the MTU registry setting is changed from the default of 1500 to 1492. After installation of WinPoET, if you have VPN, you will receive a message: "An MTU settings has been changed in your registry. In order for these changes to take affect the system must be rebooted". Restart the computer.
(top)
 |
Was this information helpful?
|
 |
 |
| |
 |
|
 |
|
Print Page |
Contact Us |
