Microsoft KB Archive/259783

= PPPoE with ICS Requires MTU Setting Below 1492 on the ICS Clients =

Q259783

Formal product support for Microsoft Windows XP will be available from Microsoft beginning October 25, 2001. Until then, you can consult with your counterparts, peers, and Microsoft Most Valuable Professionals (MVPs) by using our online newsgroups. Access to the Microsoft newsgroups is available from the following Microsoft Web site: "http://communities.microsoft.com/newsgroups/default.asp"

-

The information in this article applies to:


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional
 * Microsoft Windows 2000 Professional

-

SUMMARY
If you are using Internet Connection Sharing (ICS) and the outbound connection uses PPP over Ethernet (PPPoE), the clients that are using the ICS connection may not be able to browse some Web sites or send e-mail messages that contain attachments.

PPPoE requires lowering the Maximum Transmission Unit (MTU) setting on all client computers to a value no larger than 1,492. (The default is 1,500.) In some cases, a value less than 1,492 may be necessary.

In order to determine the proper MTU size, perform the following steps:


 * 1) Determine the default gateway of the ICS server using IPCONFIG.
 * 2) From a command prompt on a client, type PING -f -l  . Start with an MTU size of 1,454.
 * 3) If this fails with an error message indicating that it must be fragmented, decrease the MTU size and try again. Repeat this until the ping command succeeds.

MORE INFORMATION
PPPoE is a method for establishing PPP connections through Ethernet network adapters; this is described in RFC 2516 and is currently being used by DSL service providers to maintain the familiar &quot;dial-up&quot; experience when users connect to the Internet through a DSL modem. For additional information about setting the MTU value in Windows, click the article number below to view the article in the Microsoft Knowledge Base:

"Q120642 TCP/IP and NBT Configuration Parameters for Windows NT" Additional query words:

Keywords : w2000stack kbStack

Issue type : kbinfo

Technology : kbwin2000Search kbwin2000ProSearch kbwin2000Pro

Last Reviewed: October 3, 2001

-

[mailto:MSDN@MICROSOFT.COM Send feedback to Microsoft]

© 2002 Microsoft Corporation. All rights reserved.