This article describes how to diagnose Maximum Transmission Unit (MTU) problems.

Back to the top

With the most recent release of the Dashboard, Xbox Live users can analyze router problems on a more detailed level than they could in previous releases. Through the Dashboard’s Connect Status screen (Network Troubleshooter), you can access a new tool named the Diagnostic Server. The Diagnostic Server performs various tests to determine whether your router:

•	Has an MTU setting that is incompatible with Xbox Live.
•	Handles ICMP port-unreachable packets incorrectly.
•	Is a highly aggressive NAT-type router.

Back to the top

How the MTU setting can prevent you from connecting to Xbox Live

Your router’s MTU (Maximum Transmission Unit) setting must be higher than 1365. If it is not, you cannot connect to Xbox Live.

Back to the top

How to determine if your connection problem is an MTU router problem

To verify whether your router’s MTU setting meets the minimum requirement for Xbox Live:

1.	Select the Y button on the Connect Status screen, and then press the A button to continue to the diagnostic read-outs.
2.	You receive the following information in the Diagnostic Server window: <Version #> MT: x (aaaa – bbbb) x=0  MTU test failed and there is an MTU problem. x=1  No MTU problem. (aaaa-bbbb) is the error code
3.	If the MT shows a “1,” the router passed the test, and the MTU setting is not an issue for your router. If the MT shows a “0,” the test failed. If this is the case, you have a router that is not compatible with Xbox Live. You may have to manually change your router’s MTU setting, update its firmware, or obtain one of the routers listed on one of the following Xbox Router Compatibility Web sites: United States: http://support.xbox.com/support/en/us/xbox/xboxlive/getconnected/compatiblenetworkequipment/compatiblenetworkingequipment.aspx (http://support.xbox.com/support/en/us/xbox/xboxlive/getconnected/compatiblenetworkequipment/compatiblenetworkingequipment.aspx) Note For Pacific Rim countries, the Router compatibility page is different for each country: Australia: http://www.xbox.com/en-AU/support/xbox/live/faq/routers.htm (http://www.xbox.com/en-AU/support/xbox/live/faq/routers.htm) Hong Kong: http://www.xbox.com/zh-hk/live/connect/routercompatibility.htm (http://www.xbox.com/zh-hk/live/connect/routercompatibility.htm) Korea: http://www.xbox.com/ko-kr/live/connect/routercompatibility.htm (http://www.xbox.com/ko-kr/live/connect/routercompatibility.htm) New Zealand: http://www.xbox.com/en-NZ/support/xbox/live/faq/routers.htm (http://www.xbox.com/en-NZ/support/xbox/live/faq/routers.htm) Singapore: http://www.xbox.com/zh-sg/live/connect/routercompatibility.htm (http://www.xbox.com/zh-sg/live/connect/routercompatibility.htm) Taiwan: http://www.xbox.com/zh-tw/live/connect/routercompatibility.htm (http://www.xbox.com/zh-tw/live/connect/routercompatibility.htm) Note For European countries, all compatible routers are exactly the same: Europe: http://www.xbox.com/zh-SG/live/connect/router.htm (http://www.xbox.com/zh-SG/live/connect/router.htm)

Note If you are not using a router to connect to Xbox Live, the Diagnostic Server readings should all show a positive (pass) test result (1).

Back to the top

Error Codes Associated with MTU tests

The following table gives the error codes associated with MTU tests that pass or fail. The Success code is displayed for each successful test. Failures may be caused by DNS failures, memory shortages, or diagnostic server problems.

Error Code	Value as displayed in Troubleshooter	Comment
XONLINE_E_LOGON_DNS_LOOKUP_FAILED	0x8015190
XONLINE_E_LOGON_DNS_LOOKUP_TIMEDOUT	0x80151904
E_OUTOFMEMORY	0x8007000E
XONLINE_E_INTERNAL_ERROR	0x80150007	Failure is indicated if a return value is received from the XDS server, but it is not what you expected.
XONLINETASK_S_SUCCESS	0x001500F0	Everything is good. If you do not see this code, the test results are not necessarily valid. For example, the MTU problem flag cannot be trusted.

Note If you are not using a router to connect to Xbox Live, the Diagnostic Server readings should all indicate a positive (pass) test result (1).

Back to the top

Diagnostic Servers

For additional information about Diagnostic Servers, visit one the following Web sites:

United States

http://www.xbox.com/en-US/support/connecttolive/xbox/connectionmethods/diagnosingconnections.htm (http://www.xbox.com/en-US/support/connecttolive/xbox/connectionmethods/diagnosingconnections.htm)

Pacific Rim

Australia: http://www.xbox.com/en-AU/support/xbox/live/start/connect/diagnose-dash/default.htm (http://www.xbox.com/en-AU/support/xbox/live/start/connect/diagnose-dash/default.htm)
Hong Kong: http://www.xbox.com/zh-HK/live/connect (http://www.xbox.com/zh-HK/live/connect)
Korea: http://www.xbox.com/ko-kr/Live/Connect/diagnosing.htm (http://www.xbox.com/ko-kr/Live/Connect/diagnosing.htm)
New Zealand: http://www.xbox.com/en-NZ/support/xbox/live/start/connect/diagnose-dash/default.htm (http://www.xbox.com/en-NZ/support/xbox/live/start/connect/diagnose-dash/default.htm)
Singapore: http://www.xbox.com/zh-sg/Live/Connect/diagnosing.htm (http://www.xbox.com/zh-sg/Live/Connect/diagnosing.htm)
Taiwan: http://www.xbox.com/zh-tw/Live/Connect/diagnosing.htm (http://www.xbox.com/zh-tw/Live/Connect/diagnosing.htm)

Back to the top