Windows Vista won't connect to the network - how to fix the problem by making Vista less aggressive on the network

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Windows Vista automatically tunes it's network settings to make the most of the available bandwidth. In some scenarios Windows Vista can fail to connect to the network - this is often due to old routers which don't always quite follow the standards to the letter. There is an excellent white paper titled Windows Vista TCP/IP Networking and IPv6 Migration that explains in quite some detail how Windows Vista tunes it's performance - it's well worth a read. The white paper explains the rationale behind the default settings and the implication of making changes.

If you find yourself in a situation whereby you are unable to access a network then it's worth trying the following from a command line that's running with elevated privilege.

Note: An easy way to run an elevated command line is to create a shortcut to "cmd.exe", right click on the shortcut (whilst logged in as an administrator) and select "Run as administrator".

To view the current TCP optimisation settings issue the following command:

C:\Windows\system32>netsh interface tcp show global

You should receive output similar to the following:

Querying active state...

TCP Global Parameters

----------------------------------------------

Receive-Side Scaling State : enabled

Chimney Offload State : enabled

Receive Window Auto-Tuning Level : normal

Add-On Congestion Control Provider : none

ECN Capability : disabled

RFC 1323 Timestamps : disabled

 

To disable the settings issue the following command:

C:\Windows\system32>netsh interface tcp set global rss=disabled autotuninglevel=disabled

 

Assuming you've typed everything correctly then you'll receive the following output:

Ok.

Now try to connect to the network once again - you may need to "repair" your connection or simply unplug the network cable and re-insert it if it's wired - for wireless just disconnect and reconnect to the network

To set your network stack back to normal once you've finished issue the following command:

C:\Windows\system32>netsh interface tcp set global rss=enabled autotuninglevel=normal

Note that the "autotuninglevel" is set to "normal" not "enabled" as you might expect!