Wednesday, February 20, 2008

VISTA networking sometimes blocks outbound traffic

Strange things happen all the time ;) That's the funniest.

So, I have (hopefully to put that into the PAST) some strange problem under VISTA with my Marvell Yukon Ethernet NIC and my Linksys' WRT54GL.

From time to time it appears that I don't outbound traffic to ports like HTTP, FTP, POP, IMAP, etc. But I have outbound traffic via ICMP like PING, TRACE, ECHO. What is going on ?

I did a little research over the Internet and a number of posts came out. The most descriptive one I found is here.

It appears that VISTA is trying to impress us and play hard with the network adapters on some lower layers of the OSI model.

And so, I disable the "IPv4 Checksum offload", the "TCP Checksum Offload (IPv4)" and the "UDP Checksum Offload (IPv4)", restarted and looking forward to see the change. This you can do from:

  • Control Panel -> Network Connections
  • Right click on the desired network connection
  • Select PROPERTIES (you will be prompted from the UAC that this requires administrative permission)
  • Click on "CONFIGURE" button just bellow the name of the Network Adapter used for the connection
  • Go to "Advanced" tab
  • Find all the "[something] Offload (IPv4)" and select "DISABLED"

OK, I'm sure we are all impatient for the SERVICE PACK 1, which is expected to come with Windows Update in mid-March.

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