Wireshark Question: "TCP checksum offload"

rmartin · 05-12-2008, 09:21 AM

Hello all,

I am having an issue with users in our network connecting to 3 sites in particular (all of which are educational and necessary). Here is the deal:

If I use a proxy (anonymizer) I can connect to these site but if I try and use our regular internet connection it gives me the "IE cannot display this page message".

I ran wireshark on my machine and sniffed the attempted connection to www.joby.com or fablevision.com and got the same results.

According to wireshark it say's:
"checksum: 0xaa4b [incorrect, should be 0x4e79 (maybe caused by "TCP checksum offload"?)] Bad Checksum: True

We use an 8e6 webfilter but this is NOT causing the issue as we are not getting a 'blocked' notice from it. Any ideas on how to clear up this problem? Any guidance/help is greatly appreciated.

Regards

johnwill · 05-12-2008, 02:49 PM

TCP checksum offload is a function of your NIC and drivers. Maybe you need updated drivers or a new NIC?

05-12-2008, 09:21 AM	#1 (permalink)
rmartin Registered User Join Date: May 2008 Posts: 1 OS: XP Pro SP2	Wireshark Question: "TCP checksum offload" Hello all, I am having an issue with users in our network connecting to 3 sites in particular (all of which are educational and necessary). Here is the deal: If I use a proxy (anonymizer) I can connect to these site but if I try and use our regular internet connection it gives me the "IE cannot display this page message". I ran wireshark on my machine and sniffed the attempted connection to www.joby.com or fablevision.com and got the same results. According to wireshark it say's: "checksum: 0xaa4b [incorrect, should be 0x4e79 (maybe caused by "TCP checksum offload"?)] Bad Checksum: True We use an 8e6 webfilter but this is NOT causing the issue as we are not getting a 'blocked' notice from it. Any ideas on how to clear up this problem? Any guidance/help is greatly appreciated. Regards

05-12-2008, 02:49 PM	#2 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 31,329 OS: XP-Pro, Vista, Linux Blog Entries: 1	Re: Wireshark Question: "TCP checksum offload" TCP checksum offload is a function of your NIC and drivers. Maybe you need updated drivers or a new NIC? __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience