Cannot download from Intranet sites

Unanswered Question
May 2nd, 2007


We have VPN setup through a Cisco 877w router. Everything works fine, we can share files, browse the Intranet pages but we cannot download files (.doc, .xls) from the page. The browser says folder or files not found. Those files can be accessed via the file server.

Could someone let me know what could prevent it please?


I have this problem too.
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bbaley Tue, 05/08/2007 - 13:52

I don't think it is some issue with the router or VPN setup. You can check it by disabling the VPN on your router and trying to download the files.

trietgiang Tue, 05/08/2007 - 14:44

Thank you for your reply bbaley. I think I didn't make myself clear in the first post: it is ok to download when I am physically in the office; when I am connected to the office LAN via VPN, I can browse the Intranet sites without any problem but I can not download from the Intranet (via VPN)

Best regards,


florent Wed, 05/16/2007 - 05:31

Go to and search for ip tcp mss-adjust. This explains how to manipulate the maximum segment size on your office lan. Your server probably starts sending your requested file with an mtu of 1500. Since it traverses a tunnel that has a smaller mtu and the don't fragment bit is set on your server the router just drops the packets returning an icmp message "df set but fragmentation needed". You problably woud be able to see that on your server using a packet capture program. Just try to lower your server's MTU size of program the "ip tcp mss-adjust" command on your router. Start with a value of 1300 and gradually go up.


Florent Conings


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