Networks

I have also been plagued by this exact issue for a year or more. Mainly as it resolved and reappeared with no reason and no definitive fix. I've had at least 20 users at my office experience this issue with no solutions to be found in internet searches.
The scenario is the same as most others here have described.
A user has a good connection to the internet via a wireless connection at home. They can successfully connect and authenticate to their company VPN via Cisco VPN client. But then no other traffic will flow (no internet, intranet, email icmp, etc). If they connect via wired connection everything works fine.

This does not affect everybody and usually only happens at home (works fine at a hotel or hotspot form the same system and same user).

I narrowed the issue down to a combination of Cisco VPN client, built in wireless LAN on Dell and HP laptops (both of which use a Broadcom chipset), and usually home wireless routers.
The thing I found most perplexing about this was that sometimes the problem would go away for several weeks. I mean all 20 users would all of a sudden start working again. We could not trace this occurrence to any patch event, etc.
Sometimes just installing the latest WLAN drivers from from Dell would resolve the issue. But then a few weeks later it would pop-up again.
I tried everything, updating router firmware, using different versions of WLAN adapter drivers, different Cisco VPN client versions, changing my WiFi security (WEP, WPA, WPA2, None) options, Still I never found a solution.

Anyway Dell finally did enough research and posted a solution, and only finalized it a week or two ago. Here is the link:

http://support.dell.com/support/topics/global.aspx/support/dsn/en/document?c=us&cs=RC956904&docid=152D7D67033477DFE0401E0A5517188F


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The fix is to disable VLAN Priority Support on the WLAN adapter.
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This worked for all my Dell users so far.
The HP WLAN driver doesn't have the option available, but its probably the same thing-still researching. So far the Broadcom chipset is the common denominator between the Dells and HP. And I think they make the chipsets for Linksys wireless routers as well. I was not able to gather enough information for those that had the issue to know all the routers that they had when they had problems, or even if it was only certain firmware versions.

Since this usually only happens at home, my guess is most home routers lack VLAN support and something between the Cisco client, the WLAN driver and the router WiFi support gets confused when a VLAN Priority request is sent or something like that. And since most hotspots/hotels will use a more commercial Wireless router, VLAN is more than likely supported and thus the problem is not encountered. Also the default VLAN priority option is default set to Auto, which may explain why the problem was intermittent.
Of course this is only a guess.

One of my users said their problem went away simply when they switched from cable to Fios-possible but I think probably a coincidence.

I hope this helps everybody out there.

My wife received a laptop from her company a couple of weeks ago. Her laptop had all the symptoms you cited in your post. I tried everything I could: contacted her company helpdesk, contact our Linksys router tech support, adjusted MTUs, forwarded ports, adjusted IP addresses, tweaked VPN settings, adjusted peer response times, etc. Then, I saw your recent post. Turns out that my wife's laptop is an HP with that suspect Broadcom wireless adapter (version 4.40.19.0). I disabled VLAN Priority Support on the network card and... the laptop has been operating for 5 hours straight with no hiccups.

Thanks a lot for the information you provided!

Hello,

I have been having this issue for the last 9 months. Me & my husband tried various different options but with no luck. Our Help Desk also couldnt offer support saying, this is home networking and since it works fine with a public wireless network, our job is done.
It was very very kind of you to post this here. My sincere thanks once again

I have been searching forums, Google etc.. for the past 2 weeks. When I saw your post I new that was it, I tried it and everything works fine. I will pass the info along to our Network Admin. Thank you very much.

My issue wasn't identical in that I could never even contact my gateway to input credentials when running over my home wireless network. I'm using a Dell D620 connecting to a TrendNet home wireless router.

However, once I disabled the VPN Priority (which was set to AUTO), I've had no problems since.

Thanks so much for taking the time to post and help others out!