User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0a2) Gecko/20120210 Firefox/12.0a2 Build ID: 20120210042013 Steps to reproduce: Changed network - from normal network to VPN (for example) Lose network connection and reconnect with Firefox running all the time Actual results: Firefox can't load any web page and requires restart to start working again Expected results: Firefox should be able to detect resetted/changed network connection and react

What type of VPN are you dialing? What software are you running? Is it a split-tunnel VPN? Is there a proxy involved on the VPN side?

I'm using Cisco AnyConnect ( PPTP VPN (Dial-up VPN) ) I think that there might be some proxy server (because there is system which is monitoring every website i'm visiting and sometimes i'm losing my login (need to login again)) Not sure about split-tunneling, but i think that whole connection is redirected to VPN

Wrong. Cisco AnyConnect is SSL VPN

Thanks for that - I don't have any Cisco AnyConnect setups to test (mainly use SonicWall products) Before you connect to the VPN what are your proxy settings (Tools -> Options -> Advanced -> Network)? After you connect to the VPN what are your proxy settings? If use system proxy settings is shown, please check the Internet Options control panel for the system settings.

It's set to "Automatically detect proxy server settings"

Matti -> Do you know how to detect if Firefox is using a proxy at any given time? My working theory is there is a proxy on the other side of the VPN and Firefox only detects this on startup.

untested but http://browserspy.dk/connections.php seems to detect a proxy

HaWaN-> Can you use the link in comment 7 before connecting to the VPN, connect to the VPN, restart Firefox and revist the link?

After connection with AnyConnect there is proxy max connections per hostname 1 max connections 0 Before there is no proxy and 6/6 connections

Try the following: Do not connect to the VPN Browse the net Connect to VPN Confirm Firefox can't resolve Go File -> Work Offline (enable) Go File -> Work Offline (disable) Check if Firefox can browse (Found an old bug that says this re-picks up proxy settings)

Weird... But after update to 10.0.1 issue is gone... If I remember Work Offile enable/disable was helping here too

Err... I was too fast... After disconnection from VPN there were "unable to connect to server" error page and after refresh there is error page with "unable to find proxy server" enable/disable offline mode resolved this error page

Matti -> You think it is time to kick to Core/Networking? I haven't been able to find any exact duplicates yet (aside from a few incomplete reports)

I also have this problem, It's infuriating. Using Fortinet FortiClient SSLVPN version 4.0.2148 to connect to my corporate VPN. Other Browsers have no problem, Chrome and IE. Firefox 20.0.1 is essentially unusable with a VPN.

I confirm that this bug still persists adn that when using the Cisco AnyConnect a proxy is used for navigation inside VPN. Its like Steven Lagou says: Other browsers can handle the network change but for some reason FF can't even with the option to use the system proxy settings. BR Cybern

daniel is actively working on this scenario in bug 939318

I have the same problem running my Firefox 31.2.0 on the esr update channel on a Windows 7 machine. Every time I switch wifi-networks or use CISCO VPN connection, firefox does not connect to the internet. A restart fixes the issue immediately. I came here looking for a solution, and even looked at bug 939318 where I did find a patch. But I don't seem to understand how I can incorporate that patch into my version without having to build the whole thing from source. Could someone please tell me how I apply the patch at the given bug? Sorry if this is the wrong forum for the question. Thanks

(In reply to Vaibhav Agarwal from comment #17) > > bug 939318 where I did find a patch. But I don't seem to understand how I > can incorporate that patch into my version without having to build the whole > thing from source. Could someone please tell me how I apply the patch at the > given bug? that's what you have to do with a patch :) one thing you could do is to run the current nightly to verify the fix in your environment. Its not something that meets the uplift criteria so I would expect to it be released as part of Firefox 35.

I wonder if this bug is gonna persist for ever.. Does firfox hate corporate users with SSL VPN connections so much ;)

I've been having this same issue for a few months now. Firefox works just fine on my laptop at work. It works just fine on my laptop at home before I connect to my corporate VPN. It works not all (more accurately, I get only "server not found" errors). If I close the FortiClient software, Firefox will work fine again. Based on advice here, I've tried going into offline mode and coming back. That doesn't help. The only thing that seems to work, so far as being able to use Firefox while connected to my VPN, is turning Firefox off and turning it back on again. Windows7 FF version 39.0.3 FortiClient 5.2.4.0650

Windows 7 FF 39.0.3 Cisco AnyConnect Secure Mobility Client Ver: 4.1.02011 I am connecting to Intel VPN and of course there is a proxy sitting behind. I browse internet perfectly, and then I connect to VPN above, and the Firefox connection is lost. Only way out of this - 1: Restart Firefox. 2: Goto settings - advance - Network - connection-setting - and then 'toggle' between "Auto detect proxy settings" & "Use system proxy settings". The interesting fact is that - this toggling is necessary, the Firefox-connection-lose issue happens in both of these options..but once toggled to another mode, the connection is back to normal.. This bug seems to bother so many people who are connected to company VPN and want to work from home. If it sounds reasonable then please increase the priority to fix it..

Windows 8.1, FF 44.0.1 Cisco AnyConnect 4.1.06020 to Intel VPN (with proxy) Same problem as described above. I installed toggle VPN add-on which makes it easy to workaround the problem, but it's still annoying. MSIE and Chrome are also installed, neither of them has any problem with switching on/off the VPN. In system proxy settings, both "automatically detect" and "use script" are checked.

(In reply to KCN from comment #20) > I've been having this same issue for a few months now. Firefox works just > fine on my laptop at work. It works just fine on my laptop at home before I > connect to my corporate VPN. It works not all (more accurately, I get only > "server not found" errors). If I close the FortiClient software, Firefox > will work fine again. > > Based on advice here, I've tried going into offline mode and coming back. > That doesn't help. The only thing that seems to work, so far as being able > to use Firefox while connected to my VPN, is turning Firefox off and turning > it back on again. > > Windows7 > FF version 39.0.3 > FortiClient 5.2.4.0650 After posting this report, I switched to ESR channel and the problem was pretty much mitigated. However the problem has reappeared for me. I've now switched to the regular update channel and am on version 44. The problem is the same as before. At this rate, I'll be forced to change browsers since I can't afford to reload all my tabs every day.

Still exists.. Oh Dear.. I am sure Firefox hates IT employees around the world.

Having the same issue here with FF 49 and Cisco AnyConnect 4.2. I don't think this should be status "RESOLVED"

same issue un FF 50.0.1 and cisco any connect, im trying to replace chrome with FF but this issue is very annoying, and developer dont seem to be interested on this issue so i will have to get back to chrome and the devil... sorry for this.

I have the same issue with FF 49.0.2. I am connecting by privoxy proxy. From time to time FF stops connecting to websites, and displaying immadietly info that it can't connect to proxy server. In the same time I see that FF is not connecting to privoxy at all (by privoxy activity icon in tray), but other browsers have no problem in the same time. If I change the setting FF to connect net directly it won't fix anything, just message will be different (couldn't connect to website). Only firefox restart is the proper fix. This bug is hard to reproduce, rare, but still annoying as hell.

For me this is very easy to reproduce and happens whenever I connect / disconnect my Cisco VPN. I have to update the proxy settings. Fortunately, there are these little helpers that allow you to change proxy settings by 1-click. Still: this is annoying as for me this is necessary minimum twice a day.

Same with me. Firefox v45.9.0 with Cisco VPN. Whenever I turn the computer on from sleep, Cisco needs me to reconnect. Then Firefox refuses to connect until I go to proxy settings and turn off the proxy, refresh a webpage, and re-enable the proxy.

This bug had been closed for a while, so if any of you still encounter this issue, would you please file a new bug?