Q: Upgraded to OS X lion and now I cannot connect to the Internet.  Wifi or hard wired. Any ideas?

ALso if you guys click Advanced in Firewall, do you guys have 'Block all incoming connections" or "enable Stealth mode" checked ?

Make sure your applications have access too and are set to "Allow incoming connections". Then re-enable the firewall and test.

For those using Avast there is a known issue according to reply 57 in this thread: http://forum.avast.com/index.php?topic=78646.45

@wifiguru Thanks!

Command 1:

sudo mv  /Library/Preferences/com.apple.alf.plist  /Library/Preferences/com.apple.alf.plist.orig

Command 2

sudo rm  /Library/Preferences/com.apple.alf.plist

Now reboot your machine and then turn the firewall ON after a reboot. Then reboot a couple times and test if everything works.

That worked a treat. Was on with apple support for two hours last night and they couldn't nail it, but you did. Much appreciation! Now I can get back to work! :-)

i do not find this files, should they be in library?

I don't have the Firewall on, I don't have antivirus software and I cannot get on the internet at home or work using wired or airport.  I've already reset SMC.  Help!

ok, im kind of a noob here and really dont know what u r talking about. I opened library/preferences but i dont see the files you mentioned, dont know what file i need to backup and what is that about command 1, can someone break this down for someone with not that experience?

thank you

ok, so i dont really know what i did, but everything seems to be working perfectly. thanks alot for the help. There is also a problem with Java and Lion, so if u r having problems with java try downloading it directly from the apple site. hope it helps.

Thanks

octamm, the file should be in the /Library/Preferences directory. Disable the firewall. Simply run this command:

sudo rm  /Library/Preferences/com.apple.alf.plist

and then reboot with the Mac. Then enable the firewall and test if it  works for you.

More info:  I went to Network Utility and pinged an address on the net with no issue (I can also do netstat and lookup via the Utility interface), but I have no internet connection in browsers, email, twitter app etc.  I've tried the Terminal comands above with no luck.

Geoff,

Have you tried disabling the firewall, checking the DNS setting's, SMC reset and if you have the Avast antivirus sw. ? Some of these have helped folks here.

Deleted Intego software a while back, but it did't get it all, and caused KP in Lion.  So I got ride of it all, but it messed up stuff.  Apple Care phone for an hour.  Reformatted the drive, clean install, and using migration assistant to restore data from a time machine back-up.

I couldn't get on wired after installing Lion.  Eventually, I deleted my Ethernet connection in System Preferences and then re-added it.  After rebooting, I was able to get online.

After downloading and installing lion...my wifi wouldnt even turn on. I kept reinstalling and reinstalling and nothing still. I even called apple and they werent able to help because lion is so new. So today i even went to the genius bar. they wiped my macbook clean back to snow lepord and reinstalled lion again....AFter all of this work, still nothing. I kept looking all for hours on solutions and i stumbled across this which WORKED. I couldnt believe it after all day doing nothing but getting this to work, doing what i did below somehow did the trick. try it out and lemme no if it works

Restart computer without power cord hold down:  "command" "option" "P" "R"

Wait until you hear the 2nd chime then relase

Tried everything here including the other thread... Not working for me. Reinstalled Snow Leopard and the same problem exists... Itvwas working before I installed Lion.

15" Early 2011 MBP 2.2Ghz Hi-Res 8 GB RAM

I had the same problem with my mid-2010 Macbook pro.  I could see and do everything on my local network, either wired or wireless but my Macbook could not see the Internet, including mail, Safari, App Store, etc.  I never have had AVAST on any of my Macs, and my early-2008 macbook (still running SL 10.6.8) could connect wired or wireless to the internet, so I knew that something was amiss in the upgrade.

After reading through all the suggesstions did what someone else suggested:  I went into System Preferences, turned off the firewall, rebooted, checked and was able to connect wired and wirelessly, went back, turned the firewall back on, rebooted, and I'm up and running.  Local network and internet (wired & wireless) work seamlessly now.

I have rebooted several times and everything connects like it should. 

I thank you all for your help and suggestions.