Cannot browse some Web sites: yet another cause

Having spent hours yesterday trying to figure out why I could no longer browse a few specific Web sites from my old Gateway Solo 9300 laptop running Linux, whereas all the other Linux and Windows laptops that use my wireless network can browse any Web site, I thought I’d post the solution as Google did not turn up this particular cause.

There are several possible reasons why one may not be able to browse some Web sites: IPv6; the MTU; a black hole router en route; the settings in the various ip_* and tcp_* files in /proc/sys/net/ipv4/, and so on. So, unfortunately I had many avenues to pursue.

My old Gateway Solo 9300 laptop had enabled me to browse the Web reliably via my home wireless network until recently. Suddenly I could neither browse the Sabayon Linux Web site nor access the Entropy package manager’s repository. I could also no longer browse some other Web sites, although most Web sites were still accessible without trouble.

I tried many different things without success, and then finally remembered that I had reconfigured my router a couple of weeks ago because one of my family had reset it whilst I was away from home. Now, when this model of router (BT Home Hub, Version 1.0) is reset it defaults to WEP encryption for wireless networking. However, I normally have it set to use WPA-PSK encryption. So, when I got home I accessed the router’s Web interface via Ethernet from a Desktop PC and changed wireless networking encryption to “WPA-PSK Version: WPA+WPA2″. In the past I had set it to “WPA-PSK Version: WPA”, and thought that setting “WPA+WPA2″ instead of “WPA” this time would not cause any problems. Well, it didn’t on all the other laptops using my network, but my old Gateway Solo 9300 with Linksys CardBus card (‘Linksys WPC54G (EU) v7.1 wireless notebook adapter card’) was different.

As soon as I wondered if the encryption setting was the cause of my problem, I browsed to the BT Home Hub configuration page and changed wireless networking encryption from “WPA-PSK Version: WPA+WPA2″ to “WPA-PSK Version: WPA”. Bingo, my Gateway Solo 9300 running Sabayon Linux E17 Edition and Firefox 4 could browse all Web sites again. Mind you, I also need to have the ipv6 module disabled (I had previously uncommented the line alias net-pf-10 off in the file /etc/modprobe.d/aliases.conf and used the command update-modules) as well as the modifications mentioned in an earlier post (Why can’t I access a specific Web site?). But all those other measures do not solve the problem if the router is configured for “WPA-PSK Version: WPA+WPA2″.

The router’s wireless security option “WPA-PSK Version: WPA” is intended for a network that would only be used by clients configured to use WPA encryption; the router’s option “WPA-PSK Version: WPA2″ is intended for a network that would only be used by clients configured to use WPA2 encryption; the router’s option “WPA-PSK Version: WPA+WPA2″ is intended for a network that would be used by clients configured to use either WPA or WPA2 encryption. So I wonder why there was a problem, as the laptop and CardBus card are configured for “WPA & WPA2 Personal” in nm-applet, and the card supports WPA (TKIP) and WPA2 (CCMP a.k.a. AES).

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