After logging onto the computer in the morning I have no problems accessing various websites or my three email accounts. However, after an indeterminate length of time (sometimes 2 hours, sometimes as long as 8 hours) I cannot access any webpages, but instead receive the ‘Page is unavailable’ message. I can temporarily fix the issue by rebooting the computer, although I suspect the root cause may be with the firewall (ZoneAlarm Security Suite version 5) as I am able to access webpages if I disable the firewall. Sometimes if I disable the firewall, then re-enable the firewall I am also able to access webpages without the need to reboot. The computer is running Windows XP Professional.

I have also encountered this issue when using ZoneAlarm. After an arbitrary amount of time I could no longer browse any websites (nor ping any domains). However, rebooting the computer or disabling ZoneAlarm fixed the issue. After a period of frustration and research into this problem, I found the issue is caused by a setting within ZoneAlarm. In the Advanced firewall settings there is an option labeled ‘Allow Outgoing DNS/DHCP in Trusted Zone on High setting’. By default, this setting was not enabled, with the implication being outgoing DNS requests were being blocked, meaning you cannot access internet resources (e.g. webpages) using domain names.

Whenever you browse a webpage using a domain name (e.g. www.siliconkid.com.au) the domain name is translated into the IP address of the server hosting the website (203.10.76.42). This IP address is what is actually used to load the requested website. The domain name is simply a way to allow users to easily remember the address of the website (can you imagine a world where instead of remembering domain names we instead had to remember numerical IP addresses of websites).

Because the allow outgoing DNS/DHCP setting was disabled, ZoneAlarm was blocking the outgoing DNS requests (i.e. outgoing requests for translating the domain names to IP addresses) and thus could not load any websites. By enabling this setting, the problem should stop. The setting can be found by opening the ZoneAlarm window, then click the ‘Firewall’ page and the ‘Advanced’ button. In the window that appears, tick ‘Allow Outgoing DNS/DHCP in Internet Zone on High setting’. Another option ‘Allow Outgoing DNS/DHCP in Trusted Zone on High setting’ is likely to tick automatically, which is normal. Click OK and change back to the ‘Overview’ page to ensure the settings are saved.

Because of the similarities between the ZoneAlarm and ZoneAlarm Security Suite interfaces, you should be able to find a similar setting within ZoneAlarm Security Suite.