Best of the ISP-Lists

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Know Thy Firewall

Members of the ISP-Tech list solve one subscriber's problem and explain many of the other common problems they've unearthed on customers' computers over the years.

[October 8, 2001]

On the ISP-Tech list in September, MV inquired,

"We have a customer who can connect but is not able to browse, receive mail, ping or telnet. I've tried pinging and browsing to an IP address with no success, so DNS doesn't seem to be the issue. The computer is able to ping its own IP, but times out on all other requests. This is driving me nuts! Help!"

A number of respondents shared their own suggestions:

[LE commiserated] "I have a customer with the same problem. I wondered if it might be a virus, because the customer's virus definition files had not been updated in 1,396 days!"

[CS recalled] "I've had this exact thing happen on older PCs if their DNS settings are set to 'Server Assigned'. Once we changed them to the actual primary and secondary server numbers, it worked."

[FX recommended] "Have you replaced wsock32.dll? We have seen several systems just as you have described, and renaming the current wsock32.dll to wsock32.old, then extracting a fresh version from the cabs, usually fixed the problem."

[PI advised] "Try this: open a DOS prompt and run ipconfig, then see what settings are bound to the interface."

CS suggested it might be the tenacious remains of a firewall:

"I have found that if they installed ZoneAlarm then removed it improperly (without using uninstall) the proxy will kill everything: mail, DNS, HTTP, and telnet. I reinstall ZoneAlarm, then uninstall it, and usually that clears it."

According to MV, CS had the winning answer:

"It was ZoneAlarm. I installed it and everything was fine, then I uninstalled it, and whatever was left in there from the last incomplete uninstall was removed and the computer was able to browse. Thanks!"

—End