Sometimes, it's not the big network issues that frustrate you the most, but the smaller ones that should be easy to resolve quickly but aren’t. Take, for example, the experience of Bill Lewis, who recently posted a question in our Technical Q&A discussion center about an FTP problem he was having trouble resolving:
“We have an FTP site that is hosted by our ISP,” he reported. “All computers but one can just type the address of the FTP server, and it asks for login, and they access files. But this one machine says it can't find the FTP server—DNS error. It has the same DNS entries and Internet setup [as the other computers].”
TechRepublic members presented Lewis with a number of troubleshooting tips, which could prove useful should you run into the same problem that vexed Lewis.
Particulars of the issue
The machines on Lewis’ network access the FTP site via IE. All machines, including the problem PC in question, access the FTP site using a DSL modem attached to a switch. Initially, the problem PC had IE 5.0 or 5.5 installed, but Lewis upgraded to 6.0 hoping that would solve the problem. Unfortunately, the issue persisted.
Since the problem could lie in a number of places, Mike, of ZASLON, Ltd., offered several suggestions on what to test to determine the cause. Mike felt that the problem was likely a DNS issue and told Lewis to check that first. He said Lewis should perform the following checks to try to isolate the cause:
- Run Ipconfig /all.
- Ping the DNS server from the PC.
- Attempt to resolve the FTP name on the PC with Nslookup ftp.servername.com.
- Purge the cache on the PC via Ipconfig /flushdns.
Maxwell Edison, on the other hand, suggested that the problem might actually be with IE itself.
“I think you may have an issue with the version and or settings with Internet Explorer,” wrote Edison.
He explained that Lewis probably needed to change some of the default settings in IE and offered these instructions:
- On the IE toolbar, choose Tools | Internet Options.
- Click on the Advanced tab.
- Under Browsing, select Enable Folder View For FTP Sites.
- Select Use Passive FTP For Compatibility With Some Firewalls And DSL Modems.
Member nikki96 added that in addition to the above steps, Lewis also needs to disable automatic logon by performing the following:
- Choose Tools | Internet Options.
- Click on the Security tab.
- Click Custom Level.
- Scroll to User Authentication and select Prompt For User Name And Password.
Both nikki96 and Maxwell Edison noted that the option for passive FTP must be selected, but Lewis said that the setting was not available as an option on the PC in question.
Another IE option to check, Mike suggested, was the Automatically Detect Settings selection under LAN Settings. If this option is selected when it shouldn’t be, it could cause the problem.
Member Ginel suggested that Lewis check the hosts file for a possible bad entry and reiterated Mike’s idea to try pinging the IP address of the FTP server. Along the same lines, another member suggested trying to access the FTP server via the Windows command line instead of using the IE browser.
“If that fails,” the member wrote, “suspect a network issue; if it works, suspect an IE configuration issue.” The member added that if accessing the site via the command line is successful, Lewis should try entering the username and FQDN in the IE address bar in the following format: ftp://user@FQDN. The user should then be prompted for a password.
A probable culprit
Lewis reported that he could ping the FTP server and that he could access it via the command prompt. At this point, he was beginning to suspect that IE was the problem. He attempted to repair the IE6 installation but said that did not fix the problem.
Another member suggested that the IE6 installation might have gone wrong and said Lewis should try reverting back to IE5.5. Lewis has concluded that the issue was a problem with IE and said that his next step would indeed be to uninstall it and revert back to IE5.5 sp2. He can then use the recommendations that TechRepublic members made regarding the FTP settings in IE.
The responses to Lewis’ problem provide a blueprint of a process to follow to troubleshoot and isolate such issues. In this case, the fact that Lewis could ping the FTP server and access it via the command prompt clearly indicated that the real problem lay not with DNS issues or the network itself but with the IE browser. The IE settings seemed to be configured properly except for the suspicious absence of one of the options that should have been available in IE6. Its absence and the persistence of the browser connection issue lead to one conclusion: IE6 failed to install properly.
Based on the advice of TechRepublic members, we can distill the following tips for isolating similar FTP connection problems from IE:
- Use ping and ipconfig to check connections.
- Test DNS.
- Connect via the command prompt.
- Check browser settings for passive mode (if behind a firewall) and authentication prompting.