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Problems with DNS on your network can sometimes cause problems with the Flex application. This article briefly touches on known issues with DNS problems and ways to troubleshoot and isolate DNS as the source of the problem.

Symptoms
DNS problems can cause perceived slowness in the software and across the network. This will sometimes be realized by logins taking a long time. These symptoms can be more noticeable with certain areas of Flex and with multiple users. Specifically, Mobile and CAD users often notice this first and will most likely report the slowness to the admins.

There are a few ways you can "see" this on your network from the Flex side:

• Logging into the server takes a long time OR shelling into the Flex environment takes longer than usual (15-20 seconds)
• Spikes in DNS response time from your Performance Monitor webapp

Troubleshooting
One very quick way to isolate DNS as the source of the problem is to move /etc/resolv.conf out of the way:

# mv /etc/resolv.conf resolv.conf.BAK

Once this is done, try logging back into Flex or the server and see if anything changes. If things are much quicker or working as expected, you most likely have an issue on one or more DNS server listed in that file. At this point, follow proper troubleshooting to further diagnose the issue (ping each server, check for any changes to those servers, etc).