We have a reverse proxy server setup (IIS + URLRewrite) that forwards external requests to an internal web application. The reverse proxy simply rewrites the external request and forwards it to the internal server which does its work -- rewrites the response and sends the response back to the client.

Problem is -- we're seeing a 5 second delay introduced on pretty much ALL requests. Without the reverse proxy -- the same request direct to the internal web application work fine (testing from internal clients).

This leads me to think this is a DNS related issue.

The lookups from the internal server must be timing out -- then the DNS server has to go out to the internet to ultimately get a response. How can I confirm this? What is the typical way to handle this issue if this is the problem?!


Run wireshark on the reverse proxy and see what's slowing it down. That will show network traffic and the DNS requests.

If that won't show it, if you need more internals, then run the Windows Performance Analyzer Toolkit on the reverse proxy and run your test.

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