DNS test environment!!

Posted on 2005-04-04
Medium Priority
Last Modified: 2010-04-18
Hello everyone,
  This is going to sound funny. I work for a major cmpany as an IT manager. I am trying to crete a test enviroment that would simulate a slow DNS server, so that we can test some of our software. Any ideas to do this would be great. Below is what they are looking for.

--We need a way to simulate a slow DNS server so that when our server queries the DNS for an external system NAME or IP Address, we can simulate a 10 second response from the DNS server. This will allow us to verify that all queries after the first use the cached value on the server and takes only a couple seconds to complete instead of up to 15 seconds to complete.

Thanks in advance for the help.
Question by:cstallings
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LVL 14

Expert Comment

ID: 13701788
This is a bit of a manual way to do it, but I suppose it might work.

You could input correct IPs for forwarders, then browse a couple of websites from a client which uses your DNS server for resolution.  That would put those entries in the DNS cache of the DNS server.  Then, input incorrect IPs for forwarders (so that your DNS server will not be able to resolve external DNS anymore).  Now, run ipconfig /flushdns on the client computer to clear its own DNS cache, and use it to browse those same sites again.  The second time around, the client computer will ask your internal DNS server for resolution, your DNS server will not be able to get resolution from outside, and it will return the cached record.

I'll try to come up with something better.

Expert Comment

ID: 13704515
I have seen some ISP DNS servers that are almost this slow :)
LVL 14

Expert Comment

ID: 13706173
Oh here's something else you could do --

On the DNS server you want to slow down, go to Task Manager > Processes and set priority for the dns.exe process to "low."    I have no idea how much that will slow things down, but if it's not enough, set some other processes to higher priorities.  Play around with that for a bit until you get the query delay you want.  You'll still want to do ipconfig /flushdns on the client making the query to get a real result.
LVL 33

Expert Comment

ID: 13706259
Another idea might be to copy a large about (gigabytes) of data to or from your DNS test server to another non-related server during your testing.  The large copy (or copies) will generate a load on your server and also limit available bandwidth to your DNS test server.  This should slow it down quite a bit.

LVL 74

Accepted Solution

Jeffrey Kane - TechSoEasy earned 2000 total points
ID: 13747068
You probably want to use MS's WCAT (Web Capacity Analysis Tool - version 5.2) which is part of the IIS6.0 Resource Kit:


The tool can creat all sorts of workload, networkload, etc simulations.

Jeff @

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