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IIS 6.0/DNS/Network Latency Issue

I feel like I'm taking crazy pills.

Over the weekend, many of our javascript-intensive web applications ceased working. Upon further investigation, we realized that many Ajax calls were timing out with the default timeout period of 250ms. Normally, these URL requests would take about 50ms.

Upon even further investigation, we've identified the root issue:
If you navigate to any of our servers using a fully qualified dns address (even one specified in a hosts file), there is a 1 second delay before any HTTP GET request for a text-based document finishes loading. This means our home page, with several js and css files, takes over 7 seconds to load, whereas it should take about 500ms. This only occurs if you navigate to it by its fully qualified dns address. (Ex. http://web1.ourcompany.net/ or http://web2.ourcompany.net/) This also occurs if I create an arbitrary entry in my hosts file, such as "testintranet.com", pointing to one of my servers (Ex. 10.300.400.55).

If we navigate to any of the servers on our network by its short name or by IP address, the issue doesn't appear. (Ex. http://web1/ or http://10.300.400.55/).

So to summarize:
-It's not browser related - IE6,IE8,Chrome, and Firefox are all affected.
-I don't think it's a network problem (we're running a Cisco shop) because IIS correctly responds without delay when connecting by IP or short name.
-I don't think it's a DNS problem because our DNS server quickly resolves *.ourcompany.net addresses, and I bypassed DNS altogether by using a hosts file.
-I don't think it's an IIS problem because 3 separate servers with different purposes, none of which have had any configuration changes in months, all are affected.
-*It's not entirely workstation-specific as almost every computer we've encountered has been affected.

*= I found two PCs so far unaffected - both of which were connected either to our Core or to a gigabit switch. How could it be a physical network problem if only certain HTTP requests with fully qualified host headers are the ones being affected, and not HTTP requests with shorter host headers?

Please, someone help. I don't know how much longer I can take this insanity.
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tenroc2o0o
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tenroc2o0o
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1 Solution
 
nociSoftware EngineerCommented:
Proxy settings? these might [conditionaly through sripting] influence connectivity details.
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tenroc2o0oAuthor Commented:
This turned out to actually be a DNS issue.
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tenroc2o0oAuthor Commented:
No other users submitted a probably resolution.
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