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Could not find the specified XenApp server Error

Posted on 2009-05-03
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Last Modified: 2012-05-06
Everything was working fine, and then one day users could not connect. When anyone would launch any published application they get the error, "Cannot connect to the Citrix XenApp server. Could not find the specified XenApp server."

Heres our setup. One Citrix XenApp server 4.5 on our Windows Domain and in the production network. One Web Interface server 4.5 on our Windows Domain and in the DMZ. One Secure Gateway server 3.1 in a Workgroup and in the DMZ. All three servers have server certificates installed. The WI and SG are on the same subnet and the same switch, as well as our Bluecoat proxy server, if that has anything to do with the process. The XML service is on port 8080, and session reliability is enabled.
 
There were no patches applied, GPO changes, or modifications to any of the Citrix servers around the time the problem started. The network guy does not see any drops or rejects from WI & SG servers to the PS. In fact he does not see any traffic at all going to the PS from those two servers. On the WI, if you change it from Gateway Direct to Direct, users can connect just fine. If you try from the WI, telnet securegatewayserverIP 8080, or from the SG, telnet webinterfaceserverIP 8080, you will see a connection failed. I have tried turning off session reliability, but that didnt make a difference. You can ping both the friendly name and FQDN from every server to every other server.
 
I have built the WI from scratch twice, and the SG from scratch once, but I still have the same problem. I have tried WI 4.6 & 5.1.1, but the results are the same.

I couldnt figure this out Friday night, all day Saturday, and Sunday, so it time too ask the experts. Help!
 
Thanks,
Keith.
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Question by:DanaWilliams
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DanaWilliams earned 0 total points
ID: 24311906
Good news I found the problem. I put Wireshark on the WI to find out what the server was doing. It was a DNS resolution issue. I should have figured this out when the WI (on the domain) couldn't resolve the SG FQDN (not on the domain). I added the SG's IP to the Hosts file. Instead I should have solved the DNS issue. Since the SG was not on the domain, the WI's DNS query ended up getting passed to external DNS server. On the day Citrix went down, another admin had made some changes on the external DNS server. That was the culprit. Once we fixed the issue on the external DNS, Citrix was back up.

Let me explain why it wouldn't work with just a Hosts file entry on the WI. When you launch a Published App, it tries to validate the Server Certificate on the SG. To do that it went to our OCSP (Online Certificate Status Protocol) server. Since the external DNS was incorrect, the OCSP couldn't resolve the name and the certificate could not be validated, so the process shut down.

I learned a whole lot more about Citrix this week.

Keith
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Expert Comment

by:ACECORP
ID: 34240868
Is there a way to prevent it from doing a DNS lookup and force clients to connect solely by IP Address? We have a similar situation, but due to the circumstances, we cannot modify DNS. All users must connect by IP.

We have a citrix xenapp 5 server

Is there something or some file I can edit on our citrix xenapp server that when they click to launch the published application, it connects them by ip address?


Can anyone point me  to what file/files i must edit to do this?

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