Citrix Access Gateway Enterprise Edition is not able to contact DNS Server

Hello everybody.
Today i would like to write something about a really interesting "error" in a Citrix Access Gateway Enterprise Edition configuration. Our CAGEE was not able to resolve DNS names – a DNS-Server was configured but marked as down. A telnet on the console to port 53 (DNS-Port) to the DNS-Server worked. So why marks the CAGEE the DNS-Server as down and doesn’t use it? The solution is really simple: CAGEE must be able to ping the DNS-Server – then the DNS-Server is marked as up (when it’s reachable) and the CAGEE is able to resolve DNS-Names. A Citrix-technician told me that this is by design an not a bug.

Hopefully this post will help some people to save a lot of time in searching why DNS-Resolution on CAGEE.

PS:
A correct DNS-resolution is normally needed to use an ica-connection to a XenApp or XenDesktop Farm.