Users had intermittent connection problem to published applications when using Citrix NetScaler Access Gateway that provides access to a XenDesktop 7 site.  Citrix receiver would spin saying “connecting to server” and then time out.  The NetScaler was deployed prior to a recent subnet change.  Connections worked ok when the user session was assigned to a server in the bottom half of the new subnet.  If connection was assigned a server in the top half on the new subnet then no connection could be made.

It was determined that the subnet mask for the NetScaler was wrong. The subnet that contained the XenDesktop hosts was recently changed from a /24 to a /23 due to IP shortage.  The resolution to the problem was to update the subnet mask for the NetScaler.

Be aware this change needs to be made via command line on the console of the VPX.  Changing the subnet mask from GUI can break access to NetScaler web GUI.  The subnet mask change can require that you remove and add a route.