Citrix NetScaler virtual machine is one of the VM running in our environment and it was reported that VM loses network connectivity after entering the authentication in the web console of the NetScaler application , Initially we thought it would be some application configuration issue and application owner tried some troubleshooting steps but no luck .Later they went with the new deployment of the NetScaler OVF but still we had the same issue..

Then we started thinking the last changes we made in our environment and it was ESX upgrade to 5.1 to 5.5 with patch 2302651 , based on that we started to investigate the issue and found with the help of VMWARE KB article that after patching the ESXi host to version 5.5 Update 2 (build 2143827), 5.1 Patch 6 (build 2191751), or a later build, we will experience these symptoms and its not the ESXi bug or issue. An upgrade of the Netscaler appliance resolves the issue.

Workaround 1:

Install NetScaler VPX appliance on a previously known good VMware version and build.

Workaround 2:

Add the line hw.em.txd=512 in the loader.conf.local file.

To add the line hw.em.txd=512 in the loader.conf.local file:

1. Log in to the Citrix NetScaler virtual machine appliance as root.
2. Locate the loader.conf.local file on the Netscaler virtual machine appliance by running this command:find / -name loader.conf.localNote: The loader.conf.local file may not exist. If so, create this file under directory /flash/boot.
3. Add this line in the loader.conf.local file.hw.em.txd=512
4. Save the changes.
5. Restart the NetScaler virtual machine appliance.

Reference: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2092809

http://support.citrix.com/article/CTX200278