Look like update ESXi550-201410101-SG 5.5U2 that causes network issues Netscaler VPX appliances. See the discussion at: https://communities.vmware.com/message/2438855#2438855
There is now a validated work around:
1) find where loader.conf is located on NetScaler VM #find / -name loader.conf
For the uploaded NetScaler VM, there are 2 loader.conf: ./flash/boot/defaults/loader.conf and ./flash/boot/loader.conf, we only need to change the first one.
2) add “hw.em.txd=512” to loader.conf, this will change Tx ring size to 512 (note: do not set the ring size to 256, this will cause NetScaler VM core dump)
3) reboot the NetScaler VM
4) migrate it back to a host with latest patches
Citrix released an article on the issue today: