NetScaler Gateway SSL VPN plugin issue. Unable to access internal resources intermittently after connecting to VPN.

VPN plugin stays connected but traffic drops all of a sudden for few seconds and resume automatically.

Workaround
a) Disable Services on the Client PC which generates SSDP multicast Traffic.
b) Create a Windows outbound firewall rule to filter the multicast packet to go over the vpn tunnel.

Solution
Upgrade NetScaler to 11.1 49.16.
Upgrade NetScaler to 11.0 69.123.

Problem Cause

This is due to BUG 643558, where multicast packets over the VPN tunnel causes the MUX channel to go down.

As NetScaler Gateway code does not properly handle the UDP packets destined to Multicast IPs (224.* to 239.* network), and as a result, it closes the MUX connection with vpn-plugin.

So which ever client machine in your environment happens to send Multicast UDP packets, runs into the issue.