When you enable L2TP VPN Connection in a GGSN Node or UMTS test case, the L2TP Node sub-tab defines the Gn L2TP interface node for all SGSN nodes in the test.
With a Gn L2TP node, you can define:
The IP address and routing options... The Starting IP will increment for each node.
The MAC Address to override the Hardware MAC address so the packets sent out of the interface will use the provisioned MAC address rather the Hardware MAC Address.
The Outbound Traffic Port to disable the normal routing function and to force packets out of the selected interface.
Custom port selection... and error injection with the Advanced... button.
The GTP' Node report tab displays the processing and throughput measurements for the emulator.