I am trying to test double tagging with two netgear layer 2 switches. I need help in how to do this. I want a vlan capable device (a firewall of some sort) on one side of a switch with a vlan of 20. This 20 vlan enters the switch and obtains another vlan tag on top of say 40 which then enters another layer 2 switch. Once the packet leaves the second switch I want it to leave with the vlan 40 tagged stripped and be accepted by another vlan capable device with the original vlan 20 tag.
I know how to set up the two switches to communicate with a vlan 40 tag but I do not know how to add that 40 tag to a packet that already has a tag.
Any help would be greatly appreciated.