As the SPAN / RSPAN is a LAN feature, there are many limitation when attempted on WAN link. First is the fact that WAN link typically resides on routers. In order to use the RSPAN feature, you will need to first have a trunk link to the out bound router. to carry over the RSPAN traffic. As RSPAN creates a separate RSPAN vlan to carry over the traffic, this is necessary. From there, the router will then need to bridge the traffic as the SPAN traffic will require tags to be carried over when it gets to the destination switch. So in order to do that you will need to bridge the link between the routers that are connected to

your WAN link. Only after that, then you will need to create another trunk link to the switch in new location and then traffic will be directed to the destination you desire. As you can see, this method has several potential problems. Since the WAN link will now need to be bridged, it can only pass traffic from one VLAN, specifically the RSPAN VLAN. So only thing that you will see at the other end is SPAN traffic and nothing else, so the existing VLANs will not be able to get out.