On a on a switch that only support span, and dont support rspan, as long as span only allow destination port to be on the same switch as the source, why cant we connect two switch ports together with a simple straight/cross cable on the same switch, one of the ports - destination for span, another - port for VLAN to traverse the mirrored traffic across the network to another switch. If the two ports are in different VLANs (eg. 10 and 11) and ports are in access mode?
Switches are MAC bridges - they learn source MAC addresses and forward by destination MAC addresses. They don't work like repeater hubs.
If you connect a monitor port to another (production) switch it'll learn all mirrored frames' source MACs on its ingress port, messing up its source address table. Subsequently, it'll forward frames destined for the original source MACs out towards the monitor port - messing up the mirroring switch's source address table as well, or simply get the frames dropped there, depending on the monitor port settings.
Untagged frames can actually be monitored into a port configured for an untagged (and otherwise unused) VLAN. Since the frames are likely flooded to all VLAN ports you'll have to take care that you 'guide' the frame flow to where you want to analyze it and don't congest your production ports with it.