As the subject says...I'm looking for some detailed info on the WLAN setting, DEFAULT-FORWARDING.

All of the info I've found so far tells me that it prevents direct "client-to-client" (layer2) communications for clients that are connected to the same WLAN interface.

My question is, HOW does direct client-to-client communication take place?

Is this accomplished by taking ALL data RX'd at the AP on the WLAN interface, and re-transmitting it back out the WLAN interface? Or is this done on an individual destination basis?

Here's the situation. There is a streaming CCTV camera connected to a client. The destination for the video stream is on the other side of the CL's AP, over ethernet.

(Edit...the text-diagram below doesn't render as expected!)

CCTV ----> CL1 ------------|
|--------------- AP -----------> CCTV Destination
CL2 ------------|

If the AP has DEFAULT-FORWARDING = YES, does this mean that the entire video feed from CL1, to the AP, to ETH on the other side of the AP, will also be retransmitted by the AP? If the feed is 4 mbps, the AP will also be TX'g 4mbps?

I just did a test using other Mikrotik devices in place of the CCTV camera and the CCTV Destination, and ran a bandwidth test sending from the "CCTV" to the "CCTV Destination", and while monitoring the AP WLAN traffic, the tens-of-mbps being received by the AP, was NOT retransmitted, as reported by /interface monitor-traffic wlan1.

But, I didn't know if Mikrotik maybe doing some voodoo because it "knows" it's a Mikrotik bandwidth test, running. Also, it was important to run this between connected devices, and not to/from the CL/AP at all, and just use this as a pass through, as that how it would be used in the network.

Thanks in advance!!

fN

Think of AP if it was a switch and each connected station connected to separate switch port. And additional uplink port (which is wifi interface, usually connected to device's bridge). This "AP switch" is implemented in wireless driver.

When default-forwarding is enabled, then "AP switch" will forward frames between any pair of ports, including "station ports". And since forwarding is implemented in wireless driver, such forwarded frames never appear outside wireless network (which terminates at wireless interface).
When default-forwarding is disabled, then "AP switch" will only pass frames between individual "station ports" and uplink port but not between station ports.

Since nornal switches and bridges won't send a frame out through ingress port (even if FDB says destination MAC is behind that port), disabling default-forwarding effectively blocks station-station connectivity.

The above is true when both sender and receiver are stations connected to same AP. It's not clear to me how your devices are connected (you're mentioning ethernet which somehow contradicts station-statikn concept), so it's hard to tell how frames actually pass between devices.