RB2011 - WAN (ether1) LED is constantly blinking even if there are no connections from LAN. How to see / debug what is being transfered?

Is there anything connected? There might be discovery traffic for example. Check torch...

Is there anything connected?

From outside, on ISP side? I don't know. I think, there is a switch for several neighbor clients like me.

There might be discovery traffic for example. Check torch...

Thank you for the idea. Torch showed me some activity on the interface.

The most frequent activity is:

protocol = 86dd (ipv6)
src = fe80::xxxx::xxxx::xxxx::xxxx
dst = ff02::2

alhtough IPv6 is disabled on my router!

The less frequent, than previous, but also often is:

protocol = 800 (ip)
src = 0.0.0.0
dst = 255.255.255.255

Then there is some activity from various IP addresses to my public IPv4 address (also from 8.8.8.8 !!!)

Also I see an activity to IPv4 addresses of my public /24 neighbors. Is torch sniffing all the traffic regardless of destination? How can I see their traffic if there is supposedly a L2 switch outside? I thought all the Ethernet hubs were sold out 15 years ago and there are only switches left.

Check if port 1 is set as the master port.

If it is it will explain the blinking if there is no cables plugged in,
if not then the port is most probably dead.

Check if port 1 is set as the master port.

It is not joined with any ports (the default configuration).

If it is it will explain the blinking if there is no cables plugged in

It blinks when the ISP cable is plugged in.

if not then the port is most probably dead.

It cannot be dead because all my Internet traffic goes through it successfully.

Oh sorry I miss interpreted your original post.

I thought the light stayed on when there is on cable plugged into port 1.

Configure a log rule in the firewall to log all traffic.

Then just check it after a few minutes when the lan devices has been disconnected.

Its most probably broadcast traffic