Blocking a mac address from getting internet

RouterOS Beginner Basics
1

I tried a firewall rule - chain forward, source address, action=drop.
What does the checkbox next to the address mean? When I check it a “!” appears in it.
The rule does not seem to work - either it blocks everybody’s internet, or nobody’s.
Thank you

2

“!” means “not”, i.e. rule matches any other address than entered.

3

IP > Firewall uses IP addresses, not MAC addresses.

If you want to block a MAC address the interface will have to be in a bridge, then use Bridge > Filter

The ! means NOT - for example !192.168.1.42 means ‘any address except 192.168.1.42’

4

Thank you Sob and tdw

5

Actually, IP - Firewall - Filter can block mac addresses, also by source and destination.