Hello,

I'm on a fiber connection with an Ethernet outlet right in the building. My ISP is responsible for the connection up to that outlet. I assume that they use professional equipment.
Today my connection went down and a long troubleshooting procedure with a not so forthcoming support ensued. I tried different devices and different cables without success while they insisted that their equipment is working properly. The two major test subjects were a stationary computer with two Ethernet interfaces and a router, both of them failed to establish internet connection on either NIC.
Then I decided to change the MAC address on the connected NIC of my computer and boom, it went online immediately. I did the same thing to my router and also that started working again.
So somehow the ISP's DHCP server had managed to "ban" all my three MAC addresses, how can that be? What went wrong on their side?

Any help will be apprecited.
I didn't find the right solution from the Internet.

References:
https://arstechnica.com/civis/viewtopic.php?f=10&t=1371907
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Thank you