Hi,

We have a RB750GL set up as NAT device only (srcnat masquerade and 3 dst-nat rules).
One ethernet port is connected to our LAN and second one is connected to UBIQUITI NanoStation5 with a 40 meter long Ethernet cable.
The problem is, that the ethernet port connected to the NanoStation began to freeze (the LED on that port is completely off when this happens). We have to reboot the RB750GL everytime to turn the port on again. We tried to replace the 750GL with older 750, but the result is the same.
We tried a lot of different RouterOS versions (up to 5.12 and Firmware 2.38) but every version has the same issue.
The ethernet port has changed MAC address to MAC address of our previous router, which is registered with ISP (we no longer use this device).

Anybody might to know what is wrong?

Thanks

The problem is, that the ethernet port connected to the NanoStation began to freeze (the LED on that port is completely off when this happens). We have to reboot the RB750GL everytime to turn the port on again. We tried to replace the 750GL with older 750, but the result is the same.

Please check your other end device Ethernet port, and make sure it works fine.
Try to turn on and off Ethernet port on other end device (Nanostation), and check for the result.