What it means
The router saw its own frames coming back through a bridge port: there is a loop in the network.
Why it happens
- A cable connects two ports of the same switch or bridge.
- Two bridges or switches linked twice without STP.
- A Wi-Fi repeater or VM bridge reflecting traffic.
How to fix it
- Find the extra cable using the port named in the message.
- Turn on RSTP on the bridge (protocol-mode=rstp) so loops are blocked automatically.
- Enable loop-protect on access ports.
Useful tools
Other MikroTik errors
- login failure for user admin from 198.51.100.7 via ssh
- pppoe-out1: terminating... - authentication failed
- pppoe-out1: terminating... - peer is not responding
- dhcp1 offering lease 192.168.88.254 for 00:11:22:33:44:55 without success
- dhcp-client on ether1 lost IP address 203.0.113.25 - received NAK from dhcp server 203.0.1