Hello. (Sorry, my english is basic)
I have a problem with a RB411u, two days ago i reset the configuration of the routerboard to factory defaults because we have a problem (before the system works fine 10 months), when the reset has done the rb doesn't connect with the ethernet cable. The winbox find mikrotik but always write the same error, connection time out if i try to connect with mac.
If i plug serial cable and ethernet cable in rb start ok, and i can enter to winbox, restore the backup, and touch all the configurations, but when i unplug the serial the problem come back, i can't connect with the winbox.
I try to format the nand and put new routeros version (with netinstall), upgrade the firmware to the last version, but it's the same, only works with serial cable.
When i start the rb only with the ethernet cable, I can see the orange led on ethernet and the network speed is in 10 Mbps (no access to winbox, explorer...). When i start with both cables, i can see the green led and the speed is in 100Mbps and all works fine.
The last thing i see, if i start the routerboard with a ethernet cable in a switch, the rb doesn't start correctly, with or without the serial cable, the orange led is always on, and not connect to winbox.
I'm crazy with this problem. One idea open my mind.
Thanks.