Problematic eth1 on some 411AH

Hardware MikroTik hardware general
1

Hi all.
I have some rb411AH with this problem:

  1. cannot autonegotiate at 100Mbit FD but 10 fd
  2. at 10Mbit lose 10% packets
  3. if I try to set manually the speed I definitely lose the board: I must power off then power on the RB (the reboot does not unlock it)
  4. routeros 4.11 + firmware 2.27
  5. changing the routerboard (in the same tower place) the problem remains
  6. the routerboard is in a metallic box correctly grounded
  7. the cable is 25mt, ftp, grounded at bottom
  8. the monitor of eth does not show rx/tx drops

Could it be a interference problem ?
Inserting the cable in a metallic pipe grounded alng the run, could help ?
Inserting a sort of EM filters at both ends of ftp, could helps ?

Have someone an hint ?

thanks

Rodolfo

2

Can you ask tower owner what else located on this tower. If it is some high power VHF equpiment (FM transmitters) - RF interference is possible. Use EMI choke at both sides of cable. As close as possible with 100Base-T device.