I am using two CRS317-1G-16S+ switches running simple Bridge VLAN filtering. Other than using mgmt access vlan interface I am not using any L3 at the moment.
On both switches ports SFP+1 and SFP+2 are running S-RJ01 SFP modules.
Ports SFP+1 on both are going to Brocade distribution switch. Ports SFP+2 are connected together creating a loop. Brocade configured to be root for RSTP with priority set to 0. RSTP enabled and MT2 put its SFP+2 port in alternate state.
Currently both Mikrotiks are on my desk not handling any traffic. I am testing them before putting them in the field.
Weird behavior 1: Since yesterday port SFP+2 (which is supposed to be alternate so disabled) flapped 139 times.
Weird behavior 2: After following some suggestions from this forum to try and disable speed negotiation for SFP module I disabled Auto negotiation and forced speed to 1G baseT full. This caused unexpected effect. Both Mikrotiks were running SFP+2 ports as designated. No switch puts port in alternate state.
So my two questions are
- Why alternate port is flapping?
- Why forcing SFP module to certain speed prevents RSTP election? Am I supposed to enable something else?
Edit: Typo in title
