Are you talking about this topic: https://community.meraki.com/t5/Switching/SFP-ports-on-MS120-48LP/m-p/11685?search-action-id=7956971821&search-result-uid=11685   If you are then you'll see that the opening poster was using single mode gear over multimode cabling which you shouldn't do (at least not without a mode conditioning patch cable). ... View more