I see some discussions on this topic regularly, so just wanted to le folks know that I have a 10GTek RJ45 1Gbit SFP running cool and flawlessly in my CRS305 under SwOS. This SFP is Gigabit only, so the only requirement is to disable auto negotiation. (All other SFP+ are 10GTek running 10G on multimode fiber, also with no issues . . . )