At the end of October I moved a EX3300 two member VC from one site to another and had to change the uplink as it now spans a greater distance on SMF instead of MMF, plus it connects to a 3rd party managed Cisco Stack(3750's).
The day I put it in the uplink didn't come up, spent a good number of hours checking every interconnect only to get the link to return but still not 100% sure how. Since then roughly once a month it seems the clients on the EX3300 site have network performance issues, one point the link was running like a ADSL speed/performance even though the uplink is a 1GB link.
The 2nd time I thought it was the Cisco SFP that had a fault as I tried another one and it worked straight away. The third time a colleague restarted the VC and after it didn't come back up moved the SFP from one VC member to the other and on each fix performance again returned.
I am always worried about restarting the VC as I'm not guaranteed the uplink will return as it hasn't in the past. It was running 12.1R1.9 software previously, it is now 12.3R11.2 as the Juniper site recommended that version.
The previous uplink was on 10GB but the VC was physically located in the same building as the uplink distribution switching(EX4500/EX4200 VC) connected as I said by MMF(OM3). The new site where the EX3300 VC is located connects instead as I said via SMF to a 3750 Cisco Switch stack. I have replaced the Cisco SFP as mentioned and thought it fixed it, well until a month later and the issue returned.
I'm thinking it's hardware related but Juniper support site says the Serial Numbers are not valid, taking that issue up with my Juniper Account Team. The physical port the uplink uses shows no errors input or output. I don't have a spare Juniper 10km long range SFP to test but then if I did I would have to wait at least another month before I would know whether it had fixed the issue or not.
I am suspicious the issue is returning once again and am hoping someone may have an answer for me or some possible tips. I could rollback the software to 12.1R1.9 as it was previously but would rather not have to do that.