When linking/connecting the CRS328-24P-4S+RM and the CCS326-24G-2S+RM(both SwOS 2.7) together with a single SFP+ Direct Attach Cable "S+DA0003" (tried swapping each cable end) the only combination not working is CRS328-24P-4S+RM "SFP4" with 326-24G-2S+RM "SFP1/SFP2". Even though the SFP4 "S+DA0003" gets detected on the CRS328-24P-4S+RM just like on the other 3 SFP ports(on which it runs fine), it won't let me access the webinterface of the CCS326-24G-2S+RM through it when my PC is connected to a Gigabit port on the CRS328-24P-4S+RM.

Running/rebooting the CRS328-24P-4S+RM in RouterOS lets me connect again to the CCS326-24G-2S+RM.

The CRS328-24P-4S+RM runs default out of the box SwOS 2.7 with default config.

Unfortunately I'm not responding to help, but throw more fuel on the fire. I have a similar issue with SFP3. I tried 5x S+RJ10 and a pair of S+85DLC03D between two CRS328-24P-4S+RM switches and no matter the combination, SFP3 saw the transceivers, showed link with all of the S+85DLC03D (S+RJ10 always show link regardless of a cable) but no traffic would pass across the link. Moving the transceivers to any other SFP would pass traffic (at varying rates, but that's a different story).

I just wanted to mention that two switches, purchased at the same time, both have a seemingly inoperable SFP port. Perhaps it is a coincidence it is the same port on both switches. I am actually hoping this was on purpose and just not properly documented...

Post if you get anywhere with Support.

There is a known issue with CRS328 running SwOS with SFP3, this port will not forward any traffic under some conditions. This will be fixed in SwOS 2.8, currently you will have to use RouterOS.