In the documentation here:

https://help.mikrotik.com/docs/spaces/R ... nVLANPorts

I'm using Cisco SFP-10G-SR-S in all my Mikrotik devices and servers some using the X520 as well. They're great and don't run too hot at around 40 degrees C with no additional cooling. They are expensive however, but you may have luck with "Cisco Compatible" SFPs from fs.com or some of the ...

Just my two cents. I'm inclined to think it's your ISP. I'm currently running a CHR on Proxmox 8.3.4 with a dual Intel 10Gbps NIC via PCIe Passthrough (82599ES 10-Gigabit SFI/SFP+ Network Connection (rev: 1)) ISP is Vodafone Ireland FTTH and uses PPPoE served on VLAN10. The default PPPoE interface M...

Tiny typo in /system/disks in Winbox

Double click on slot and statistics tab in Winbox new and old

13. Don't buy a router with 16BMiB of RAM. You might be okay if it's a switch.

I use a CRS309-1G-8S+ as my core switch.

It does have SFP+ ports but you can always use an RJ45 SFP+ converter. The only downside to that is that some of the cheaper ones might run hot.

What model device and what is the installed version of RouterOS?

Configs would also be helpful as no one here can read minds. (I think!)

Also would likely be an issue with the SFP module compatibility. Some cheap SFPs don't work really with Mikrotik switches. Or other manufacturers for that matter.

*) device-mode - do not allow changing CPU frequency if "routerboard" is not allowed by device mode (introduced in v7.17); Really? Why? I can't upgrade one of my routers now because I have to arrange a visit to a data centre just to power the router off to enable the now disabled feature?...

Is the speed still ok if you set the frequency to auto but temporarily disable the fasttrack rule?

I didn't have a chance to check that. Won't have a chance for a while unfortunately as the connection is in demand.