in product overview the gigabit port of the Switch CRS305-1G-4S+IN is always descriebd as for management.
I currently own no product of Mikrotik, so I don’t know the software SwitchOS/RouterOS.
Is it possible to use it as fifth port for uplink to another gigabit switch to extend this with 4 10G Ports?
According to Marvell specs the 98DX3236 integrates 24 GbE interfaces. So it seems that limitation to single GbE interface (in addition to max supported 4x 10Gbps interfaces) is mandated by device’s form factor only.
Not really … said chip (in addition to 1Gpbs ports) supports 2x 10 Gbps ports and 2x 10/20 Gbps (mind: not even 25Gbps) - the 20Gbps variant is for stacking.
So you better stop pulling imaginary 40Gbps devices out of your head, seems like it’s starting to hurt you
Simply said: the chipset used in CRS305 doesn’t support interfaces faster than 20Gbps, so no Q+ interfaces.
Really, when you’re making up devices, pay attention to the realistic details.
If you had some other chip in mind, then state its official marking, we don’t know what’s BIG chip …