Generally, 100M SFP modules can not be used with SFP+ ports. They sometimes can be used with SFP ports, however there is no guarantee it will work properly until you’ve actually tested the compatibility of the hardware!
Besides using a 100M SFP Module with a 100M-compatible SFP port, there is also the possibility of using a SFP Module with integrated converter. FS offers such a device for ~55€ but at the moment I do not know if it is compatible with an Mikrostil device.
Compatible devices
The MikroTik help page lists the CRS106-5S-1C as being compatible with both 100M and 1G SFP modules:
This unit is compatible with 100Mbit and 1.25G SFP modules
It has 5 SFP ports and 1 Combo SFP or GigE port.
Furthermore, the MikroTik wiki has a list of devices compatible with 100M fiberoptic transceivers – at the time of writing this post:
- CCR1009-7G-1C
- CCR1009-7G-1C-1S+
- CRS106-1C-5S
- CRS328-4C-20S-4S+
- LHG XL 52 ac
- RBD22/D23/mANTBox 52 15s/NetMetal ac²
Besides manually searching the MikroTik site for other compatible devices, I also used Google to search for similar sentences on the MikroTik site. I could not find any other MikroTik device for which any statement about 100Mbit SFP compatibility is being explicitly made.
Incompatible devices
For the following devices I have checked the respective MikroTik help page and it does not list compatibility with 100M SFP modules. This does not automatically mean they aren’t compatible but it’s much less likely. Possibly the help page will be updated in the future to indicate compatibility. I have not physically tested any of those devices with 100M transceivers.
- CRS310-1G-5S-4S+IN
- CRS112-8P-4S-IN
- hEX S
- CRS109-8G-1S-2HnD-IN
- CRS212-1G-10S-1S+IN
Often, the help pages with read something like Compatible with 1.25G SFP modules. This means that standard 100Mbit SFP modules are incompatible.