https://documentation.meraki.com/MX/Networks_and_Routing/Configuring_VLANs_on_the_MX_Security_Appliance ... View more

To be considered compliant with 802.3af or at, the midspan must deliver between 48 and 57 Volts. ... View more

To confirm, you are asking can a Meraki MR42 be connected with a Mikrotik Hex PoE router?   Model numbers would be best to confirm, but it looks like the Mikrotik is 802.3af/at PoE so it should power the MR42 fine and shouldn't have issues.   @MeredithW possibly this is better suited for the Wireless board? ... View more