Hello Team,
I have one router and the necessity set up two hotspot server with two different RADIUS servers.
The first pair hotspot server and the RADIUS server is used for http authentication, the second pair must be used for MAC authentication.
The problem is that the second hotspot server sends requests of MAC authentication on the first RADIUS server in the list.
How to force each hotspot server to send requests to its own RADIUS server?
Thanks in advance
In the documentation I found a string
radius-default-domain (string; Default: ) Default domain to use for RADIUS requests. Allows to use separate RADIUS server per /ip hotspot profile
But it is not clear what should be equal to this option
Thank you all for your help. I talked to myself 
If anyone is interested, please do the following:
In each hotspot service prjfile to determine a parameter radius-default-domain
/ip hotspot profile
add hotspot-address=172.16.0.1 login-by=http-chap,http-pap name=hsprof1 radius-default-domain=http use-radius=yes
add hotspot-address=172.16.1.1 login-by=mac mac-auth-mode=mac-as-username-and-password name=hsprof2 radius-accounting=no radius-default-domain=mac use-radius=yes
In the corresponding RADIUS server to determine the parameter domain
/radius
add address=xx.xx.xx.xx domain=http secret=secret1 service=hotspot
add address=yy.yy.yy.yy domain=mac secret=secret2 service=hotspot
After that, requests from the different hotspot services will go to the appropriate RADIUS server.