Grrr...
 
This is probably a Samba issue - a known one? - but I can't seem to get AD authentications to hit multiple DCs.  Everything goes to the one listed in /etc/samba/smb.conf (which may be a coincidence).
 
I set up several mschap instances like so:
 
mschap mschap1 { ...
   ntlm_auth -s /etc/samba/radius.smb1.conf
}
 
mschap mschap2 { ...
  ntlm_auth -s /etc/samba/radius.smb2.conf
}
 
mschap mschap3 { ...
  ntlm_auth -s /etc/samba/radius.smb3.conf
}
 
I also disabled all PAP, CHAP, and references to "mschap" in all virtual servers listed in sites-enabled.  There is currently no "mschap { ... }" section in modules/mschap.
 
Added this to sites-enabled/campus-inner-tunnel where "mschap" was before:
 
redundant-load-balance {
        mschap1
        mschap2
        mschap3
}
 
Authentication *works*, but all authentications go to the same DC (the one specified in "mschap2").  Running "radiusd -X" shows that all mschap1/2/3 instances are being called, and no authentication *attempts* are being sent to the other two domain controllers.  (1 and 3 aren't failing.  They just aren't *tried*.)
 
Am I going about this all the wrong way?  Is this a known limitation in Samba?  Is there something about ntlm_auth that always references /etc/samba/smb.conf, regardless of the -s option?
 
Comments and criticisms welcome.
 
--J