We have redundant OSPF routes to our wireless sites, and when the route to the radius server changes (for failover or load-balanced configuration), the source IP picked up by the radius server changes. At least with the Mikrotik user manager, this results in duplicate sessions as it appears to the radius server that two different routers are sending updates.

Is there a way to manually specify a source IP for radius updates, perhaps from a loopback interface that won't change with the OSPF route?

http://wiki.mikrotik.com/wiki/Manual:RA ... Properties

src-address (IP; Default: 0.0.0.0) Source IP address of the packets sent to RADIUS server

Exactly what I was looking for, thanks!