I spent a load of effort trying to figure out why my new hotspot login screen kept saying "Radius server not responding" when I could see it responding in the log on the core router (running User Manager for Radius).

After a lot of debug, I realized it was because I had configured the Radius server at the hotspot by its canonical address (10.0.0.1), but the responses were independently arriving "from" the address of the point-to-point link between the routers (10.1.0.169) and so were not being matched up with the requests. When I told the hotspot machine that the Radius server was at 10.1.0.169, it all started working… but that's a "gotcha" that just makes it more error-prone to deploy multiple hotspot concentrators.

The hotspot Radius configuration screen has a "Src. Address" field that causes it to send Radius requests so that they appear to come "from" the specified address, which is exactly the sort of feature I need, just on the wrong side. What I'm looking for is the complementary function in the User Manager, to send Radius responses "from" a specified alternate address. Is there such a setting?