Radius requests answered on wrong interface

[brad at bradandkim.net]

I have a server that I need to sit on two separate network IP addresses
during a transition from one to the other.  I can bind the new IP to the
NIC just fine and it is reachable on that IP.  However, after turning up
this new interface I saw a problem with a redback that auths to this box. 
It turns out that the server was receiving radius requests on the original
IP address, but was responding to them from the new IP address and the
redback was not configured to use this new IP address as a radius server. 
Is this behavior expected?  Simple logic to me would suggest that a
request received would be replied to from the same interface it was
received on, but this is not the case.  Am I missing something simple?  I
am sure I can go in and bind radius to the original IP, but I would like
for it to listen on all interfaces and reply from the interface it
receives a request on.  BTW, this has happened with 2 separate radius
packages, and that is why I am asking here and not on a radius list.

icradius
redhat 8.0

Thanks,

Brad