How to configure freeradius to answer on two IP addresses

All, How may I advice freeradius, to bind to two IP addresses? I tried the Listen option and the bind_address by separating my ip addresses with an whitespace, a colon or a semicolon... Just guessing around, but did not find any documentation about this issue. I can not bind to '*' becaus on an some ip addresses, are other listeners to 1812/13 Thank you. Stefan