/etc/freeradius/3.0/clients.conf

# SITE1
client RADIUS_SITE1 {
        ipv4addr = 0.0.0.0/0
        require_message_authenticator = no
        secret = AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDD
        shortname = SITE1
        virtual_server = SITE1
}

# SITE2
client RADIUS_SITE2 {
        ipv4addr = 0.0.0.0/0
        require_message_authenticator = no
        secret = EEEEEEEEFFFFFFFFGGGGGGGGHHHHHHHH
        shortname = SITE2
        virtual_server = SITE2
}