Avaya SES to FreePBX 2.5 connection

I have an Avaya SES and am able to hit the FreePBX 2.5 server, however, I get the error: “Received incoming SIP connection from unknown peer to …”. I enabled allow anonymous sip calls under General Settings, but still get same error. I am pretty sure I have to configure a trunk within FreePBX to allow calls from the SES but have tried all types of configurations to no avail. Does anyone have any suggestions on how to allow these calls to be processed/routed within FreePBX?