Avaya SBC only provide an SDP CAPNEG offer if you select two preferred formats (#1 and #2) or three preferred formats (#1, #2, and #3). Set at least two preferred formats for RTP and SRTP.

Irrespective of the Capability Negotiation check box configuration, Avaya SBC always processes an incoming SDP CAPNEG offer.

For example, you can configure Avaya SBC as follows: Format #1 [AES_CM_128_HMAC_SHA1_80]; Format #2 [AES_CM_128_HMAC_SHA1_32]; Format #3 RTP with SDP capability negotiation for SRTP selected to provide SDP CAPNEG offer.