On the basis of the information that you have provided, the answer is read and follow the documentation, which can be found at asteriskdocs.org/ and in the configs/sip.conf.sample file that should have come with your Asterisk code.
== Using SIP RTP CoS mark 5
– Executing [100@default:1] NoOp(“SIP/2001-00000008”, ““2001” <2001>”) in new stack
– Executing [100@default:2] Answer(“SIP/2001-00000008”, “”) in new stack
> 0x7fbb5c0306f0 – Probation passed - setting RTP source address to 192.168.1.22:40020
– Executing [100@default:3] AGI(“SIP/2001-00000008”, “agi-sayani2.agi”) in new stack
– Launched AGI Script /var/lib/asterisk/agi-bin/agi-sayani2.agi
[Oct 2 17:45:40] NOTICE[3685][C-00000008]: channel.c:4257 __ast_read: Dropping incompatible voice frame on SIP/2001-00000008 of format ulaw since our native format has changed to (gsm|h263)
– <SIP/2001-00000008>AGI Script agi-sayani2.agi completed, returning 0
– Auto fallthrough, channel ‘SIP/2001-00000008’ status is ‘UNKNOWN’