NOTICE[5628] chan_sip.c: Registration from 'user <sip:3813@192.168.5.12>' failed for '192.168.5.25' - Peer is not supposed to register
You have to setup as a "friend" and not "peer".
Set:
type=friend
asterisk, peer, registernotice, chan_sip, registration, user, sip, register, quot,