A voir, c'est la réception du paquet de media qui déclenche ce changement - si tu es curieux, essaie de mettre directmedia=no - ca pourrait rester sur la premiere ip, ou directrtpsetup=no

intéressant aussi, sur la sécurité:
Code:
; IT IS IMPORTANT TO NOTE that if the nat setting in the general section differs from
; the nat setting in a peer definition, then the peer username will be discoverable
; by outside parties as Asterisk will respond to different ports for defined and
; undefined peers. For this reason it is recommended to ONLY DEFINE NAT SETTINGS IN THE
; GENERAL SECTION. Specifically, if nat=force_rport in one section and nat=no in the
; other, then valid peers with settings differing from those in the general section will
; be discoverable.