Asterisk 11.11+Nat

Здравствуйте, Знаю что тема заезжена до невозможности, но просто мыслей уже нет. В первые 30 секунд рвется звонок, в логах ошибка: chan_sip.c: Retransmission timeout reached on transmission hm6EESYOLhFeoM2zIWLFZ-D.Nrs9nJc3 for seqno 31140 (Critical Response) -- See https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions Packet timed out after 6400ms with no response

В sip.conf следующее:

allowguest=no
language=ru
alwaysauthreject=yes
localnet=172.17.10.0/255.255.254.0
externaddr=79.XXX.XXX.XXX
nat=force_rport,comedia
canreinvite=no
media_address=79.XXX.XXX.XXX
directrtpsetup=no
qualify=yes
directmedia=no

У пользователя (внешнего):

[5160]
deny=0.0.0.0/0.0.0.0
disallow=all
secret=secret
dtmfmode=rfc2833
canreinvite=no
context=from-internal
host=dynamic
type=friend
nat=force_rport,comedia
port=5060
qualify=yes
callgroup=
pickupgroup=
allow=g729
allow=alaw
dial=SIP/5160
mailbox=5160@device
permit=0.0.0.0/0.0.0.0
callerid=device <5160>
callcounter=yes
faxdetect=no

в качестве шлюза - отдельная машина Centos. конфиг фаирвола:

$NAT -A PREROUTING -p udp --dport 55000:65000 -j DNAT --to 172.17.10.40
$IPF -A FORWARD -i $WAN1_IF -o $LAN_IF -d 172.17.10.40 -p udp --dport 55000:65000 -j ACCEPT
$NAT -A POSTROUTING -p udp --dst 172.17.10.40 --dport 55000:65000 -j SNAT --to 172.17.10.1

$NAT -A PREROUTING -p udp --dport 5060 -j DNAT --to 172.17.10.40:5060
$IPF -A FORWARD -i $WAN1_IF -o $LAN_IF -d 172.17.10.40 -p udp --dport 5060 -j ACCEPT
$NAT -A POSTROUTING -p udp --dst 172.17.10.40 --dport 5060 -j SNAT --to 172.17.10.1

rtp.conf

; RTP Configuration
;
[general]
;
; RTP start and RTP end configure start and end addresses
; These are the addresses where your system will RECEIVE audio and video streams.
; If you have connections across a firewall, make sure that these are open.
;
rtpstart=55000
rtpend=65000
;strictrtp=no