PBX IP (SIP)

Prezados,

Tenho nos escritorios PBX IP, em todos uso RB 750G para fazer o roteamento.

Preciso colocar estes PBX IP para se falar, eles usam protocolo SIP, ja fiz varias configuracaos e nao obtive sucesso, internamente esta tudo funcionando, somente o acesso externo que esta totalmente prejudicado.

Vejam ai as regras e vejam se conseguem ajudar.

aplicadas as seguintes regras

[admin@MikroTik] > /ip firewall export
# nov/26/2010 11:22:07 by RouterOS 4.10

#
/ip firewall connection tracking
set enabled=yes generic-timeout=10m icmp-timeout=10s tcp-close-timeout=10s \
tcp-close-wait-timeout=10s tcp-established-timeout=1d tcp-fin-wait-timeout=10s \
tcp-last-ack-timeout=10s tcp-syn-received-timeout=5s tcp-syn-sent-timeout=5s tcp-syncookie=no \
tcp-time-wait-timeout=10s udp-stream-timeout=3m udp-timeout=10s
/ip firewall nat
add action=masquerade chain=srcnat comment="Net" disabled=no out-interface=INTERNET
add action=dst-nat chain=dstnat comment="IIS FAT" disabled=no dst-port=83 in-interface=INTERNET \
protocol=tcp to-addresses=192.168.10.196 to-ports=83
add action=accept chain=dstnat comment=WINBOX disabled=no dst-port=8291 in-interface=INTERNET \
protocol=tcp
add action=dst-nat chain=dstnat comment="IPP SCX-4725" disabled=no dst-port=8082 in-interface=\
INTERNET protocol=tcp to-addresses=192.168.10.10 to-ports=631
add action=dst-nat chain=dstnat comment="IPP ML-2850" disabled=no dst-port=8081 in-interface=\
INTERNET protocol=tcp to-addresses=192.168.10.11 to-ports=631
add action=dst-nat chain=dstnat comment=PBX disabled=no dst-port=5060 protocol=udp to-addresses=\
192.168.10.20 to-ports=5060
add action=dst-nat chain=dstnat comment="WEB PBX" disabled=no dst-port=8083 in-interface=INTERNET \
protocol=tcp to-addresses=192.168.10.20 to-ports=443
/ip firewall service-port
set ftp disabled=no ports=21
set tftp disabled=no ports=69
set irc disabled=no ports=6667
set h323 disabled=no
set sip disabled=no ports=5060,5061
set pptp disabled=no