router eka ALG (Application Layer Gateway) supported router ekak nam witharayi SIP calls weda karanne. ee kiyanne SIP signaling packet eka ethule thiyene IP pawa NAT wenna oni. Router ekata SIP packet eke thiyene sip architecture eka understand karanna puluwan wenna oni.
nethuwa source , destination IP witharak NAT unata SIP packet eka destination ekedi accept karanne nehe.
another reason: public internet eke SIP protocol eka block karala wenna pulwan.
hondama de trace ekak aran wireshark walin analyse karala balanna.
thanks