I am running Asterisk on a multihomed box – one Ethernet card having a public IP and another having a private IP.
While the IAX works fine (I am able to register with an IAX client and other IAX peers), SIP works only on the Internal Interface – I am able to register as a SIP client from a device on the Internal Interface only. I am unable to register a SIP client with a public IP. Likewise, I am unable to register Asterisk with a SIP provider as a peer.
However, when I use a client (such as Xlite or otherwise) I am able to register just fine. This rules out the possibility of my ISP blocking ports.
I tried using a sniffer on the asterisk box but I dont see any SIP packets either coming into the asterisk box or going out of the asterisk box via the external interface.
Any pointers would be welcome. If you would need any more info on my system settings, please let me know and I will be only too happy to provide them.