NAT, SIP and same port problems

  • Hi,

    Today I had problems when I powered up a second cisco 7940G VoIP phone. It would not authenticate against my asterisk server. When I checked the states, what I saw was that NAT had allocated port 5060 to my first IP phone, as you would expect.

    I would have assumed that the second phone would simple have been allocated a different random port on pfSense but what was happening from the looks of the state table, was that it was also sending its packets from 5060, but the replies would of course be going back to the first phone.

    I fixed the problem by enabling advanced outbound NAT and setting a static port for one of the phones.

    However whilst its possible to do this manually, should NAT not have know that port 5060 was already in use, and just allocated a different one?



  • You will want to enable static port for the entire subnet… Not just one phone.

  • Cheers,

    I made that change, and I think I understand a little more about NAT now into the bargain.



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