I would like to understand the meaning or implications of an ATA (SPA-112 in this case) having settings for:
- min (minumum?) SIP port
- max (maximum?) SIP port
- line 1 (or line 2) SIP port
For which I can seemingly enter anything I want into any of the 3 fields above. Now combine that with what I'm told by voip.ms, which is that they support only these SIP-port values:
- 42872
- 5060
- 5080
Now I want to put two ATA's on my LAN (to have 4 lines because 4-line ATA's are either rare or stupidly expensive). Each ATA has 2 lines. Each line has a place to enter a SIP port value. If I understand how NAT-keep-alive communication works, and how the voip provider (SIP server) communicates with an ATA behind a router, it might be impossible for two different LAN devices to be addressable from an outside server unless they are using different ports. Yes? Which means I need the ATA's to use different SIP ports? But each of the two lines can use the same port? So ATA-1 can use 5060 for both line 1 and 2, and ATA-2 can use 5080 for it's line-1 and 2?
And given all that, of what use is the port-range settings?
And finally, is the ATA supposed to tell the voip provider what sip port it wants to use - but in this case voip.ms does not really allow such flexibility? Or is it the voip provider (ie SIP server) that is in control and you must know ahead of time (and set your ATA accordingly) to the sip port that the SIP server wants to use?
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