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I'm wondering how the CAP-FXS will handle NAT traversal for SIP/RTP, will it be similar to a Cisco SPA112 ATA?
Whenever deploying an SPA112 (or the old PAP2T) it just works like plug and play, even behind double NAT without needing to configure STUN or anything.
It will also stay working if I changeover to a backup ISP (different address) and it registers to the VoIP provider with the new public address.


Will CAP-FXS work similar?

i WILL HAVE TO TEST THOSE BUT IT SHOULD

When I get one or two I'll be sure to report back.... *hint* *hint*

A single SPA112 will work with NAT without anything fancy, but plug a second one in and now SIP ports can't NAT because they are already NAT'd. You need to use a different SIP port for the second SPA112.

Also, the SPA112 tries to UPNP map by default BUT it doesn't try an alternate SIP port so you still have the issue that only 1 works at a time.

They do work great if you set each SPA112 to use different RTP ports and a different SIP port though. NAT maps the RTP without issue because the SIP channel advertises available RTP ports and there is no overlap by config.