[Users] openser behind provider nat

[Silvano Galliani (kysucix)]

Hi.
I would like to use openser as a sip proxy under my provider NAT.

Here is my situation:

Sip client (software or hardware)
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Milkfish with openser that's also the router and firewall that does NAT

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Nat of my internet provider with public ip (fastweb.it)

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Sip provider (skypho.net) (it has also a sipproxy)

Can I make it working? How? Because I tried but even registering fails.
bye
kysucix