I have two Cisco SPA504g IP Phones in my remote office across town that need to connect to the UC520 in my main office. I have a SonicWall TZ180 and a couple PCs in my remote office.
In my main office I have an ASA5505 that provides a site-to-site VPN from one of my vendors. An application on my server requires that particular VPN to connect to my vendor. My server provides DHCP and DNS to my PCs, assigning the ASA5505's address as the gateway. My UC520 provides DHCP to my IP Phones, they are on a different subnet than my PCs. The UC520 is behind the ASA5505, does not run firewall, and connects to my POTS phone lines. The PCs are fine, the IP phones in the main office are fine, all works great.
Can my remote phones connect across the internet to my UC520 in my main office?