Good morning everyone. I'm running a business where 5 locations communicate with each other with MPLS managed by the ISP.
Due to high costs and the idea of creating a VOIP telephone switchboard to communicate between the various offices, they decided to cancel MPLS and called me to propose an alternative solution.
I was thinking of using gre /30 tunnels for the data part and managing the routing with RIP. The doubt arises, if by chance they wanted to insert a backup connection on each of the 5 offices. Maybe in that case it's better to use a VPN that doesn't need a public IP on both ends.
Also, in order to have no NAT in the telephony part, I was thinking of using L2TPv3 to guarantee a Layer2. What do you think about it, am I proposing a reliable solution? Or am I completely off track?
I am attaching a diagram of how I planned to structure the network.