If a site-to-site VPN is established, what provisioning method should be used for phones?

When a site-to-site VPN is established, using Direct/STUN provisioning for phones is appropriate because this method allows devices to communicate directly with the provisioning server over the VPN. Direct provisioning utilizes the security and private connectivity established by the VPN, ensuring that the devices can securely receive their configuration files and updates.

STUN (Session Traversal Utilities for NAT) is typically used to facilitate communication through network address translation (NAT) environments. In a VPN context, leveraging both Direct and STUN provisioning helps ensure that even if the devices are behind a NAT, they can still connect correctly to the provisioning server for initial setup and ongoing management.

Cloud provisioning would not be suitable in a site-to-site VPN scenario, as it usually relies on external internet connectivity rather than the private tunnel created by the VPN. Local provisioning may also limit flexibility and scalability, which are key advantages of using VPNs for a centralized management approach. Therefore, Direct/STUN provisioning is the preferred method for provisioning phones in this context, as it aligns with the secure, private nature of the VPN while facilitating efficient device configuration.