Is it permissible to install the DNS server on the same machine as the phone system in split DNS mode?

It is not permissible to install the DNS server on the same machine as the phone system in a split DNS configuration due to potential conflicts and performance issues. A split DNS setup typically involves separate environments for internal and external DNS resolutions. When both the DNS server and the phone system are hosted on the same server, it can lead to resource contention, where both systems may compete for the same processing power and network resources, impacting their overall performance and reliability.

Additionally, managing DNS queries effectively becomes complicated because the requirements and configurations for internal and external DNS can differ significantly. Keeping them on separate servers ensures that each system can operate optimally without interfering with the other, which is essential for maintaining high availability and performance in critical communication systems like a phone system.

In scenarios where a dedicated DNS is not set up, potential risks such as downtime or misconfigured DNS settings increase, which could disrupt phone system operations and reduce overall reliability. Therefore, it's best practice to maintain separation by hosting the DNS server on a different machine.