Final answer:
The most secure location for a SQL server that needs to communicate with Internet web servers is the internal network or an isolated VLAN. Both options provide protection from direct Internet exposure, with controlled access. Placing the SQL server in a DMZ or on the Internet would expose it to potential attacks.
Step-by-step explanation:
If you have several Internet web servers that need to communicate with a SQL server, the most secure placement would typically be the internal network or an isolated VLAN. Placing the SQL server in the internal network would ensure that it is behind a firewall and not directly exposed to the Internet, reducing the potential attack surface. An isolated VLAN can provide a similar level of security, segmenting the SQL server from other parts of your network and controlling which devices can communicate with it.
Placing a SQL server in the DMZ (Demilitarized Zone) can be risky as DMZs are partially exposed to the Internet, providing services to external traffic. This can introduce vulnerabilities. Placing a SQL server directly on the Internet would be highly inadvisable as it could be easily discovered and targeted by attackers.