What happens if the SNI field is not present during SSL inspection?

When the Server Name Indication (SNI) field is not present during SSL inspection, the system falls back on the Common Name (CN) field of the server's certificate. The SNI field is critical for determining which specific host is being accessed when multiple domains are hosted on the same server. If the SNI is unavailable, the SSL inspection mechanism will reference the CN in the certificate to establish a connection to the appropriate endpoint. This allows the device to still function correctly by identifying the correct site to connect to based on the SSL certificate details.

By using the CN field, the system can successfully complete the SSL handshake and perform inspection as intended. This method is particularly important in environments where multiple services are provided by the same server infrastructure. Ultimately, while the ideal scenario includes having the SNI field present for optimal certificate handling and routing, relying on the CN is a fallback mechanism that ensures continuity in traffic inspection.