This is a toy HTTP Host routing example, not production server configuration.
What this toy model checks
The trust boundary parses one request, recomputes the Host header, and recomputes the winning row.
recompute before rendering
This is after DNS and TCP
DNS and TCP may get bytes to a server. The Host header can still choose which site that server serves.
one server, many names
Honesty boundary
NOTE: toy HTTP request only; not TLS name indication, proxies, newer HTTP versions, routing policy, auth, cookies, or production web server config.
toy HTTP Host routing only
Summary
The exact Host header chooses the exact virtual-host row; nothing is guessed in the browser or in client code.
Host header selects net-docs