Challenge 1: Which Site Serves an Unmatched Host Header —
Solution Walkthrough

The answer: site-a.example serves this request.

Why:

The request's Host header (unknown-domain.example) doesn't match
site-a.example's ServerName or site-b.example's ServerName -- it
doesn't match anything at all. Per this chapter's own material, an
unmatched Host header is not an error and doesn't fail -- Apache
silently falls back to serving whichever VirtualHost block was
defined FIRST for that shared IP:port. Since site-a.example was
defined before site-b.example in the config, site-a.example is the
default for this IP:port and answers the request, even though its own
ServerName has nothing to do with "unknown-domain.example."

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise checks that the reader knows the specific, concrete
rule governing unmatched requests -- first-defined-wins, not an error
response -- since assuming an unmatched domain simply fails is one of
the most common incorrect assumptions about Apache virtual hosting.