><p>Istio will use the following default access log format if <code>accessLogFormat</code> is not specified:</p><pre><code class=language-plain data-expandlinks=true data-repo=istio>[%START_TIME%] \&#34;%REQ(:METHOD)% %REQ(X-ENVOY-ORIGINAL-PATH?:PATH)% %PROTOCOL%\&#34; %RESPONSE_CODE% %RESPONSE_FLAGS% %RESPONSE_CODE_DETAILS% %CONNECTION_TERMINATION_DETAILS%
\&#34;%UPSTREAM_TRANSPORT_FAILURE_REASON%\&#34; %BYTES_RECEIVED% %BYTES_SENT% %DURATION% %RESP(X-ENVOY-UPSTREAM-SERVICE-TIME)% \&#34;%REQ(X-FORWARDED-FO