<h1>Monitoring Blocked and Passthrough External Service Traffic</h1><p>How can you use Istio to monitor blocked and passthrough external traffic.</p></div><p class=post-author>Sep 28, 2019 <span>| </span>By Neeraj Poddar - Aspen Mesh</p><div><aside class="callout warning"><div class=type><svg class="large-icon"><use xlink:href="/v1.21/img/icons.svg#callout-warning"/></svg></div><div class=content>This blog post was written assuming Istio 1.3, so some of this content may now be outdated.</div></aside></div><