---
title: Why do I see traffic to PassthroughCluster?
weight: 80
---
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Requests going to PassthroughCluster (or BlackHoleCluster) are requests that did not get routed to a defined
service or service entry, and instead end up at one of these built-in Istio request handlers.  See
https://istio.io/blog/2019/monitoring-external-service-traffic/[Monitoring Blocked and Passthrough External
Service Traffic] for more information.

Unexpected routing to these nodes does not indicate a Kiali problem, you're seeing the actual routing being
performed by Istio.  In general it is due to a misconfiguration and/or missing Istio sidecar.  Less often
but possible is an actual issue with the mesh, like a sync issue or evicted pod.

Use Kiali's Workloads list view to ensure sidecars are not missing. Use Kiali's Istio Config list
view to look for any config validation errors.
