anchor.diff:      "error":"x509:certificate is valid for 53079ca3-c4fe-4910-78b9-c1a6, not xxx"}}
       </pre>
       - If Gorouter successfully connects to the endpoint, but an error occurs while the request is in transport, such as if Gorouter has not received a response from the endpoint.
  -    - Prior to <%= vars.routing_version %>, Gorouter logged a 502 error for requests that clients canceled before the server responded with headers. If the same situation occurs in <%= vars.routing_version %> and beyond, Gorouter returns a 499 error.
  +    - If a clients cancels a request before the server responds with headers, Gorouter returns a 499 error.
   
   ## <a id="diagnose-stale-routes"></a> Diagnose Stale Routes in Gorouter
   
  -### <a id="stale-routes"></a> What is a stale route?
   A stale route occurs when Gorouter contains out-of-date route information for a
   backend app.
   In nearly all cases, stale routes are self-correcting.
  
positive.code: SSL verification from Gorouter to backends is always on in <%= vars.app_runtime_abbr %> v2.4.0 and later.
  <% end %>
  
  ### <a id="stale-route-symptoms"></a> You might have a stale routes issue if:
  - SSL verification is not enabled
  <% if vars.platform_code == 'CF' %>
  - You do not have Diego Release v2.34.0 or later deployed, which contains a fix that sends unregistration messages multiple times.
  <% else %>
  - You are on <%= vars.app_runtime_abbr %>v2.4–2.7 without the **Keep resending route unregistration message to prevent application misrouting in case of NATS routing tier instability** fix.
  <% end %>
  - You unmapped a route to an app, but traffic to that route is still being sent to the app.
  
  ### <a id="stale-route-causes"></a> Why do stale routes happen?
  When an app container is deleted, due to the app being deleted or moved, or when a route is unmapped, a deregister message is sent to Gorouter to delete the route mapping to that container.
  It is possible that Gorouter does not receive this deregister message.
  When Gorouter misses this message, the route is now considered stale.
  Gorouter still attempts to send traffic to the app.
  
  ### <a id="stale-route-triage"></a> How to triage
  - Verify the state of the deployment.
    1. Run `cf routes` for all spaces and ensure the route is only mapped to the intended apps.
    Sometimes, there can be multiple routes using the same hostname and domain but with different paths.
    If the domain is shared, check all orgs as well.
  - Examine the Gorouter routes table. It might be necessary to check multiple Gorouters, as it is possible that some received the proper deregister message and some did not.
    1. SSH to the VM where Gorouter is running.
    1. To print the entire Gorouter routes table, run:
     `/var/vcap/jobs/gorouter/bin/retreive-local-routes | jq .`
    1. Find the entry for the suspected stale route. Note the values for `address` and `private_instance_id`.
  - Cross-reference the Gorouter routes table entry with actual Long-Running Processes (LRPs).
    1. SSH onto the Diego Cell where the IP address matches the IP address found on the routes table entry.
    1. To get information about all of the actual LRPs, run:
     `cfdot actual-lrps | jq .'`
    1. Look through the actual LRPs to find the instance ID you noted from the routes table.
    If that instance ID exists, and the port in the route table does not exist in the ports section, then there is likely a stale route.
  
  ### <a id="stale-routes-fix"></a> How to fix
  1. Ensure that SSL verification is enabled.
  For more information, see [With TLS Enabled](../concepts/http-routing.html#with-tls) in _HTTP Routing_.
  Using TLS to verify app identity depends on SSL verification.
  If it is disabled, you are likely to run into misrouting, because the fail/prune logic for misrouting is not being used.
  If you disable SSL verification, there is no way to avoid misrouting.
  1. If it is a stale route, then restarting Gorouter fixes the immediate issue.
  If you restart all of the Gorouters and the same issue for the exact same route still occurs, then it is not a stale route issue.
  1. If Gorouter is continually missing deregistration messages, it might be because either the NATS message bus or the Gorouters are overwhelmed.
  Look at the VM usage and consider scaling.
  
  ### <a id="process-stats"></a>Process Stats CAPI Endpoint
  It might be tempting to use the CAPI endpoint `GET /v3/processes/:guid/stats`
  to find out information about the host and ports the app is using.
  However, it is an app developer endpoint, and using this as an operator is discouraged.
  Using the `cfdot` CLI on the Diego Cell lets you view the actual LRPs directly and all at once.
  
  <% if vars.platform_code == 'CF' %>
  On versions of capi-release older than v1.85.0, the information in this endpoint does not show the whole picture.
  <% else %>
  On versions of <%= vars.app_runtime_abbr %> older than v2.8, the information in this endpoint does not show the whole picture.
  <% end %>
  
  Older versions only show the non-tls port.
  However, when using TLS to verify app identity, Gorouter sends traffic to the sidecar envoy using the `external_tls_proxy_port`.
  For this reason, <%= vars.recommended_by %> recommends using the `cfdot` CLI over this process stats endpoint.
  
  ## <a id="gorouter-error-classification"></a> Gorouter Error Classification Table
  
  Error Type | Status Code | Source of Issue | Evidence
  ------------ | ------------- | ------------- | -------------
  Dial | 502 | App or Platform | logs with error `dial tcp`
  AttemptedTLSWith<br/>NonTLSBackend | 525 | Platform* | - logs with error `tls: first record does not look like a TLS handshake`<br/> - `backend_tls_handshake_failed` metric increments
  HostnameMismatch | 503 | Platform | - logs with error `x509: certificate is valid for <x> not <y>`<br/> - `backend_invalid_id` metric increments
  UntrustedCert | 526 | Platform | - logs with an error prefix `x509: certificate signed by unknown authority`<br/> - `backend_invalid_tls_cert` metric increments
  RemoteFailedCertCheck | 496 | Platform | logs with error remote `error: tls: bad certificate`
  ContextCancelled | 499 | Client/App | logs with error `context canceled` <br/><p class="note"><strong>Note:</strong> This status code is never returned to clients, only logged, as it occurs when the downstream client closes the connection before the Gorouter responds.</p>
  RemoteHandshakeFailure | 525 | Platform | - logs with error remote `error: tls: handshake failure`<br/> - `backend_tls_handshake_failed` metric increments
  *Any platform issue could be the result of a misconfiguration.
  
  For each of the above errors, there is a `backend-endpoint-failure` log line<%# "log entry" is preferred. %> in `gorouter.log` and an error message in `gorouter.err.log`. Additionally, the [`access.log`](https://github.com/cloudfoundry/gorouter#logs) records the request status codes.<%# Type "in GitHub" somewhere in the cross-reference sentence. %>
  
  ## <a id="app-errors"></a>Diagnose App Errors
  
  In an **app**, 502 errors can occur in the following ways:
  
  <p class='note'><strong>Note:</strong> Gorouter does not retry any error response returned by the app.</p>
  
  - If 502 errors only occur from one or more particular app instances and not all of the apps on the platform, it is likely an app-related error. The app might be overloaded, unresponsive, or unable to connect to the database.
  - If all apps are experiencing 502 errors, then it could either be a platform issue, such as a possible misconfiguration, or an app issue, such as all apps being unable to connect to an upstream database.
  
negative.code: 
  - **Infrastructure**: issues with your load balancer or network can cause 502 errors.
  - **Platform**: issues with Gorouter or Diego Cells can cause 502 errors.
  See the following sections:
    - [Diagnose Gorouter Errors](#gorouter-errors)
    - [Diagnose Stale Routes in Gorouter](#diagnose-stale-routes)
    - [Gorouter Error Classification Table](#gorouter-error-classification)
  - **App**: issues with an app's load or configuration can cause 502 errors.
  See [Diagnose App Errors](#app-errors).
  
  If you are unsure of the source of 502 errors, see [General Debugging Steps](#debugging-steps) below.
  
  ## <a id="debugging-steps"></a> General Debugging Steps
  
  Some general debugging steps for any issue resulting in 502 errors are as follows:
  
  1. Gather the Gorouter logs and Diego Cell logs at the time of the incident. <%= vars.gather_routing_logs %>
  
  1. Review the logs and consider the following:
      1. Which errors are the Gorouters returning?
      1. Is Gorouter's routing table accurate? Are the endpoints for the route as expected? For more information, see [Dynamic Routing Table](https://github.com/cloudfoundry/gorouter#dynamic-routing-table) in the Gorouter documentation on GitHub.
      1. Do the Diego Cell logs have anything interesting about unexpected app crashes or restarts?
      1. Is the app healthy and handling requests successfully? You can use request tracing headers to verify. For more information, see [HTTP Headers for Zipkin Tracing](../concepts/http-routing.html#zipkin-headers) in _HTTP Routing_.
  
  1. Consider the following:
     - Does your load balancer log 502 errors, but Gorouter does not? This means that traffic is not reaching Gorouter.
     - Was there a recent platform change or upgrade that caused an increase in 502 errors?
     - Are there any suspicious [metrics](<%= vars.gorouter_metrics_link %>) spiking? How is the CPU and memory utilization?
  
  ## <a id="gorouter"></a>Diagnose Gorouter Errors
  
  This section describes how to diagnose Gorouter errors.
  
  - If Gorouter is unable to connect to the app container:
      - If TCP cannot make an initial connection to the back end, Gorouter retries TCP dial errors up to three times. If it still fails, Gorouter returns a 502 to the client and writes to the `access.log`. This might be due to:
  