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Troubleshooting Link-Local Services in Contrail

Use the troubleshooting steps and guidelines in this topic when you have errors with Contrail link-local services.

Metadata Service

OpenStack allows virtual instances to access metadata by sending an HTTP request to the link-local address The metadata request from the instance is proxied to Nova, with additional HTTP header fields added, which Nova uses to identify the source instance. Then Nova responds with appropriate metadata.

The Contrail vrouter acts as the proxy, trapping the metadata requests, adding the necessary header fields, and sending the requests to the Nova API server.