Troubleshoot BGP peering

This guide is for troubleshooting peering issues, such as MD5 authentication or on-premises routes without MED values having priority.

For additional troubleshooting information, see the following:


Sometimes the status of a BGP peer includes the following values:

  • md5AuthEnabled: true

The first value indicates that you have successfully configured MD5 authentication. However, the second value—a statusReason value of MD5_AUTH_INTERNAL_PROBLEM—indicates that an internal error has prevented Cloud Router from being able to configure MD5 authentication. For that reason, the BGP session status is DOWN. In this case, you don't need to do anything. Cloud Router tries to recover and bring the session back up. If the session is taking more than one hour to back up, contact Google Cloud Support.

For information about how to check the peer's status, see Check authentication status.

Cloud Router and peer use different MD5 keys

When you set up MD5 authentication, the Cloud Router and its peer router must use the same secret authentication key. If a mismatch occurs, the two routers cannot communicate. If you think that there's been a mismatch, one solution is to update the key that is used by the Cloud Router. For information about how to make this change, see Update the authentication key.

If you're not sure whether there's been a key mismatch, look for troubleshooting solutions in your peer router's documentation. Many routers have logs that record whether or not there's been a key mismatch.

Auto generated MD5 key is longer than on-premises device can support

You can auto generate the MD5 key by clicking Generate and Copy in the UI console. For more information, see Add authentication to an existing session. If the auto generated MD5 key is longer than your on-premises can support, you can configure MD5 key manually through UI or Google Cloud CLI or API.

On-premises routes without a MED value are taking priority

If the Cloud Router receives an on-premises route that doesn't have a MED value, the Cloud Router follows the behavior described in RFC 4271. The Cloud Router treats the route with the highest priority by assuming the lowest possible MED value (0).

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