[[["容易理解","easyToUnderstand","thumb-up"],["確實解決了我的問題","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["難以理解","hardToUnderstand","thumb-down"],["資訊或程式碼範例有誤","incorrectInformationOrSampleCode","thumb-down"],["缺少我需要的資訊/範例","missingTheInformationSamplesINeed","thumb-down"],["翻譯問題","translationIssue","thumb-down"],["其他","otherDown","thumb-down"]],["上次更新時間:2025-09-05 (世界標準時間)。"],[],[],null,["# Troubleshoot BGP peering\n========================\n\nThis guide is for troubleshooting peering issues, such as MD5\nauthentication or on-premises routes without MED values having priority.\n\nFor additional troubleshooting information, see the following:\n\n- [Troubleshoot BGP sessions](/network-connectivity/docs/router/support/troubleshoot-bgp-sessions)\n- [Troubleshoot BGP routes and route\n selection](/network-connectivity/docs/router/support/troubleshoot-bgp-routes)\n- [Troubleshoot Cloud Router log messages](/network-connectivity/docs/router/support/troubleshoot-log-messages)\n\nBGP peer status is `MD5_AUTH_INTERNAL_PROBLEM`\n----------------------------------------------\n\nSometimes the status of a BGP peer includes the following values:\n\n- `md5AuthEnabled`: `true`\n- `statusReason`: `MD5_AUTH_INTERNAL_PROBLEM`\n\nThe first value indicates that you have successfully configured MD5\nauthentication. However, the second value---a `statusReason` value of\n`MD5_AUTH_INTERNAL_PROBLEM`---indicates that an internal error has prevented\nCloud Router from being able to configure MD5 authentication. For that\nreason, the BGP session status is `DOWN`. In this case, you don't need to do\nanything. Cloud Router tries to recover and bring the session back up. If the\nsession is taking more than one hour to back up, contact [Google Cloud\nSupport](/network-connectivity/docs/router/support/getting-support).\n\nFor information about how to check the peer's status, see [Check authentication\nstatus](/network-connectivity/docs/router/how-to/use-md5-authentication#check-status).\n\nCloud Router and peer use different MD5 keys\n--------------------------------------------\n\nWhen you set up MD5 authentication, the Cloud Router and its peer router must\nuse the same secret authentication key. If a mismatch occurs, the two routers\ncannot communicate. If you think that there's been a mismatch, one solution is\nto update the key that is used by the Cloud Router. For information about how\nto make this change, see [Update the authentication\nkey](/network-connectivity/docs/router/how-to/use-md5-authentication#update-key).\n\nIf you're not sure whether there's been a key mismatch, look for troubleshooting\nsolutions in your peer router's documentation. Many routers have logs that\nrecord whether or not there's been a key mismatch.\n\nAuto generated MD5 key is longer than on-premises device can support\n--------------------------------------------------------------------\n\nYou can auto generate the MD5 key by clicking **Generate and Copy** in the UI\nconsole. For more information, see [Add authentication to an existing\nsession](/network-connectivity/docs/router/how-to/use-md5-authentication#add-authentication). If the\nauto generated MD5 key is longer than your on-premises can support, you can\nconfigure MD5 key manually through UI or Google Cloud CLI or API.\n\nOn-premises routes without a MED value are taking priority\n----------------------------------------------------------\n\nIf the Cloud Router receives an on-premises route that doesn't have a\nMED value, the Cloud Router follows the behavior described in [RFC\n4271](https://datatracker.ietf.org/doc/html/rfc4271).\nThe Cloud Router treats the route with the highest\npriority by assuming the lowest possible MED value (`0`).\n\nWhat's next\n-----------\n\n- For more information about how to use Cloud Logging to monitor\n Cloud Router, see\n [View logs and metrics](/network-connectivity/docs/router/how-to/viewing-logs-metrics).\n\n- For additional support, see\n [Getting support](/network-connectivity/docs/router/support/getting-support).\n\n- For information about BGP session states, see\n [BGP session states](/network-connectivity/docs/router/concepts/bgp-states).\n\n- For information about diagnostic messages and session states related to\n Bidirectional Forwarding Detection (BFD), see\n [BFD diagnostic messages and session states](/network-connectivity/docs/router/concepts/bfd-states).\n\n- For issues related to using Cloud Router with Router appliance,\n see\n [Troubleshooting Router appliance](/network-connectivity/docs/network-connectivity-center/support/troubleshooting#troubleshooting-ra)\n in the Network Connectivity Center documentation."]]