NSX management cluster DNS issues observed while secondary DNS is functional and present.
Article ID: 427432
Updated On:
Products
Issue/Introduction
System services and functions may be impacted if the primary DNS server is unreachable. Despite having valid secondary DNS servers configured, the system may not fail over to these servers before internal service timeouts occur.
Common symptoms of this DNS timeout behavior may include:
- Repository synchronization (Repo Sync) failures between nodes; this may be seen as an upgrade pre-check failure or on the management node GUI: NSX Manager node shows reposync status as "Down"
- Appliances failing to load in the GUI and showing the cluster as "Unavailable," even though managers are healthy: NSX Manager appliance page shows degraded state due to DNS
- Alarms for FQDN lookup and reverse lookup failure: Manager FQDN lookup failure alarm on NSX or NSX-T Manager FQDN Reverse Lookup Alarm
Environment
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VMware NSX
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VMware NSX-T Data Center
Cause
The internal service timeout for several NSX components is configured to be shorter than the standard operating system DNS failover threshold. When the Primary DNS server is non-responsive, the system services time out while waiting for a response, preventing the resolver from attempting the next configured DNS server in the list.
Resolution
To resolve this issue, ensure the Primary DNS server is reachable or update the configuration to a functional server.
Validate DNS Connectivity
Log in to the NSX Manager CLI as the root user. Test connectivity to the DNS. If the following commands return 3 timeout values before the secondary DNS returns a reply, this KB may be relevant:
Forward lookup:
dig <FQDN of Manager> +short
Reverse lookup:
dig -x <IP of Manager> +short
Update Configuration
If the Primary DNS is unavailable, update the appliance network settings to ensure a healthy, responsive DNS server is listed as the first (primary) entry.
Refer to the following guide for steps: Updating DNS server details for NSX-T Manager cluster
Once the primary entry is corrected, services should recover automatically, alarms may take some time to clear.
Additional Information
For specific examples of how this behavior manifests, refer to:
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