Third-party backup (Veeam) fails with "Soap fault. Unknown host. Detail: 'getaddrinfo failed in tcp_connect()'"

Products

• VMware vCenter Server

Issue/Introduction

When you attempt to back up virtual machines or the vCenter Server Appliance using a third-party backup solution (such as Veeam Backup & Replication), the backup job fails.

The third-party backup software logs report an error similar to the following:

Cannot get service content. Soap fault. Unknown host. Detail: 'getaddrinfo failed in tcp_connect()', endpoint: 'https://<vcenter-fqdn>:443/sdk'
SOAP connection is not available. Connection ID: [<vcenter-fqdn>]
Agent failed to process method {Transfer.FileToText}.

Environment

• VMware vCenter Server (All supported versions)
• Third-party backup software (e.g., Veeam Backup & Replication)

Cause

This issue occurs due to a local DNS name resolution failure on the client machine executing the backup (such as the Veeam Backup Server or a designated backup proxy).

The client application generates the specific error string getaddrinfo failed when it cannot translate the vCenter Server's Fully Qualified Domain Name (FQDN) into an IP address. Because the vCenter Server is simply the destination listening passively for incoming connections, this is not an issue or failure within the vCenter Server appliance itself. It is an environmental DNS routing issue or an issue isolated to the third-party backup application.

Resolution

To verify vCenter internal DNS health, perform the following checks:

1. Open an SSH session to the vCenter Server Appliance and log in as root.
2. Run the command: nslookup <vcenter-fqdn> (e.g., nslookup vcenter01.domain.local).
3. Verify that the output returns the correct IP address of the vCenter Server.
4. Run the command: hostname -f to verify the configured FQDN is correct.

If the vCenter successfully resolves its own FQDN and IP address, the appliance's internal DNS services are functioning properly.

Engage your internal network team or open a support request directly with your third-party backup vendor (e.g., Veeam Support). Provide them with the vCenter test results to demonstrate that the appliance is healthy, so they can investigate why their backup application is failing to perform standard DNS resolution to reach the vCenter.

Additional Information

To assist your third-party vendor in their investigation, you can perform basic OS-level connectivity tests from the Windows or Linux server hosting the backup application.

Run tests such as nslookup <vcenter-fqdn> and verify port 443 connectivity (e.g., using Test-NetConnection in PowerShell) from the backup server's base operating system to help the vendor determine if the issue is with the host OS's network configuration or strictly isolated to the backup application itself.