"Temporary failure in name resolution" error while NSX host preparation & while performing VUM tasks on ESXi host

Products

• VMware vCenter Server
• VMware vSphere ESXi
• VMware NSX

Issue/Introduction

Symptoms:

• NSX host preparation fails
• Unable to perform VUM tasks on ESXi, error "Host cannot download files from VMWare vSphere Update Manager patch store.Check the network connectivity and firewall setup and check esxupdate logs for details"
• You will see similar entries in /var/run/log/esxupdate.log file in ESXi host.

esxupdate.log

[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: downloader: DEBUG: Downloading http://vcfqdn:9084/vum/repository/hostupdate/Unknown/metadata_1527045938.zip to /tmp/tmpqfUfjc...^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR: An esxupdate error exception was caught:^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR: Traceback (most recent call last):^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR:   File "/usr/sbin/esxupdate", line 238, in main^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR:     cmd.Run()^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR:   File "/build/mts/release/bora-13635687/bora/build/esx/release/vmvisor/sys-boot/lib/python2.7/site-packages/vmware/esx5update/Cmdline.py", line 105, in Run^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR:   File "/build/mts/release/bora-13635687/bora/build/esx/release/vmvisor/sys-boot/lib/python2.7/site-packages/vmware/esximage/Transaction.py", line 73, in DownloadMetadatas^@
[YYYY-MM-DDTHH:MM:SS] esxupdate: 761348: esxupdate: ERROR: MetadataDownloadError: ('http://vcfqdn:9084/vum/repository/hostupdate/Unknown/metadata_1527045938.zip', None, "('http://vcfqdn:9084/vum/repository/hostupdate/Unknown/metadata_1527045938.zip', '/tmp/tmpqfUfjc', '[Errno 4] IOError: <urlopen error [Errno -3] Temporary failure in name resolution>')")^

Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

Environment

VMware vSphere ESXi 6.x

VMware vSphere ESXi 7.x

VMware vSphere ESXi 8.x

Cause

The ESXi host cannot resolve the DNS name of the vCenter server FQDN.

Resolution

NSX:

• To assist with further troubleshooting this issue, check the DNS settings for the host(s) being prepared. For more information, see Configuring VMware ESXi Management Network from the direct console.

VUM:

• ESXi is not able to resolve vCenter FQDN and IP.
• Check using nslookup on ESXi.
• Update the correct DNS entries on ESXi.