VxRail upgrade failed at vCenter upgrade with error "Netdumper port in Netdumper configuration is unreadable."

From lcm-web.log:

VCLCMTaskMessageResponse{key='usecase.fb.upgrade.precheck.failure', description='Failed to pre-check virtual machine VMware vCenter Server Appliance (oKlSOqF) meets upgrade requirements.', params=[VMware vCenter Server Appliance (oKlSOqF)]}, VCLCMTaskMessageResponse{key='usecase.error.upgrade.subtask.running.fail', description='Failed to perform upgrade"

From /var/log/vmware/upgrade/requirements-upgrade-runner.log on source VCSA:

"requirementMismatchSpecs": [
                {
                    "text": {
                        "id": "upgrade.netdump.port.get.title",
                        "translatable": "vSphere ESXi Dump Collector Ports!",
                        "localized": "vSphere ESXi Dump Collector Ports!"
                    },
                    "description": {
                        "id": "upgrade.netdump.port.get.msg",
                        "translatable": "Unable to read netdumper port from netdumper configuration!",
                        "localized": "Unable to read netdumper port from netdumper configuration!"
                    },
                    "resolution": {
                        "id": "upgrade.netdump.port.get.resolution.msg",
                        "translatable": "Netdumper port in Netdumper configuration is unreadable. The Netdumper configuration may be corrupted. Please contact customer support and submit a support bundle.",
                        "localized": "Netdumper port in Netdumper configuration is unreadable. The Netdumper configuration may be corrupted. Please contact customer support and submit a support bundle."
                    },
                    "problemId": null,
                    "severity": "ERROR"

From VAMI page of the target VCSA, you will find the upgrade failed with error in the UI as:

vSphere ESXi Dump Collector Ports!
Resolution:
Netdumper port in Netdumper configuration is unreadable. The Netdumper configuration may be corrupted. Please contact customer support and submit a support bundle.

This is a known issue with vCenter 7.0 Update 2. From release note it is said:

• The netdump service does not listen to port 6500 after an update to vCenter Server 7.0 Update 2 from an earlier 7.x release

  After you update your environment to vCenter Server 7.0 Update 2 from an earlier 7.x release, the netdump service stops listening to port 6500 and you see no ESXi dump data.

  Workaround: Open the /etc/sysconfig/netdumper file and modify the NETDUMPER_PORT property to NETDUMPER_PORT=6500. Restart the netdump service by using the command service-control --restart netdumper.

  docs.vmware.com/en/VMware-vSphere/7.0/rn/vsphere-vcenter-server-702-release-notes.html

1.Check the content of the configuration file:

cat  /etc/sysconfig/netdumper on source VCSA：

NETDUMPER_DIR="/var/core/netdumps" NETDUMPER_DIR_MAX_GB=4 NETDUMPER_DIR_THRESHOLD_GB=3 NETDUMPER_PORT=@@NETDUMP_SVCPORT_VALUE@@ <<<<< normally the port should be 6500 NETDUMPER_WEBPORT=8000 NETDUMPER_HOST=@@NETDUMP_HOST_VALUE@@ <<<<< normally this host is vCenter NETDUMPER_LOG_FILE="/var/log/vmware/netdumper/netdumper.log" NETDUMPER_WEBSERVER_LOG_FILE=/var/log/vmware/netdumper/webserver.log NETDUMPER_OPTIONS="-d ${NETDUMPER_DIR} -o ${NETDUMPER_PORT} -l ${NETDUMPER_LOG_FILE}" 

2.Take a backup for the configuration file:

cp /etc/sysconfig/netdumper /etc/sysconfig/netdumper.bk

3.Edit the configuration file

vi /etc/sysconfig/netdumper on source VCSA:

NETDUMPER_PORT=6500

NETDUMPER_HOST=<VC FQDN>

Restart netdumper service

service-control --restart vmware-netdumper

After that, retry the lcm or continue the upgrade from VAMI, it will pass this error.