Vmware esx cannot synchronize host

Network trace between host and vCenter

1. The first step in a network trace is to verify what vmk is the management network as seen below:

esxcli network ip interface tag get -i vmk0

Output: Tags: Management

Keep changing vmk’s until you have the management network.


2. The next step is to figure out what port number is used for the vmk of the management network in this example we can see vmk0 is the management network:

net-stats -l


PortNum     Type SubType SwitchName    MACAddress     ClientName

33554434      4    0 vSwitch0     00:50:56:01:3b:4b vmnic0

33554436      4    0 vSwitch0     00:50:56:01:3b:4c vmnic1

33554438      3    0 vSwitch0     00:50:56:01:02:da vmk0

83886091      5    9 vSwitch3     00:0c:29:aa:94:59 Test

83886092      5    9 vSwitch3     00:0c:29:2d:d6:3d Test2

In this case the port number is 33554438.


3. The next step is to verify what vmnic is using the port number 33554438 to do this we must run the vsish command as seen below:

vsish -e get /net/portsets/vSwitch0/ports/33554438/teamUplink

Output: vmnic0

we can now determine that vmnic0 is used for management traffic.


4. The next step is to check if firewall rules are enabled by running the following commands:

esxcli network firewall ruleset list | grep vpxHeartbeats


Name           Enabled

———————— ——-

vpxHeartbeats       true


5. The next step is to verify the IP address of vCenter by running the command:

cat /etc/vmware/vpxa/vpxa.cfg | grep server





6. Using the information gathered in the previous steps we can now build your packet capture command as seen below:

pktcap-uw –capture UplinkSnd –uplink vmnic0 –proto 0x11 –dstip -o – | tcpdump-uw -r – -nn | grep “902: UDP”


reading from file -, link-type EN10MB (Ethernet)

10:13:44.354565 IP > UDP, length 66

10:13:54.357000 IP > UDP, length 66

10:14:04.359866 IP > UDP, length 66

10:14:14.363731 IP > UDP, length 66


7. The final step is to ssh into vCenter and enable the shell and run this command

tcpdump -i eth0 -n “udp and port 902 and host”


tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes

10:31:38.067986 IP > UDP, length 66

10:31:48.070474 IP > UDP, length 66

10:31:58.076626 IP > UDP, length 66

10:32:08.075317 IP > UDP, length 66

10:32:18.077500 IP > UDP, length 66

Once you see that output in vCenter you can verify that vCenter is receiving heartbeats from the host.




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