vSAN Skyline Health alarm: vMotion: Basic (unicast) connectivity check and 'vMotion: MTU check (ping with large packet size)'
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vSAN Skyline Health alarm: vMotion: Basic (unicast) connectivity check and 'vMotion: MTU check (ping with large packet size)'

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Article ID: 398426

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Updated On:

Products

VMware vSAN

Issue/Introduction

  • In vCenter UI, Cluster > Monitor > vSAN > Skyline health shows Network alarm as below:

    vMotion: Basic (unicast) connectivity check and vMotion: MTU check (ping with large packet size)'



  • Click on the Troubleshoot option in the health warning will show the host which is unable to communicate with other hosts in the cluster.




  • Pings to the vMotion network of other hosts in the cluster will fail with 100% packet loss.

[Host-01:~] vmkping -I vmkX 192.168.##.## -S vmotion
PING 192.168.##.## (##.###.##.###): 56 data bytes

---  192.168.##.##  ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss

- where 'vmkX' is the vmkernel adaptor used for vMotion.

Environment

VMware vSAN (All Versions)

Cause

  • This issue could be caused due to an IP conflict of the vMotion IP with any other device in the environment.

  • From ESXi, var/run/log/vobd.log there is an event with "Duplicate IP address was detected"

    2026-03-17T09:24:07.915Z In(14) vobd[2098147]:  [netCorrelator] 64243210432us: [vob.net.vmknic.ip.duplicate] A duplicate IP address was detected for 10.146.xx.xx on interface vmk!. The current owner is 00:50:xx:xx:xx:xx.
    2026-03-17T09:24:07.915Z In(14) vobd[2098147]:  [netCorrelator] 64244312759us: [esx.problem.net.vmknic.ip.duplicate] Duplicate IP address detected for 10.146.xx.xx on interface vmk!, current owner being 00:50:xx:xx:xx:xx.
    2026-03-17T07:59:33.260Z In(14) vobd[2098147]:  [netCorrelator] 59169657973us: [esx.problem.net.vmknic.ip.duplicate] Duplicate IP address detected for 10.146.xx.xx on interface vmk!, current owner being 00:50:xx:xx:xx:xx.
    2026-03-17T08:01:51.502Z In(14) vobd[2098147]:  [netCorrelator] 59306882014us: [vob.net.vmknic.ip.duplicate] A duplicate IP address was detected for 10.146.xx.xx on interface vmk!. The current owner is 00:50:xx:xx:xx:xx.

  • /var/run/log/vmkernel.log reports that another device in the network have the same IP address of the VMkernel adaptor that is tagged for the vMotion traffic. It will also provide the MAC address of the other device.

YYYY-MM-DDTHH:MM:SS.###Z cpu78:2098609)Tcpip_Vmk: 124: arp: aa:bb:cc:dd:ee:ff is using my IP address 192.168.xx.xx on vmkX!
YYYY-MM-DDTHH:MM:SS.###Z cpu78:2098609)Tcpip_Vmk: 124: arp: aa:bb:cc:dd:ee:ff is using my IP address 192.168.xx.xx on vmkX!
YYYY-MM-DDTHH:MM:SS.###Z cpu78:2098609)Tcpip_Vmk: 124: arp: aa:bb:cc:dd:ee:ff is using my IP address 192.168.xx.xx on vmkX!
YYYY-MM-DDTHH:MM:SS.###Z cpu78:2098609)Tcpip_Vmk: 124: arp: aa:bb:cc:dd:ee:ff is using my IP address 192.168.xx.xx on vmkX!
YYYY-MM-DDTHH:MM:SS.###Z cpu78:2098609)Tcpip_Vmk: 124: arp: aa:bb:cc:dd:ee:ff is using my IP address 192.168.xx.xx on vmkX!

Resolution

 Engage the network team to further investigate the duplicate IP conflict issues.

Additional Information

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