Alarm "vSphere HA agent on host cannot reach some management network addresses of other hosts" observed for hosts.

Products

• VMware vSphere ESXi

Issue/Introduction

•  Intermittent ESXi host alert observed on single or multiple ESXi hosts :
  
  vSphere HA agent on host cannot reach some management network addresses of other hosts
  
  

 

• The alarm gets resolved on its own and keeps re-appearing multiple times.
• The following entries are reported in the HA  master host's log location :- /var/run/log/fdm.log:

YYYY-MM-DDT16:31:45.623Z Er(163) Fdm[2102256]: [Originator@6876 sub=Cluster opID=clusterManager.cpp:983-2ef0694e] Timeout for slave @ host-XXXX
YYYY-MM-DDT16:31:45.623Z Db(167) Fdm[2102256]: [Originator@6876 sub=Cluster opID=clusterManager.cpp:983-2ef0694e] Marking slave host-XXXX as unreachable

• The following log entries are reported on the affected ESXi host's /var/run/log/fdm.log

2026-04-26T16:28:02.662Z Db(167) Fdm[2102532]: [Originator@6876 sub=FDM opID=WorkQueue-######] New event: EventEx=com.vmware.vc.HA.NotAllHostAddrsPingable vm= host=host-#### tag=host-####:-#########:#####

Environment

VMware ESXi

Cause

• Due to the physical network instability, the ARP request sent by the ESXi host to its PEER host in HA cluster fails.
• If the ESXi host sends out an ARP request to find a peer host in the cluster and receives no reply, the ESXi host's internal ARP table entry for that peer will expire and turn "Incomplete."
• Without a valid ARP mapping (IP to MAC), the ESXi host cannot test the heartbeat across its PEER, causing the vSphere HA agent communication to break and triggering the alarm

Resolution

• To resolve this alert, collaborate with your physical network team to address the physical infrastructure instability.

 

Additional Information

To Analyze ARP and Latency

• Perform a packet capture on the affected ESXi host and filter for ARP traffic. Verify if there is a significant delay between the ARP Request (Who has IP X?) and the ARP Reply (IP X is at MAC Y).
• Please follow KB: Packet capture on ESXi using the pktcap-uw tool to perform packet captures in the affected ESXi host.
• Upload the packet capture file onto the case by following: Uploading files to cases on the Broadcom Support Portal to review the captures and check if the latency is from physical switch end. 

Refer to the article below for other HA related issue

ESXi host shows "vSphere HA agent on host cannot reach some management network addresses of other hosts" alert.