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

Products

• VMware vSphere ESXi

Issue/Introduction

• ESXi host alert : vSphere HA agent on host cannot reach some management network addresses of other hosts
  
  
  
  
• vSphere HA Agent report Error : Cannot Reach Management Network Addresses. 
  
  
• Following entries are reported in the hosts /var/run/log/fdm.log 

YYYY-MM-DDT07:14:36.617Z In(166) Fdm[3508814]: [Originator@6876 sub=Monitor opID=pingableAddressMonitor. cpp: 115-55318fe8]No ping reply from OtherHostIP
YYYY-MM-DDT07:14:36.6172 Db (167) [Originator@687sub=FDM opID=WorkQueue-3a450341] New event: EventEx=com.vmware.vc.HA.NotAllHostAddrsPingable vm=host=host-30##### tag=host-30##### : 1285265540:2
  
  
  
  
• Ping test will fail between the ESXi hosts on management IP.

Environment

VMware vSphere 8.x

VCF 9.0

Cause

• This issue occurs when an ESXi host involved in a vSphere HA event is unable to establish connectivity with the HA Master or other peer hosts in the cluster. This failure is typically detected when the host cannot ping the Management Network IP addresses of its peers.
• Common root causes include:
  
  • Firewall restrictions blocking the required bidirectional communication on ports 8182 TCP and UDP.
  • Misconfigured or incorrect Management Network IP settings on one or more hosts.
  • Inconsistent IPv6 configurations causing reachability failures.
  • General physical network connectivity issues or intermittent ping loss between ESXi management interfaces.

Resolution

To resolve this alert, ensure that all ESXi hosts in the cluster maintain consistent network connectivity for vSphere HA heartbeats.

• Verify Port Connectivity: Confirm that TCP and UDP port 8182 are open for bidirectional communication between all ESXi hosts in the cluster. For comprehensive details, refer to Port requirements for VMware vSphere ESXi.
• Network Validation: Collaborate with your internal network team to verify that ping tests are successful between the affected hosts on the Management IP network.
• Log Verification: Review the host's fdm.log located at /var/run/log for entries such as No ping reply from OtherHostIP to identify the specific peer hosts that are unreachable.