Initial sync of VM replication stays stuck at 0%

Products

• VMware vSphere ESXi

Issue/Introduction

VM successfully configures for replication using vSphere Replication but does not progress and stays at 0%.

* /var/run/log/mkernel.log of Source ESXi reports connection timeout:

2025-01-28T06:29:02.855Z cpu83:7145151)Hbr: 2540: Wire compression supported by server X.X.X.X: FastLZ
2025-01-28T06:29:02.881Z cpu83:7145151)Hbr: 6591: Got requirements from server = 0x0
2025-01-28T06:29:04.936Z cpu57:5067735)Admission failure in path: host/user/vm.5067686:vmmanon.5067686
2025-01-28T06:29:04.936Z cpu57:5067735)vmmanon.5067686 (14371876) extraMin/extraFromParent: 476/476, vm.5067686 (14371833) childEmin/eMinLimit: 65816/66048
2025-01-28T06:29:04.936Z cpu57:5067735)Admission failure in path: host/user/vm.5067686:vmmanon.5067686
2025-01-28T06:29:04.936Z cpu57:5067735)vmmanon.5067686 (14371876) extraMin/extraFromParent: 476/476, vm.5067686 (14371833) childEmin/eMinLimit: 65816/66048
2025-01-28T06:29:13.912Z cpu83:7145151)WARNING: Hbr: 893: Failed to receive from X.X.X.X (groupID=GID-33ddc40e-4145-4e7d-8640-122c7c2a47d1): Timeout

(Note : In above logs X.X.X.X is the Target VR nic for replication traffic)

* /var/log/vmware/hbrsrv.log on Target VR also points an issue to network problem:

2025-01-28T12:16:30.108+05:30 verbose hbrsrv[2748298] [Originator@6876 sub=PropertyProvider] RecordOp ASSIGN: serverStats, HbrServer. Applied change to temp map.
2025-01-28T12:16:32.365+05:30 info hbrsrv[2748277] [Originator@6876 sub=Delta] ClientConnection (ClientCnx '[Y.Y.Y.Y]:55936' id=3 <shut>) is stopping ...
2025-01-28T12:16:32.365+05:30 info hbrsrv[2748277] [Originator@6876 sub=Asio] Closing LWD ASIO  ->  (plain text)
2025-01-28T12:16:32.365+05:30 info hbrsrv[2748277] [Originator@6876 sub=Delta] HbrSrv cleaning out ClientConnection ([Y.Y.Y.Y]:55936)
2025-01-28T12:16:32.365+05:30 error hbrsrv[2748277] [Originator@6876 sub=Main] HbrError stack:
2025-01-28T12:16:32.365+05:30 error hbrsrv[2748277] [Originator@6876 sub=Main]    [0] ClientConnection (client=[Y.Y.Y.Y]:55936) request callback failed: Connection reset by peer: The connection is terminated by the remote end with a reset packet. Usually, this is a sign of a network problem,  timeout, or service overload.
2025-01-28T12:16:32.365+05:30 error hbrsrv[2748277] [Originator@6876 sub=Main]    [1] Dropping error encountered from network

(Note : In above logs Y.Y.Y.Y is the Source ESXi vmkernel where replication traffic is enabled)

Environment

vSphere Replication 8.x
vSphere Replication 9.x

Cause

Network connection issue between the sites outside of ESXi hosts and Target VR. i.e. Firewall blocking the traffic, Physical switch level configuration disallowing traffic on port 31031

Resolution

Check the physical networking between sites to ensure Source ESXi traffic is allowed to Target VR.