Enhanced Replication Mapping errors and replicated VMs remain in "Not Active" state due to MTU mismatch

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Enhanced Replication Mapping errors and replicated VMs remain in "Not Active" state due to MTU mismatch

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Article ID: 442123

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Updated On:

Products

VMware Live Recovery

Issue/Introduction

When configuring or testing Enhanced Replication mappings in VMware Live Recovery or vSphere Replication, the following symptoms may be observed:

The Enhanced Replication Mapping test remains stuck or fails to complete.
Replication status is reported as Not Active.
The SRM or vSphere Replication UI displays errors such as:
- Fault occurred while performing health check. Details: 'Connect: Connection reset by peer'
- Fault occurred while performing health check. Details: 'Connect: Input/output error'
The ESXi host logs contain the following entries:
- /var/run/log/hbrsrv.log: Dropping error encountered from network or ClientConnection request callback failed: Failed to read: End of file.
- /var/run/log/hbr-agent.log: SSL handshake failed: Connection reset by peer or Error writing response: Broken pipe.

Environment

VMware ESXi
VMware vSphere Replication
VMware Live Recovery

Cause

The issue is typically caused by inconsistent Maximum Transmission Unit (MTU) settings along the network path between the source and target ESXi hosts.

Enhanced Replication utilizes direct host-to-host communication over port 32032. If the replication VMkernel adapters are configured for Jumbo Frames (MTU 9000) but any intermediate physical device such as a switch, router, or WAN link, is configured for a smaller MTU (e.g., 1500), the larger data packets will be dropped. This results in TCP connection resets and prevents the replication health check from succeeding.

Resolution

To resolve this issue, ensure end-to-end MTU consistency for the replication traffic path.

1. Validate the Network Path (Bidirectionally)

Use the vmkping command from the ESXi CLI to verify if the network path supports the configured MTU.

Test Standard Frames (MTU 1500): Review this command before running it. vmkping -I vmk# -d -s 1472 [Target_ESXi_IP]
Test Jumbo Frames (MTU 9000): Review this command before running it. vmkping -I vmk# -d -s 8972 [Target_ESXi_IP]

If the 1472-byte ping succeeds but the 8972-byte ping fails, there is an MTU mismatch in the physical or virtual network path.

2. Align MTU Settings

Perform one of the following actions based on your network requirements:

Option A: Revert to Standard Frames Change the MTU to 1500 on the replication VMkernel adapters of all participating source and target ESXi hosts.
Option B: Fix Physical Network Configuration Engage your networking team to ensure that Jumbo Frames (MTU 9000) are enabled on all physical switch ports, routers, and WAN segments between the sites.