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Connection Forcibly Closed by Remote Host

KB ID: 1781
Product: Veeam Backup & Replication
Published: 2013-07-05
Last Modified: 2025-09-25
Languages: JP | FR | ES
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Challenge

While a job is processing, a job may intermittently fail while sending data from the source proxy to the target proxy/repository server with:

srv| ERR |Server session thread has failed.
srv| >>  |An existing connection was forcibly closed by the remote host

Cause

This is related to a networking issue between the servers. These errors are most common when going across a WAN network. However, they can occasionally happen to local traffic as well.

Solution

Typically this issue is related to packet loss somewhere on the network between the two servers. There are some utilities to test the line, it is advisable to involve the ISP or networking team.

Some common tools typically recommended for testing are Iperf as it can give quite a bit of information about the network connection and Wireshark.

More Information

If the "forcibly closed by the remote host" error occurs consistently, a full investigation of the network instability is suggested as documented in the Solution section above. However, if the error only occurs occasionally, it is possible to adjust the number of reconnect attempts the agent processes perform. To do so, create the following registry value on the Veeam Backup server:

Key Location: HKLM\SOFTWARE\Veeam\Veeam Backup and Replication\
Value Name: AgentMaxReconnectRetries
Value Type: DWORD (32-bit) Value
Value Data (Default): 30

The default is 30 retries. This may be increased as needed.

Applying Custom Settings to Veeam Software Appliance
This article contains a registry value to adjust a setting within Veeam Backup & Replication on Windows. For information on applying custom settings to the Linux-based Veeam Software Appliance, review: KB4779: Applying Custom Settings to Veeam Software Appliance.

If this KB article did not resolve your issue or you need further assistance with Veeam software, please create a Veeam Support Case.

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