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Non-TCP connections get disconnected whenever an IPsec tunnel comes up/down (UDP, VoIP)

mpachmann
#1 · 3. April 2025, 10:01

https://support.sophos.com/support/s/article/KBA-000008802?language=en_US

Issue

Non-TCP connections get disconnected whenever an IPsec tunnel, either site-to-site or remote access VPN, comes up/down. This affects RDP, VoIP, and other non-TCP connections.

Product and Environment

Sophos Firewall - All supported versions

Symptom

  • RDP in other Sophos Connect users experience a re-connect whenever a Sophos Connect user signs out.
  • VoIP phones get disconnected.
  • SSL VPN is disrupted.

Cause

All non-TCP connections on the VPN and WAN zones are deleted by design during an IPsec tunnel up/down event. This will cause existing non-TCP connections to be disconnected.

Resolution

As a workaround, do any of the following to make non-TCP applications or connections stable:

  • Make sure all applications running over IPsec VPN connections are TCP only.
  • Turn off the default disconnection behavior on Sophos Firewall:
    1. Access your Sophos Firewall console.
    2. Select Device Console and run the following command:

      set vpn conn-remove-tunnel-up disable

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