OPNsense disable IPv6

If the open source firewall OPNsense is to be used exclusively with IPv4, it is recommended to deactivate IPv6. To do this, perform the following steps (tested with OPNsense 25.1):

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  Dashboard view
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  Under Interfaces ‣ [WAN] set the IPv6 Configuration Type to None.
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  Then click on Save.
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  Click on Apply changes.
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  Under Interfaces ‣ [LAN], set IPv6 Configuration Type to None and click Save.
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  Then click on Save.
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  Click on Apply changes.
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  The change has been applied.
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  Under Firewall ‣ Rules ‣ LAN remove the IPv6 rule.
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  Confirm with Yes.
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  Click on Apply changes.
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  The change has been applied.
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  Under Interfaces ‣ Settings deactivate the Allow IPv6 option.
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  Then click on Save.
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  The change has been applied.
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  Dashboard view no longer shows an error.

References

Author: Werner Fischer Werner Fischer, working in the Knowledge Transfer team at Thomas-Krenn, completed his studies of Computer and Media Security at FH Hagenberg in Austria. He is a regular speaker at many conferences like LinuxTag, OSMC, OSDC, LinuxCon, and author for various IT magazines. In his spare time he enjoys playing the piano and training for a good result at the annual Linz marathon relay.