Department of Defense
High Performance Computing Modernization Program

Enabling IPv6 in OpenBSD UNIX

IPv6 has been enabled by default in OpenBSD for so long (since at least 3.0) that there is little point in describing how to enable it.

IPv6 privacy extensions were first supported in OpenBSD 4.8, and became enabled by default in OpenBSD 5.3.

To manually disable the use of IPv6 privacy extensions, determine the name of the installed network interfaces using the ifconfig command. Typical interfaces are em0 or fxp0.

To disable IPv6 privacy extensions on an inet6-enabled interface em0, execute the following:

ifconfig em0 –autoconfprivacy

The existing temporary privacy address will persist until it becomes invalid.

To enable IPv6 privacy extensions on an inet6-enabled interface em0, execute the following:

ifconfig em0 autoconfprivacy

A temporary privacy address will be generated and assigned to the interface em0. It will automatically be replaced by another temporary privacy address after 24 hours of use and after receipt of the next router advertisement for that interface’s prefix.

For more details, please look at the OpenBSD ifconfig manual page.

Disabling IPv6 in OpenBSD UNIX

The recommended practice is to block all IPv6 inbound and outbound traffic in the pf packet filter, rather than attempting to disable it in the kernel.

1. Edit the file /etc/pf.conf

2. Add the following lines to the end of the file

block in inet6

block out inet6

3. Reboot (or, restart the pf.d script)

For more details, please look at the OpenBSD pf manual page.


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