Since it’s the third time I’ve had to do this so far this year, I’m going to write down how I disable IPv6 in Fedora. Add these lines to /etc/sysctl.conf

[lisa@server~]# grep ipv6 /etc/sysctl.conf
net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
net.ipv6.conf.lo.disable_ipv6=1

Then load the sysctl settings (sysctl -p) or reboot.

Without IPv6, if you do X-redirection, you may get an error indicating the redirection was refused. In journalctl, there’s an error “error: Failed to allocate internet-domain X11 display socket”. Evidently you’ve got to configure sshd to use IPv4 by setting “AddressFamily inet” in /etc/ssh/sshd_config

[lisa@server~/]# grep AddressFamily /etc/ssh/sshd_config
AddressFamily inet