A Kernel update on one box led to the following system error when trying to enable its IPv6-addresses again.
# /etc/init.d/network restart
Shutting down interface eth0: [ OK ]
Shutting down loopback interface: [ OK ]
FATAL: Module off not found.
CRITICAL : [ipv6_test] Kernel is not compiled with IPv6 support
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: FATAL: Module off not found.
CRITICAL : [ipv6_test] Kernel is not compiled with IPv6 support
[ OK ]
FATAL: Module off not found.
CRITICAL : [ipv6_test] Kernel is not compiled with IPv6 support
Which was odd, since its IPv6 addresses worked just fine before the reboot. Chances are, a change in /etc/modprobe.conf disabled IPv6. Here’s what may be in there.
# cat /etc/modprobe.conf alias eth0 e1000 alias scsi_hostadapter mptbase alias scsi_hostadapter1 mptspi alias scsi_hostadapter2 ata_piix alias net-pf-10 off alias ipv6 off options ipv6 disable=1
If you comment out those last 3 lines (that effectively disable IPv6) and reboot your box, you should have IPv6 connectivity again. Simply place a #-sign in front of them will suffice.