For resolving above error or enabling IPv6 find below steps:
1. Confirm above error, restart/start ip6tables service
# service ip6tables restart
Unloading ip6tables modules: [ OK ]
Applying ip6tables firewall rules: ip6tables-restore v1.3.5: ip6tables-restore: unable to initializetable 'filter'
Error occurred at line: 2
Try `ip6tables-restore -h' or 'ip6tables-restore --help' for more information.
[FAILED]
2. Check /etc/modprobe.conf for below parameter:
alias ipv6 off
options ipv6 disable=1
3. Remove above parameters from modprobe.conf file
4. Restart machine.
5. Now restart/start ip6tables service
# service ip6tables restart
Flushing firewall rules: [ OK ]
Setting chains to policy ACCEPT: filter [ OK ]
Unloading ip6tables modules: [ OK ]
Applying ip6tables firewall rules: [ OK ]
