Comment # 21 on bug 1171770 from Francisco Freitas

(In reply to Richard Brown from comment #19)
> No need for an ISO, found what I believe to be the trigger for the problem.
> 
> WORKAROUND:
> 
> Delete /etc/sysctl.d/70-yast.conf
> 
> If cluster is already bootstrapped, reboot all nodes. Cluster communications
> work properly afterwards.
> 
> NEXT STEP:
> 
> Figure out why the heck /etc/sysctl.d/70-yast.conf's blocking of IP
> forwarding is taking an effect when /usr/lib/sysctl.d/90-yast.conf should be
> overriding it :)

Nice ! I will try it out tonight.
Thanks for the workaround.