« Two gateway machines, use keepalive.

The IPv6 address display:

inet6 x:x:x:x::1/64 scope global tentative dadfailed

and can't ping6 this address.

The reason is when another master machine is down, but the ipv6 address is not delete, and the new master machine can't use this address.

To prevent this: [...] sysctl -w net.ipv6.conf.$IFACE.accept_dad=0 »