RHEL: When are IPv6 link local addresses assigned?

Issue

• We are seeing an issue where the IPv6 interface operations are behaving in an unexplained manner. As part of getting our nodes to perform IPv6 operations we configure link-local IPv6 addresses on them. The interface itself comes up with the MAC based link-local address as soon as it is brought up. What we also notice is that the address configured later is the address that becomes the primary address on the node and is used as the source address for any packets leaving the node using that interface.
• What we see is that on occasions at bootup the MAC based address becomes the primary link local address.