This is the sequel post to the first part in which I mainly covered some elements of the specification wrt the “on-link” flag and the IPv6 subnet model.
In short each IPv6 address has an associated flag which determines if the host considers the respective address to be part of “a network where neighbors exist”. If this is the case ND is performed to talk to them, otherwise all communication with other hosts on that prefix is sent to the router. This flag is NOT set for DHCPv6 addresses (and, btw, just to make this clear already, there’s no way of setting it as part of the DHCP configuration procedure either) so communication with hosts with the same DHCPv6 provided prefix is supposed to go through a router, which in turn is very different (behavior) from the IPv4 world.
At the end of the first part we had a configuration state which led to two global addresses on both systems involved, a DHCPv6 provided one and another one generated as part of the SLAAC process, which can create operational issues of all kinds (improper source address selection, hindered troubleshooting etc.). Furthermore such a setting does not reflect “the operational DHCPv4 model” which we envisaged as the ultimate goal of our exercise. I had finished that post along the lines: “we then have to get rid of the SLAAC address”.
Continue reading “Router Advertisement Options to the Rescue – A Deep Dive into DHCPv6, Part 2”
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