RE: Is Link-Local address mandatory for a host device?

["Hemant Singh (shemant)" <shemant at cisco.com>]

Erik Nordmark wrote:

>I suspect that you also can't use DHCPv6 for non-addresses (finding the

>DNS servers etc) since DHCPv6 might assume that some communication uses

>the link-local address. But I haven't checked in the RFC.

Snipped from RFC 3315, section 1.1 is:

[Clients and servers exchange DHCP messages using UDP [15].  The
 client uses a link-local address or addresses determined through
 other mechanisms for transmitting and receiving DHCP messages.]

Using link-local for DHCPv6 has the advantage that well-known mcast
addresses can be used for clients to communicate with the server or
relay agents.  RFC 3315 also mentions such an advantage in section 3. Of
course, even IPv6 mcast uses link-local address.  So really, it is not
wise for a host to not use a link-local address at all. 

Hemant