It is imperative that the link local address of a node be unique. DAD is the process of ensuring that it is, indeed, unique. There are numerous ways in which the MAC address may not be unique, either through error or by local administrative efforts. In fact, in your example, you used a locally administered MAC address, for which there is no guarantee of uniqueness. I once worked for a hardware company, where I specified the MAC address in the SROM should be unique, using the eui-48 address process, and then used an example of 00:12:34:56:78:9a for the SROM programming, and they released hundreds of boards all with the same MAC address of 00:12:34:56:78:9a. So it happens. There are still manufactures who don't bother to get an OUI.
The IPV6 standard does allow for addresses formed from the eui-64 suffix and an advertised prefix to bypass DAD, provided the link-local address formed from the same suffix has passed DAD. In that case, the onus is on the router administrator to ensure that global address prefixes are properly formed. Mark Huth [EMAIL PROTECTED] wrote: > Hello > > I have got some basic questions regarding the need to perform DAD and a > confirmation would be appreciated > > Obviously DAD is performed to check the uniqueness of the auto-configured > data, but since the auto-configured address is formed by appending the prefix > advertised by RA with the MAC address of the interface, and since MAC > addresses are globally unique then why perfom DAD? > > For example when a MN moves to a visit net, then if for example if the MAC > address is AA:BB:CC:DD:EE:FF and the advertised prefix was 2001:001b::1/64 > then the newly autoconfigured address would be > 2001:001b:0:1:AABB:CCFF:FEDD:EEFF. > Am I correct? If i am then under what circumstances can this address have a > conflict with any other node on the new link as the MAC address is globally > unique??? > > A reply is eagerly awaited > > ZFaqeer > > > > > _________________________________________________________________ > Local listings, incredible imagery, and driving directions - all in one > place! Find it! > http://maps.live.com/?wip=69&FORM=MGAC01 > _______________________________________________ > mipl mailing list > [email protected] > http://www.mobile-ipv6.org/cgi-bin/mailman/listinfo/mipl > _______________________________________________ mipl mailing list [email protected] http://www.mobile-ipv6.org/cgi-bin/mailman/listinfo/mipl
