Hermant, thanks very much for your reply. To answer your questions, I am talking about a network interface on a router where the interface fails DAD for a global IPv6 address. "DAD failure" means that the interface received an NA or a DAD NS for the tentative global address, signalling a duplicate on another system on that link. I understand that the global address is not assigned to the interface, but I'm really asking about the implications of that on the behaviour of the router. The RFC states that the failure of a link-local address causes all IPv6 traffic to/from that interface to be dropped, and this led me to wonder about the effect of a global address DAD failure on traffic. >From the RFC excerpt you gave, I would infer that on DAD failure of a global >address, the router doesn't install the address, and forwards all traffic >to/from that network based on the contents of its forwarding table. It does no >special filtering of packets that are sourced from or destined to that network. Do you agree? Thanks, Peter
________________________________ From: ext Hemant Singh (shemant) [mailto:shem...@cisco.com] Sent: Thu 1/1/2009 6:57 PM To: Hunt Peter (Nokia-S&S/MtView); ipv6@ietf.org Subject: RE: DAD failure for global IPv6 addresses? Sorry, your email sounds a little confusing to me. Specifically, are you talking about a network interface on a router where the interface fails DAD during acquiring a global IPv6 address? Or are you talking about a node (potentially a host) in an IPv6 routed network where a network interface on the node failed DAD for a global IPv6 address? Also, I take it when you say "DAD failed", you mean the sending interface of the DAD has received an NA signaling a duplicate for the global address? If a duplicate for a global address is found in the network, then the network interface that send the DAD should not use the global IPv6 address to source any packets that need a global address for source. See text like the following snipped from section 5.4 of RFC 4861 [The procedure for detecting duplicate addresses uses Neighbor Solicitation and Advertisement messages as described below. If a duplicate address is discovered during the procedure, the address cannot be assigned to the interface. ] Nowhere does the text above differentiate between a link-local or a global address, so the rule applies to a global address a well. Happy New Year to everyone on this mailer. Hemant
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