Re: [v6ops] DAD again [was: draft-ietf-v6ops-host-addr-availability discussion]

Owen DeLong <> Sun, 15 November 2015 00:59 UTC

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From: Owen DeLong <>
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Date: Sat, 14 Nov 2015 16:57:34 -0800
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To: "Hemant Singh (shemant)" <>
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Subject: Re: [v6ops] DAD again [was: draft-ietf-v6ops-host-addr-availability discussion]
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> On Nov 14, 2015, at 10:48 , Hemant Singh (shemant) <> wrote:
> -----Original Message-----
> From: Gert Doering [] 
> Sent: Saturday, November 14, 2015 1:13 PM
> To: Hemant Singh (shemant)
> Cc: Owen DeLong;
> Subject: Re: [v6ops] DAD again [was: draft-ietf-v6ops-host-addr-availability discussion]
>> This, actually, is a totally meaningless example.
> Not it's not since Owen ask that the lo interface is not in the same subnet at the outbound interface, so how is data forwarding working with ND if an address resolution is needed?  I proved data forwarding works.  I sure could have added to the example a log of the ND address resolution but any ND log is very copious due to NUD and thus I skipped the ND log. 

I didn’t say you couldn’t bridge the LO and External interfaces… I said that short of doing that, having the same subnet on both interfaces is a misconfiguration.

You haven’t proven that the interfaces aren’t bridged (or effectively so), nor have you proven that they are actually on the same subnet. Ergo, it is, actually, still a meaningless example.

>> I can send packets round the world with any source address I choose, and it has no significance for on-link NS or DAD with the *on-link* address of intermediate network segments.
>> If you look more closely at your box, you'll see that it will not use the
>> 2004::1 source address for ND on the next-hop lan interface.
> Correct.   This is what my point to Owen was.   The lo interface IPv6 address can be used to source packets out the router, and if the outbound interface has an incomplete or nonexistent entry in the neighbor cache, the outbound interfaces issues a ND address resolution and if the address resolution is completed, the packet is forwarded out.   I did issue "clear ipv6 neigh" on my router to clear the neighbor cache to force a ND address resolution.  The ND address resolution NS can use the link-local address or the global address of the outbound interface for sourcing the NS.

Sure, but the reply packet either has to get routed on the return (router has to somehow be a next hop for the LO prefix) or the router has to be incorrectly answering ND packets for the LO interface received on a different interface.