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

Gert Doering <gert@space.net> Sat, 14 November 2015 18:50 UTC

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Date: Sat, 14 Nov 2015 19:50:52 +0100
From: Gert Doering <gert@space.net>
To: "Hemant Singh \(shemant\)" <shemant@cisco.com>
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Subject: Re: [v6ops] DAD again [was: draft-ietf-v6ops-host-addr-availability discussion]
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Hi,

On Sat, Nov 14, 2015 at 06:48:06PM +0000, Hemant Singh (shemant) wrote:
> >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, 

Right...

> 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.   

Also right.

But: the outbound interface will NOT use the lo0 source address for the ND
activity.  It will use the *interface* IP for ND, and the link-local one
for that.

There is no difference for the router between "send out a packet with a 
lo0 source to lan" and "send out a packet sourced by someone else to lan",
as far as ND activity on the LAN activity is concerned.

Surely you're not asking for a router to do DAD for every single IPv6
address that could be coming *through* that router?

> 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.

"the global address of the outbound interface" is NOT the lo0 source address.

Gert Doering
        -- NetMaster
-- 
have you enabled IPv6 on something today...?

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