Re: DAD failure for global IPv6 addresses?

[Suresh Krishnan <suresh.krishnan at ericsson.com>]

Hi Peter,
  There are really two questions hidden in your question.

Peter.Hunt at nokia.com wrote:
> All,
>  
> I have a question about what the correct behaviour should be for a 
> router if a global address fails DAD.
>  
> Specifically, if an interface has a link-local address which passes DAD, 
> but also has a global address configured which is not based on the 
> hardware address, and which fails DAD, what packets should be allowed 
> in/out of the interface?

If the global address fails DAD, it should not be configured on the 
interface. i.e. The only IPv6 address configured on the interface will 
be the link local address.

>  
> Should the system behave exactly as though the global address was 
> absent? That is, should the router forward packets to or from the failed 
> address/network based on whatever routes exist in the forwarding table?

Routing and forwarding decisions are completely independent of what 
addresses are configured on the interface. Contrary to IPv4 behavior, 
the configuration of an address using P::/64 prefix does not 
automatically add a route to the P::/64 prefix. What prefixes are 
on-link is determined by

a) on a router - by configuration
b) on a host - by information contained in the RAs

This means that you can add a route pointing to the right interface for 
the P::/64 prefix even if DAD failed for an address configured using 
this prefix on the same interface.

Cheers
Suresh

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