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Re: [VRRP] why link-local address for ipv6 VRRP

Hi,
The main reason why the link-local address is the first address is because link-local addresses are used extensively in IPv6 neighbor discovery. For example, a host's default route to a router will point to the link-local address, not a specific global address of the router. In order for the hosts traffic to switch over to a backup router the link-local router of the router must be used by VRRPv6.
If this isn't clear, I suggest that one go and re-read the IPv6 neighbor discovery and auto-configuration specifications to understand how IPv6 uses link-local addresses. One need to understand ND and Auto-config inorder to understand how VRRPv6 works. 

Regards,
Bob


On Jul 3, 2008, at 6:51 AM, G. C. wrote:
Ideally, the draft would describe this further. Currently, it not explicitly stated.
One use is for Router Advertisement - a virtual router would have to use the virtual link-local address as the source address. When a backup router transitions to master and starts sending out RAs, it too would need to use the same source IP address. 

Did someone see the need for this address for something else?

Cheers,
Georges

On Thu, Jul 3, 2008 at 1:27 AM, Huafeng Lu <Huafeng.Lv at sun.com> wrote:
G. C. ??:

Hi Huafeng,
Based on my understanding of the draft, we allow the configuration of global addresses too.
In the VRRP Advertisement packet, the draft states that the first address must be link-local. The other addresses can be global addresses. 

Regards,
Georges Chung
Thanks Georges. In other words, among the "IPvX addresses associated with the virtual router", at least one must be link-local, right? If so, why do we have to have a link-local virtual router address? (I think the all the "IPvX addresses associated with the virtual router" are the virtual addresses of the virtual router, and these virtual addresses are to be protected by VRRP, right?) 

Thanks.
--
Huafeng
On Wed, Jul 2, 2008 at 6:01 AM, Huafeng Lu <Huafeng.Lv at sun.com <mailto:Huafeng.Lv at sun.com >> wrote: 


   Hi, VRRPers,

   I'm new to this mail list...
While reading draft-ietf-vrrp-unified-spec-02, I found the virtual IPv6 
   address to be covered by the virtual router should be a link-local
   address. On the VRRP routers that compose the virtual router, the
addresses used to send VRRP advertisements are also link-local. Is there 
   a reason to require link-local addresses? What's the possibility of
   extending this to global addresses?

   Thanks.
   --
   Huafeng
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