Re: 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 <[email protected]> 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 <[email protected] <mailto:[email protected] 
> >> 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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>
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