Re: IPv6 Anycast

Oops, reverse that. It sends an NA when it is anycast!

On Fri, Oct 9, 2009 at 11:41 AM, Bryan Bartik <bbartik_at_ipexpert.com> wrote:

> Nathan,
>
> I think it turns of IPv6 DAD detection for that address. Run "debug ipv6
> nd" when you enable a unicast address and an anycast address. When you have
> an anycast address, the router sends an NS instead of sendng an NA and
> waiting to see if it unique.
>
> R2(config-if)# ipv6 address 2002::2/64
>
> *Mar 1 03:36:55.771: ICMPv6-ND: Adding prefix 2002::2/64 to Serial1/1
> *Mar 1 03:36:55.775: ICMPv6-ND: Sending NS for 2002::2 on Serial1/1
> *Mar 1 03:36:56.779: ICMPv6-ND: DAD: 2002::2 is unique.
> *Mar 1 03:36:56.779: ICMPv6-ND: Sending NA for 2002::2 on Serial1/1
> *Mar 1 03:36:56.783: ICMPv6-ND: Address 2002::2/64 is up on Serial1/1
>
> R2(config-if)# ipv6 address 2003::2/64 any
>
> *Mar 1 03:37:06.471: ICMPv6-ND: Adding prefix 2003::2/64 to Serial1/1
> *Mar 1 03:37:06.471: ICMPv6-ND: Sending NA for 2003::2 on Serial1/1
> *Mar 1 03:37:06.475: ICMPv6-ND: Address 2003::2/64 is up on Serial1/1
>
>
>
> On Fri, Oct 9, 2009 at 9:34 AM, Nathan Richie <nathanr_at_boice.net> wrote:
>
>> So I understand the concept behind the Anycast feature of IPv6. But what
>> I am
>> failing to understand is the "anycast" option when configuring the ipv6
>> address.
>>
>> I assume it is so that the router is aware that the assigned address is an
>> Anycast address, but I fail to understand why the router needs to know
>> that.
>> I have read the documentation from Cisco Doc CD and all it says is:
>>
>> "Assigning a unicast address to more than one interface makes a unicast
>> address an anycast address. Nodes to which the anycast address is assigned
>> must be explicitly configured to recognize that the address is an anycast
>> address."
>>
>> Can anybody help me understand why the address must be recognized as an
>> Anycast?
>>
>> Thanks,
>>
>> Nathan Richie
>>
>>
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>>
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>
>
> --
> Bryan Bartik
> CCIE #23707 (R&S), CCNP
> Sr. Support Engineer - IPexpert, Inc.
> URL: http://www.IPexpert.com
>

-- 
Bryan Bartik
CCIE #23707 (R&S), CCNP
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com
Blogs and organic groups at http://www.ccie.net