Re: IPV6 Duplicate Address Detection(DAD)

Thank you and you all have great friday and weekend

Regards
Anantha Subramanian Natarajan

On Fri, Sep 18, 2009 at 9:47 AM, ALL From_NJ <all.from.nj_at_gmail.com> wrote:

> You rock man. Happy Friday and happy labbing!
>
>
>
> On Fri, Sep 18, 2009 at 10:11 AM, Anantha Subramanian Natarajan <
> anantha.natarajan_at_gravitant.com> wrote:
>
>> Hi Andrew,
>>
>> Thank you very much .....Totally missed the concept that the link-local
>> address doesn't have the /64 ...Thanks for highlighting the same
>> ......Tested and found out that,when the link local address has duplicate
>> address detection,the ipv6 interface would be stalled and that means no
>> processing of ipv6 on the interface but if the global addresses are detected
>> with duplicate address the interface will still process ipv6 .Please correct
>> me if my understanding is wrong .
>>
>> R1#sh ipv6 interface
>> FastEthernet0/0 is up, line protocol is up
>> *IPv6 is stalled,* link-local address is *FE80::1 [DUP]*
>>
>> Once again thank you very much andrew
>>
>> Regards
>> Anantha Subramanian Natarajan
>>
>>
>>
>>
>> On Fri, Sep 18, 2009 at 8:46 AM, ALL From_NJ <all.from.nj_at_gmail.com>wrote:
>>
>>> Ok cool. I would suggest to start over and clear your configs. For this
>>> testing, you do not need anything but a common segment between 2 routers.
>>>
>>> You might want to turn this on --> debug ipv6 nd (see a lot of output
>>> when you no shut the interface, great for learning)
>>>
>>> For the link local address, type this instead on both routers:
>>>
>>> interface xyz
>>> shut
>>> ipv6 add fe80::1 link-local
>>> no shut
>>>
>>> Once you add the same link local on both routers and type no shut, you
>>> will see the problem manifest itself.
>>>
>>> Notice the link local address does not have the concept of a /64 bit
>>> masks ... it is not global, but link local.
>>>
>>> HTH,
>>>
>>> Andrew
>>>
>>>
>>>
>>>
>>>
>>> On Fri, Sep 18, 2009 at 7:53 AM, Anantha Subramanian Natarajan <
>>> anantha.natarajan_at_gravitant.com> wrote:
>>>
>>>> Hi Andrew,
>>>>
>>>> Thank you very much for the time and the explanation.So you mean if
>>>> the link local address is been detected on a link having duplicate address
>>>> will not causes the interface to be in stalled (ipv6 processing
>>>> disabled).Very good info and thank you very much.
>>>>
>>>> I had chance to lab it with duplicate global address on the link and the
>>>> output showed as below which clarified my earlier question oh how to
>>>> differentiate DAD on link local or global ipv6 address.It seems if there is
>>>> a DAD with global ipv6 address,it will just indicate DUP as below and the
>>>> ipv6 interface will not have any issue as you mentioned which is logical as
>>>> there can be many global ipv6 addresses per link.
>>>>
>>>> FastEthernet0/0 is up, line protocol is up
>>>> IPv6 is enabled, link-local address is FE80::C001:16FF:FEC4:0
>>>> Global unicast address(es):
>>>> 2001::1, subnet is *2001::/64 [DUP]*
>>>> **
>>>> But I couldn't able to create Duplicate addresses for link-local ,I was
>>>> under impression that I would be able to create link local by using the
>>>> command ipv6 address FE80::1/64 link-local manually but while I type it ,it
>>>> didn't give me an option for link-local,I am using dynamips,I am sure
>>>> missing something.Kindly correct me .
>>>>
>>>> Andrew I am hoping that if the link-local has Duplicate address,the ipv6
>>>> interface should go into stalled state and thus no ipv6 processing.I just
>>>> want to reconfirm with you, that you created duplicate address for the link
>>>> local address but still that interface was up and working fine.Kinly let me
>>>> know
>>>>
>>>> Thank you very much for the help.
>>>>
>>>> Regards
>>>> Anantha Subramanian Natarajan
>>>>
>>>> * *
>>>>
>>>>
>>>> On Thu, Sep 17, 2009 at 11:01 PM, ALL From_NJ <all.from.nj_at_gmail.com>wrote:
>>>>
>>>>> Good evening team,
>>>>>
>>>>> Anantha, dup global addresses will not create any issues with the
>>>>> interface coming up or with the control protocol traffic. Team, ... keep me
>>>>> honest here. ;-)
>>>>>
>>>>> In a lab test I just did, I configured two routers on the same segment
>>>>> to have dup global addresses and unique link local. I then added some loops
>>>>> to one of these and configured OSPF on everything.
>>>>>
>>>>> I then configured IPv6 and OSPF on another router from another segment;
>>>>> one hop away. Since everything is associated with link local, there was not
>>>>> any problems with connectivity, routing updates and or pings. I could get
>>>>> to the loops on the correct router, and at first it appeared that dups did
>>>>> not matter much at all.
>>>>>
>>>>> Interesting to lab this out and understand where a routing loop can
>>>>> occur. Since clients get their addresses from DHCP or autoconfig, having
>>>>> dups in your network could cause two segments in different parts of the
>>>>> network to have an identity crisis / overlapping address space.
>>>>>
>>>>> Apart from this, no worries. Have a great night,
>>>>>
>>>>> Andrew
>>>>>
>>>>>
>>>>>
>>>>> On Thu, Sep 17, 2009 at 11:00 PM, Anantha Subramanian Natarajan <
>>>>> anantha.natarajan_at_gravitant.com> wrote:
>>>>>
>>>>>> Hi All,
>>>>>>
>>>>>> Would like to confirm about the IPV6 Duplicate Address
>>>>>> Detection(DAD), DAD
>>>>>> would detect duplicate addresses ,if exist for both link local address
>>>>>> and
>>>>>> global ipv6 unique address on a link.Is that right ?..If so,in the
>>>>>> below
>>>>>> show output,if it mentions ipv6 is stalled,I am understanding that a
>>>>>> duplicate link local address is been detected on the link and ipv6
>>>>>> processing on the interface is disabled.Please correct me if I am
>>>>>> wrong on
>>>>>> this.
>>>>>>
>>>>>> My question is ,if DAD detects duplicate address on the global ipv6
>>>>>> address
>>>>>> on the link,does that also will lead to stalled interface,if so,how we
>>>>>> can
>>>>>> distinguish between link local and global ipv6 duplicate address
>>>>>> detection.
>>>>>>
>>>>>> Kindly help me to understand the above.
>>>>>>
>>>>>> Router# show ipv6 interface ethernet 0
>>>>>> Ethernet0 is up, line protocol is up
>>>>>> *IPv6 is stalled*, link-local address is FE80::1
>>>>>>
>>>>>> Thank you very much for the help
>>>>>>
>>>>>> Regards
>>>>>> Anantha Subramanian Natarajan
>>>>>>
>>>>>>
>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>
>>>>>>
>>>>>> _______________________________________________________________________
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>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Andrew Lee Lissitz
>>>>> all.from.nj_at_gmail.com
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Andrew Lee Lissitz
>>> all.from.nj_at_gmail.com
>>>
>>
>>
>
>
> --
> Andrew Lee Lissitz
> all.from.nj_at_gmail.com

Blogs and organic groups at http://www.ccie.net
Received on Fri Sep 18 2009 - 09:50:36 ART