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1118 Views 10 Replies Latest reply: Feb 15, 2012 11:19 AM by Joshua Johnson - CCNP R&S RSS

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ipv6 is stalled

Feb 14, 2012 12:36 PM

Neuvin 14 posts since
Jun 12, 2011

Hi guys,

spend 45 mins troubleshooting a very basic ipv6 network untill i found that the serial0/0 'ipv6 is stalled'

 

i did a shut /no shut and even changed the mac-address on the interface hoping that this will chnage the link-local address of the interface.Nothing happened.

I read that i could also  use 'nd dad attempts x '

i tried this but still nothing.

can any1 help?

many thanks

Neuvin

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  • Beau Yancy 148 posts since
    Dec 10, 2010
    Currently Being Moderated
    1. Feb 14, 2012 2:13 PM (in response to Neuvin)
    Re: ipv6 is stalled

    Hi Neuvin,

     

    The serial interfaces don't have mac address so even if you configure it to have one, the router won't use it to make the IPv6 link local address. The router uses another method that should allow both links to still come up with unique link local address. Are you using GNS3 or real equipment?

     

    Regardless, I suggest you just manually configure the link local address for the interfaces.

     

    - Beau

  • Elvin Arias 1,855 posts since
    Mar 12, 2010
    Currently Being Moderated
    2. Feb 14, 2012 5:49 PM (in response to Neuvin)
    Re: ipv6 is stalled

    As Beau said serial interfaces doesn't have MAC addresses, so how configure itself the link-local address? They do it by taking into account the MAC address of the Ethernet interface. That would no cause any problems until i know, since as it's name state it's a link-local address, so would be LOCAL for that link. I recommend you to see this post. https://learningnetwork.cisco.com/message/202659#202659

     

    Post any doubt,

     

    Elvin

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,398 posts since
    Oct 7, 2008
    Currently Being Moderated
    3. Feb 14, 2012 8:34 PM (in response to Elvin Arias)
    Re: ipv6 is stalled

    Serial links will inherit a link-local from other interfaces...

     

    Otherwise, "ipv6 address fe80::1111 link-local" will do just fine.

     

    Scott

  • Elvin Arias 1,855 posts since
    Mar 12, 2010
    Currently Being Moderated
    5. Feb 15, 2012 7:18 AM (in response to Neuvin)
    Re: ipv6 is stalled

    Because serial interfaces doesn't have any MAC addresses as you may think, so the need to have some link-local addressing on the interface, for that reason the interface normally (by my experience) inherit the EUI-64 from the Ethernet interface, normally the lower numerical value.

     

    Elvin

  • Beau Yancy 148 posts since
    Dec 10, 2010
    Currently Being Moderated
    6. Feb 15, 2012 8:18 AM (in response to Neuvin)
    Re: ipv6 is stalled

    Just some more cosigning here...

     

    But, like we said, serial interfaces don't have mac addresses so they must get a mac address from somewhere! You would think that if you manually configure a mac address on the interface it would use that but it WON"T. Cisco documentation says it will use the first mac address in the routers pool of mac addresses. It seems that the first mac address in that pool is the lowest numbered ethernet interface (As Elvin said!)

     

    I think it is good practice to manually configure the link local address. Scott mentioned on another post that he would configure all link local addresses on a single device to be the same (since they are link local and won't conflict). For instance, it could be beneficial if you are trouble shooting a link to R5 and you know without checking that the link local is always FE80::5555 because you configured your network in that way.

     

    - Beau

  • Joshua Johnson - CCNP R&S 5,213 posts since
    Sep 22, 2009
    Currently Being Moderated
    7. Feb 15, 2012 8:40 AM (in response to Beau Yancy)
    Re: ipv6 is stalled

    You may want to use FE9, FEA, or FEB to make it obvious that it's manually configured?  Just a thought...

  • Joshua Johnson - CCNP R&S 5,213 posts since
    Sep 22, 2009
    Currently Being Moderated
    Re: ipv6 is stalled

    I guess it wouldn't matter as 5555 is pretty obvious as it is...

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,398 posts since
    Oct 7, 2008
    Currently Being Moderated
    Re: ipv6 is stalled

    Yeah...  And I had to stare at your last post for a minute because I was trying to figure out how you got from 5555 to FE9, FEA and FEB.     But then the Mt. Dew kicked in...   heheheheh.

     

    But yes, and another thing people do a lot is to imbed the IPv4 management address of a device in the link-local.  That way it is not only obvious, but also means something to you!

     

    While FE80::1 makes perfect sense in a lab for R1, that doesn't really scale well in the real world!

     

    Scott

  • Joshua Johnson - CCNP R&S 5,213 posts since
    Sep 22, 2009
    Currently Being Moderated
    Re: ipv6 is stalled

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