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379 Views 4 Replies Latest reply: May 7, 2012 11:30 PM by Scott Morris - CCDE/4xCCIE/2xJNCIE RSS

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Link Local Address IPv6

May 6, 2012 6:25 AM

ricardoglzs 23 posts since
Jan 17, 2011

Why someone want to change  the link local address, if the composition of this is automatically, there's risk to duplicate this address in the network if we changed  right?

I mean if the composition is with the EUI-64 in the last 64 bits in this way is perfect.

 

I'm initiating my studies in IPv6 but i do not catch why someone want to do this..

 

Thank you

  • Elvin Arias 1,855 posts since
    Mar 12, 2010
    Currently Being Moderated
    1. May 6, 2012 6:33 AM (in response to ricardoglzs)
    Re: Link Local Address IPv6

    If you want to have the total control of the LLA assigment you usually hardcode things. Technically you can have the same LLA on different interfaces in the same router and nothing bad happens, since it's a LLA, but sometimes administrators wants to have something more "meaningful" and, for example, assign the "FE80::1" LLA to "R1". That is in order to correlate things in your topology.

     

    Elvin

     

    Message was edited by: Elvin Arias

  • piperflyer 153 posts since
    Jan 21, 2009
    Currently Being Moderated
    2. May 6, 2012 7:17 AM (in response to ricardoglzs)
    Re: Link Local Address IPv6

    Its very useful to define the link local address as something simple, eg fe80::1 for frame relay mappings.  FR does not support inverse arp for IPV6 so all you link locals are going to have to be manually mapped.

  • Jeff 65 posts since
    Dec 4, 2010
    Currently Being Moderated
    3. May 7, 2012 8:04 PM (in response to ricardoglzs)
    Re: Link Local Address IPv6

    Arias is right,thats what link local means.Its significant in only 1 segment/subnet.You can treat the LLA like a hostname if you configure LLA like Arias did.here is my example:

    R5#show ipv route

    ***

    O   2001:4::/64 [110/2]

         via FE80::4, FastEthernet1/9

         via FE80::4, FastEthernet1/4

    ****

    I have R4 and R5 connecting each other with 2 interface,all with the same LLA to represent a nexthop route(R4 in this case).

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,397 posts since
    Oct 7, 2008
    Currently Being Moderated
    4. May 7, 2012 11:30 PM (in response to ricardoglzs)
    Re: Link Local Address IPv6

    Do you memorize your MAC addresses?  Most people don't.  So on key devices, it's better to hard-code.  That way when looking at things like a routing table, the values make sense to you!

     

    In a lab, I'd say this is critical for speed.

     

    Scott

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