IPv6 Solicited-node question

oudmasteroudmaster ✭
in CCIE Routing & Switching Technical

hi,

 

we have to let a
unicast address join multicast address and then calculate DMAC address. Why the
DMAC is not calculated directly from the unicast address?

 

thanks

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Comments

  • cristian.mateicristian.matei ✭

    Solicited-node is a multicast address computed as follows: it takes the last 24 bits of the unicast address and appends it to the prefix ff02::1:ff00:0/104. How can you calculate the DMAC from the unicast address? It's not always that the unicast address host portion is derived from the MAC address.

     

     

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  • oudmasteroudmaster ✭

    Hi Cristian,

     

    assume if the unicast of the remote IPv6 node is 2001:DB8::AB:1/64

    then its MAC address will be 33-33-FF-AB-00-01

    so this MAC will be used for its L2 address. everytime a host wants to communicate with this IP, it will use this L2 address.

    and this can be applied to all IPv6 unicast addresses assigned to the interface.

    so here I do not see a reason of converting the unicast address to multicast and then derive the MAC from it.  

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