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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)
                9  Internet Protocol Version 6 (IPv6) / IP Next Generation (IPng)
                     9  IPv6 Addressing

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IPv6/IPv4 Address Embedding
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IPv6 Autoconfiguration and Renumbering
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IPv6 Multicast and Anycast Addressing
(Page 4 of 5)

Solicited-Node Multicast Addresses

In addition to the regular multicast addresses, each unicast address has a special multicast address called its solicited-node address. This address is created through a special mapping from the device’s unicast address. Solicited-node addresses are used by the IPv6 Neighbor Discovery (ND) protocol to provide more efficient address resolution than the ARP technique used in IPv4.

All solicited-node addresses have their T flag set to zero and a scope ID of 2, so they start with “FF02”. The 112-bit group ID is broken down as follows (see Figure 103):


Figure 103: IPv6 Solicited Node Address Calculation

The solicited node multicast address is calculated from a unicast address by taking the last 24 bits of the address and prepending them with the IPv6 partial address “FF02:0:0:0:0:1:FF”. This shows the example address from Figure 95 converted to its solicited node address, FF02::1:FFC8:1FFF.

 


  • 80 bits consisting of 79 zeroes followed by a single one; this means that in colon hexadecimal notation, the next five hexadecimal values are “0000:0000:0000:0000:0001”, or more succinctly, “0:0:0:0:1”.

  • 8 ones: “FF”.

  • 24 bits taken from the bottom 24 bits of its unicast address.

So, these addresses start with “FF02:0:0:0:0:1:FF” followed by the bottom 24 bits of the unicast address. So, the node with IP address 805B:2D9D:DC28:0:0:FC57:D4C8:1FFF would have a solicited-node address of FF02:0:0:0:0:1:FFC8:1FFF (or FF02::1:FFC8:1FFF).

Key Concept: Each unicast address has an equivalent solicited-node multicast address, which is created from the unicast address and used when other devices need to reach it on the local network.



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IPv6/IPv4 Address Embedding
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IPv6 Autoconfiguration and Renumbering
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