Routing Theory
IPv6 Addressing
IPv6 Addressing
  • Introduction
  • Addresses
  • Addressing Model
    • GUA
    • Link Local
    • Site Local
    • ULA
    • Anycast
    • Multicast
      • Solicited Node Multicast Address
  • Subnetting
    • Example
  • The last 64 bits
  • Routing Protocols
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  1. Addressing Model
  2. Multicast

Solicited Node Multicast Address

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Last updated 1 year ago

In IPv4, discovery at layer 2 takes pace by means of address resolution protocol or ARP. An Ethernet frame is broadcast with the source address of the node doing discovery and the destination address FF:FF:FF:FF:FF:FF

In IPv6 a Solicited Node Multicast Address is used by Neighbour Discovery Protocol (NDP) to discover the MAC address of an IPv6 address, the process is called DAD (Duplicate Address Detection).

The targeted host responds with a neighbour advertisement.

Setting up IPv6 may still be inconsistent and require some hidden switches. Once IPv6 is enabled on a router the command 

sh ipv6 int vlan 1

shows a default configuration and the neighbour discovery addresses.

Router10#sh ipv6 int vlan 1
Vlan1 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::21E:49FF:FE6B:E3C0
  No Virtual link-local address(es):
  No global unicast address is configured
  Joined group address(es):
    FF02::1
    FF02::1:FF6B:E3C0
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ICMP unreachables are sent
  Output features: Check hwidb
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds (using 33248)

Note that the last 6 hexadecimal characters (6B:E3C0) are a consistent across the link local address and the solicited node multicast group address and before that are the values FF:FE. These are EUI-64 generated addresses, I'll explain EUI-64 later.