3com 4210 PWR 9-Port 3CR17341-91-ME User Manual

Where, FF02:0:0:0:0:1:FF is permanent and consists of 104 bits, and XX:XXXX is 
the last 24 bits of an IPv6 address.

Interface identifiers in IPv6 unicast addresses are used to identify interfaces on a 
link and they are required to be unique on that link. Interface identifiers in IPv6 
unicast addresses are currently required to be 64 bits long. An interface identifier is 
derived from the link-layer address of that interface. Interface identifiers in IPv6 
addresses are 64 bits long, while MAC addresses are 48 bits long. Therefore, the 
hexadecimal number FFFE needs to be inserted in the middle of MAC addresses 
(behind the 24 high-order bits).To ensure the interface identifier obtained from a 
MAC address is unique, it is necessary to set the universal/local (U/L) bit (the 
seventh high-order bit) to "1". Thus, an interface identifier in EUI-64 format is 
obtained.

Figure 190   Convert a MAC address into an EUI-64 address

The IPv6 neighbor discovery protocol (NDP) uses five types of ICMPv6 messages to 
implement the following functions:

■

Address resolution

■

Neighbor unreachability detection

■

Duplicate address detection

■

Router/prefix discovery

■

Address autoconfiguration

■

Redirection

Table 385 lists the types and functions of ICMPv6 messages used by the NDP.

                00000000 00010010 00110100 00000000 10101011 11001101

00000000 00010010 00110100 11111111 11111110 00000000 10101011 11001101

0012-3400-ABCD

00000010 00010010 00110100 11111111 11111110 00000000 10101011 11001101

0212:34FF:FE00:ABCD

MAC address:

Represented in binary:

Insert FFFE



Set U/L  bit:

EUI-64 address:

Table 385   Types and functions of ICMPv6 messages

Neighbor solicitation (NS) 
message 

Used to acquire the link-layer address of a neighbor 

Used to verify whether the neighbor is reachable 

Used to perform a duplicate address detection