B
ASIC
IP C
ONFIGURATION
36-19
• If a duplicate address is detected, a warning message is sent to the
console.
• IPv6 addresses are 16 bytes long, of which the bottom 8 bytes typically
form a unique host identifier based on the device’s MAC address. The
EUI-64 specification is designed for devices that use an extended
8-byte MAC address. For devices that still use a 6-byte MAC address
(also known as EUI-48 format), it must be converted into EUI-64
format by inverting the universal/local bit in the address and inserting
the hexadecimal number FFFE between the upper and lower three
bytes of the of the MAC address.
• For example, if a device had an EUI-48 address of
28-9F-18-1C-82-35, the global/local bit must first be inverted to meet
EUI-64 requirements (i.e., 1 for globally defined addresses and 0 for
locally defined addresses), changing 28 to 2A. Then the two bytes
FFFE are inserted between the OUI (i.e., company id) and the rest of
the address, resulting in a modified EUI-64 interface identifier of
2A-9F-18-FF-FE-1C-82-35.
• This host addressing method allows the same interface identifier to be
used on multiple IP interfaces of a single device, as long as those
interfaces are attached to different subnets.
Example
This example uses the general network prefix of 2001:0DB8:0:1::/64 used
in an earlier example, and specifies that the EUI-64 interface identifier be
used in the lower 64 bits of the address.
Console(config)#interface vlan 1
Console(config-if)#ipv6 address 2001:0DB8:0:1::/64 eui-64
Console(config-if)#end
Console#show ipv6 interface
Vlan 1 is up
IPv6 is enable.
Link-local address:
FE80::200:E8FF:FE90:0/64
Global unicast address(es):
2001:DB8::1:200:E8FF:FE90:0, subnet is 2001:DB8:0:1::/64
Joined group address(es):
FF01::1/16
FF02::1/16
FF02::1:FF90:0/104
MTU is 1500 bytes.
ND DAD is enabled, number of DAD attempts: 1.
ND retransmit interval is 1000 milliseconds
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