CLI Reference Guide-R02

Chapter 28 | IP Interface Commands
IPv6 Interface
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◆ 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 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 network prefix of 2001:0DB8:0:1::/64, 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 enabled
Link-local address:
fe80::7272:cfff:fe83:3466%1/64
Global unicast address(es):
2001:db8:0:1:7272:cfff:fe83:3466/64, subnet is 2001:db8:0:1::/64[EUI]
2001:db8:2222:7272::72/96, subnet is 2001:db8:2222:7272::/96
Joined group address(es):
ff02::1:ff00:72
ff02::1:ff83:3466
ff02::1
IPv6 link MTU is 1500 bytes
ND DAD is enabled, number of DAD attempts: 3.
ND retransmit interval is 1000 milliseconds
ND advertised retransmit interval is 0 milliseconds
ND reachable time is 30000 milliseconds
ND advertised reachable time is 0 milliseconds
ND advertised router lifetime is 1800 seconds
Console#
Related Commands
ipv6 address autoconfig (817)
show ipv6 interface (823)