WB1 9.4 IPv6 EUI-64 Addressing

9.4 IPv6 EUI-64 Addressing

• Configure globally aggregatable IPv6 addresses in the format
2001:X:0:146::Y/64 on the VLAN 146 interfaces of R1, R4, and R6.
• Here X is your rack number in decimal notation, (e.g. 10 for Rack10, not
the hex 0A) and the router will automatically derive Y based on the
interface MAC address.

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R1:
interface FastEthernet 0/0
ipv6 address 2001:1:0:146::/64 eui-64

R4:
interface FastEthernet 0/1
ipv6 address 2001:1:0:146::/64 eui-64

R6:
interface FastEthernet 0/0.146
ipv6 address 2001:1:0:146::/64 eui-64

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Extended Unique Identifiers (EUIs) are 64-bit values assigned to physical
interfaces. EUI’s are similar in many respects to IEEE MAC addresses, in that
they identity a physical interface, but EUI’s are designed to be used universally,
not just with the hardware addresses.

IPv6 uses EUI-64 to construct a unique host address on a shared Ethernet
segment automatically. When you use the eui-64 keyword, the IOS uses the
48-bit hardware address of the Ethernet interface as the foundation to construct
the unique 64-bit Interface identifier of the IPv6 address.

Specifically this is accomplished by inverting the 7th most significant bit of the
Ethernet MAC address, called the Universal/Local (U/L) bit, and then inserting 16
bits of padding in the format FFFE in the middle.

From the above output we can see that the EUI-64 derived host address of R1’s
Fa0/0 interface is 20D:65FF:FE84:6560. This means that the MAC address of
R1’s Fa0/0 interface is 000D:6584:6560. Note that the link-local address of the
interface automatically uses the format FE80::[EUI-64] unless manually modified.

Rack1R1#show interfaces fastEthernet 0/0 | include add
  Hardware is Gt96k FE, address is c200.0b0c.0000 (bia c200.0b0c.0000)
  Internet address is 155.1.146.1/24
Rack1R1#
Rack1R1#
Rack1R1#show ipv6 interface fastEthernet 0/0         
FastEthernet0/0 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::C000:BFF:FE0C:0
  No Virtual link-local address(es):
  Global unicast address(es):
    2001:1:0:146:C000:BFF:FE0C:0, subnet is 2001:1:0:146::/64 [EUI]
  Joined group address(es):
    FF02::1
    FF02::1:FF0C:0
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ICMP unreachables are sent
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
Rack1R1#

Rack1R4#sh interfaces fastEthernet 0/1 | include address
  Hardware is Gt96k FE, address is c203.1230.0001 (bia c203.1230.0001)
  Internet address is 155.1.146.4/24
Rack1R4#                                               
Rack1R4#show ipv6 interface fa0/1                         
FastEthernet0/1 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::C003:12FF:FE30:1
  No Virtual link-local address(es):
  Global unicast address(es):
    2001:1:0:146:C003:12FF:FE30:1, subnet is 2001:1:0:146::/64 [EUI]
  Joined group address(es):
    FF02::1
    FF02::1:FF30:1
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ICMP unreachables are sent
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
Rack1R4#

Rack1R6#sh interfaces fastEthernet 0/0 | include address
  Hardware is Gt96k FE, address is c205.1230.0000 (bia c205.1230.0000)
Rack1R6#
Rack1R6#show ipv6 interface fa0/0.146
FastEthernet0/0.146 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::C005:12FF:FE30:0
  No Virtual link-local address(es):
  Global unicast address(es):
    2001:1:0:146:C005:12FF:FE30:0, subnet is 2001:1:0:146::/64 [EUI]
  Joined group address(es):
    FF02::1
    FF02::1:FF30:0
  MTU is 1500 bytes
  ICMP error messages limited to one every 100 milliseconds
  ICMP redirects are enabled
  ICMP unreachables are sent
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
Rack1R6#