IPv6 ADDRESS CONFIGURATION (EUI-64)
- EUI stands for Extended Unique Identifier
- (Modified) EUI-64 is a method of converting a MAC address (48-bits) into a 64-bit INTERFACE identifier
- This INTERFACE identifier can then become the “HOST portion” of a /64 IPv6 ADDRESS
EUI-64 PRACTICE:
782B CBAC 0867 >>> 782B CB || AC 0867
782B CBFF FEAC 0867
8 is the 7th bit so 1000 inverted becomes 1010 = A in hex
so the EUI-64 Interface Identifier is : 7A2B CBFF FEAC 0867
CONFIGURING IPv6 ADDRESSES with EUI-64
NOTE the “2001:DB8…” Address has “E” changed to “c”. This is the 7th bit getting flipped (1110 to 1100 = 12 = hex ‘C’)
WHY INVERT THE 7th BIT ?
- MAC addresses can be divided into TWO TYPES:
- UAA (Universally Administered Address)
- Uniquely assigned to the device of the manufacturer
- LAA (Locally Administered Address)
- Manually assigned by an Admin (with the mac-address command on the INTERFACE) or protocol. Doesn’t have to be globally unique.
- UAA (Universally Administered Address)
- You can INDENTIFY a UAA or LAA by the 7th bit of the MAC ADDRESS, called the U/L bit (Universal/Local bit)
- U/L bit set to 0 = UAA
- U/L bit set to 1 = LAA
- In the context of IPv6 addresses/EUI-64, the meaning of the U/L bit is reversed:
- U/L bit set to 0 = The MAC address the EUI-64 INTERFACE ID was made from was an LAA
- U/L bit set to 1 = The MAC address the EUI-64 INTERFACE ID was made from was a UAA
IPv6 ADDRESS TYPES
- GLOBAL UNICAST ADDRESSES
- Global Unicast IPv6 ADDRESSES are PUBLIC ADDRESSES which can be used over the INTERNET
- Must REGISTER to use them.
- They are PUBLIC ADDRESSES so need to be GLOBALLY UNIQUE
💡 Originally defined as the 2000 :: /3 block (2000:: to 3FFF : FFFF : FFFF : FFFF : FFFF : FFFF : FFFF : FFFF)
- NOW defined as ALL ADDRESSES which are not RESERVED for other purposes
Remember THESE THREE PARTS of a GLOBAL UNICAST ADDRESS
- UNIQUE LOCAL ADDRESSES
- Unique Local IPv6 ADDRESSES are PRIVATE ADDRESSES which cannot be used over the internet
- You do NOT need to REGISTER to use them
- Can be used FREELY within INTERNAL NETWORKS
- Do NOT need to be GLOBALLY UNIQUE (*)
- CANNOT be ROUTED over the INTERNET
- A later UPDATE required the 8th bit to be set to 1 so the FIRST TWO DIGITS must be FD
(*) The GLOBAL ID should be UNIQUE so that ADDRESSES don’t overlap when companies MERGE
- LINK-LOCAL ADDRESSES
- Link-Local IPv6 ADDRESSES are AUTOMATICALLY generated on IPv6-enabled INTERFACES
- Use command
R1(config-if)# ipv6 enableon an interface to enable IPv6 on an INTERFACE
-
The STANDARD states that the 54-bits AFTER FE80/10 should be ALL 0’s so you won’t see Link-Local ADDRESSES beginning with FE9, FEA, or FEB - ONLY FE8(!)
-
The INTERFACE ID is generated using EUI-64 rules
-
Link-Local means that these addresses are used for communication within a single link (SUBNET)
- ROUTER will not route PACKETS with a Link-Local DESTINATION IPv6 ADDRESS
-
Common uses of Link-Local Addresses:
- Routing Protocol Peerings (OSPFv3 uses Link-Local Addresses for Neighbour Adjacencies)
- NEXT-HOP ADDRESS for STATIC ROUTES
- Neighbor Discovery Protocol (NDP, IPv6’s replacement for ARP) uses Link-Local ADDRESSES to function
Network using Link-Local Addresses for “next-hop” routing
- MULTICAST ADDRESSES
- Unicast Addresses are one-to-one
- ONE SOURCE to ONE DESTINATION
- Broadcast Addresses are one-to-all
- ONE SOURCE to ALL DESTINATIONS (within the subnet)
- Multicast Addresses are one-to-many
- ONE SOURCE to MULTIPLE DESTINATIONS (that have joined the specific multicast group)
- IPv6 doesn’t use Broadcast (there IS NO “Broadcast Address” in IPv6!)
YOU MUST KNOW THE MULTICAST ADDRESS FOR EACH ROUTER TYPE
NOTE that the IPv6 and IPv4 Addresses share the same last digit
MULTICAST ADDRESS SCOPES
- IPv6 defines multiple MULTICAST ‘scopes’ which indicate how far the PACKET should be forwarded
- The ADDRESS in the previous slide all use the ‘link-local’ scope (FF02), which stays in the LOCAL SUBNET
IPv6 Multicast Scope Types:
-
Interface-Local (FF01)
- The PACKET doesn’t leave the LOCAL device
- Can be used to SEND traffic to a SERVICE within the LOCAL device
-
Link-Local (FF02)
- The PACKET remains in the LOCAL SUBNET
- ROUTERS will not route the PACKET between SUBNETS
-
Site-Local (FF05)
- The PACKET can be forwarded by ROUTERS
- Should be limited to a SINGLE PHYSICAL LOCATION (not forwarded over a WAN)
-
Organization-Local (FF08)
- Wider in scope than Site-Local (an entire company / ORGANIZATION)
-
Global (FF0E)
- No boundaries
- Possible to be ROUTED over the INTERNET
- ANYCAST ADDRESS
- ANYCAST is a NEW feature of IPv6
- ANYCAST is ‘one-to-one-of-many’
- Multiple ROUTERS are configured with the SAME IPv6 ADDRESS
- They use a ROUTING PROTOCOL to advertise the address
- When HOSTS sends PACKETS to that DESTINATION ADDRESS, ROUTERS will forward it to the NEAREST ROUTER configured with THAT IP ADDRESS (based on ROUTING METRIC)
- There is NO SPECIFIC ADDRESS range for ANYCAST ADDRESSES.
- Use a regular UNICAST (Global Unicast, Unique Local) and specify THAT as an ANYCAST ADDRESS
R1(config-if)# ipv6 address 2000:db8:1:1::99/128 anycast
- OTHER IPv6 ADDRESSES
- The :: Address = The unspecified IPv6 ADDRESS
- Can be used when a DEVICE doesn’t yet know its IPv6 ADDRESS
- IPv6 DEFAULT ROUTES are configured to ::/0
- IPv4 equivalent: 0.0.0.0
- The ::1 Address = The Loopback Address
- Used to test the PROTOCOL STACK on the LOCAL DEVICE
- Messages sent to THIS ADDRESS are processed within the LOCAL DEVICE but not SENT to other DEVICES
- IPv4 equivalent : 127.0.0.0 /8 address range