IPv6

Address Space

  • IPv6: The address space is a 128 bits as opposed to IPv4 32 bit address space
  • IPv6: The concept of address classes such as A, B, C, D doesn’t exist
  • IPV6: RFC – 4
  • 193 Unique Local Unicast FC00::/7 is equivalent to that of IPv4 RFC – 1918

Address Format

It’s crazy to think about 64 bits being allocated as the interface identifier, but this is the world of IPv6.

  • 2001:0db8:3c4d:0012:1000:2000:1a2f:1a2b
  • Site Prefix = 2001:0db8:3c4d
  • Subnet = 0012
  • Interface Identifier = 1000:2000:1a2f:1a2b

Multicast

  • With IPv6 Layer 3 broadcasts have been completely replaced with Multicast

Neighbor Discovery Protocol

  • With IPv6 ARP has been completely replaced with Neighbor Discovery Protocol or NDP

Special Reserved Addresses

  • The Loopback Address: ::1 
  • All Globally route-able addresses begin with: 2000::/3
  • Link Local Address: FE80::/10
  • All Nodes Multicast: FF02::1
  • All Routers Multicast: FF02::2
  • The Site Local Address: FEC0::/10
  • Unique Local Address: FC00::/7 – Same concept as IPv4 RFC 1918
  • Multicast Address FF00::/8
  • DHCPv6 Router solicitation destination address: FF02::/16
  • GRE Tunnel mode for IPv6 is protocol 41 as opposed to IPv4 protocol 47
  • Unlike IPv4 a single interface can have multiple IPv6 addresses with a sub-interface.

Three Rules to remember

  • Rule # 1: The HEX values in any address are not case sensitive. 
  • Rule # 2: Leading 0’s are optional. For example :0db8: can be written as :db8:
  • Rule # 3: Contiguous :0000: can be represented as :: but ONLY once.

The IEEE EUI-64 Format

The following is a typical 48 bit MAC address nothing special about it, but with IPv6 we can use the 48 bit hardware burned in MAC address as part of the IPv6 address which by all accounts should guarantee us a completely unique IPv6 address.

  • MAC: CC00.060C.0010

The IEEE’s EUI-64 standard utilizes a reserved value of 0xFFFE which by design is not available to manufacturers in the OUI portion of the MAC address. The OUI portion of the address is always the first 24 bits of the MAC address. This special reserved HEX value guarantees an even greater level of uniqueness throughout the address.   

Before we begin lets take a look at the Layer 2 burned in (bia) MAC address on Fastethernet0/0

R1#show interfaces f0/0 | include bia
 Hardware is AmdFE, address is cc00.060c.0010 (bia cc00.060c.0010)
R1#

Now lets configure the EUI-64 on inferface FastEthernet0/0.

R1#configure terminal
R1(config)#interface f0/0
R1(config-if)#ip address 2001:4:4:4::/64 eui-64
R1(config-if)#end
R1#

Now lets take a look at Fastethernet0/0 after completing the EUI-64 interface configuration.

R1#show ipv6 interface f0/0
FastEthernet1/0 is up, line protocol is up
 IPv6 is enabled, link-local address is FE80::CE00:6FF:FE0C:10
 Global unicast address(es):
 2001:4:4:4::2, subnet is 2001:4:4:4::/64
 2001:4:4:4:CE00:6FF:FE0C:10, subnet is 2001:4:4:4::/64
 Joined group address(es):
 FF02::1
 FF02::1:FF00:2
 FF02::1:FF0C:10
 MTU is 1500 bytes
 ICMP error messages limited to one every 100 milliseconds
 ICMP redirects are enabled
 ND DAD is enabled, number of DAD attempts: 1
 ND reachable time is 30000 milliseconds

Enabling IPv6 Unicast Routing

Unlike IPv4 on Cisco Routers IPv6 requires a little more work. Before or after enabling the Routing Protocol of choice you need to enable IPv6 unicast routing. The following would be equivalent to that of an IPv4 /30 address.

R1#configure terminal
R1(config)#interface Serial0/0
R1(config-if)#no ip address
R1(config-if)#ipv6 address 2001:1:1:1::1/126 
R1(config-if)#end
R1#

Now lets take a look at the available Multicast Groups before enabling IPv4 Unicst Routing.

R1#show ipv6 interface s0/0
Serial0/0 is up, line protocol is up
 IPv6 is enabled, link-local address is FE80::CE01:13FF:FE24:10
 Global unicast address(es):
 2001:1:1:1::1, subnet is 2001:1:1:1::/64
 Joined group address(es):
 FF02::1
 FF02::1:FF00:1
 FF02::1:FF24:10
 MTU is 1500 bytes
 ICMP error messages limited to one every 100 milliseconds
 ICMP redirects are enabled
 ND DAD is enabled, number of DAD attempts: 1
 ND reachable time is 30000 milliseconds

As mentioned above, now lets enable IPv6 unicast routing, and check the Multicast Groups again.

R1#configure terminal
R1(config)#ipv6 unicast-routing
R1(config)#end
R1#

We can see from the output below that there is another another Multicast FF02::2 for Unicast Routing.

R1#show ipv6 interface s0/0
Serial0/0 is up, line protocol is up
 IPv6 is enabled, link-local address is FE80::CE01:13FF:FE24:10
 Global unicast address(es):
 2001:1:1:1::1, subnet is 2001:1:1:1::/64
 Joined group address(es):
 FF02::1
 FF02::2 - - - - - - - The ALL Routers Multicast address
 FF02::1:FF00:1
 FF02::1:FF24:10
 MTU is 1500 bytes
 ICMP error messages limited to one every 100 milliseconds
 ICMP redirects are enabled
 ND DAD is enabled, number of DAD attempts: 1
 ND reachable time is 30000 milliseconds
 Hosts use stateless autoconfig for addresses

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