IPv6 Addressing on Routers

Static unicast address configuration

There are 2 ways to configure the static address on routers,

1. Configure the full 128-bit address using the ipv6 address interface subcommand.                        eg., ipv6 address 2001:DB6:1111:2::1/64                                                                                         
2. Only configure the 64-bit prefix and let the router derive the second half of the address (Interface ID) using modified EUI-64.

How to generate a unique interface ID using Modified EUI-64?

EUI - Extended Unique Identifier

64 Bits	24 Bits	16 Bits	24 Bits
Subnet Prefix	Ist Half of MAC	FFFE	2nd Half of MAC
	Invert the 7th Bit

Example:

Step 1: MAC address of the Interface - 1523.6131.7568

Step 2: Divide the MAC into two half parts

             152361                             317568

Step 3: Insert FFFE in the middle

             152361        FFFE            317568

Step 4: Write in the IPv6 format

            1523:61FF: FE31:7568

Step 5: Invert the 7th bit (Left to Right)

             1) Write the First 2 Hex digits  -  15

             2) Convert to binary                0001 0101

             3) Invert the 7th bit                  0001 0111

             4) Convert to Hex. digit                17

Step 6:  Write the Interface ID calculated by the router using EUI-64

              1723:61FF:FE31:7568

Which command is used to configure static IPv6 address using EUI-64?

The below Interface subcommand is used 

ipv6 address 2001:de8:1112:3::/64 eui-64 

How to enable IPv6 routing on routers?

On Cisco routers, IPv4 routing is enabled by default, but not IPv6 routing.

ipv6 unicast-routing  - Global command enable IPv6 routing in routers.

How to verify the IPv6 address configuration?

• Show ipv6 interface brief

          Provides interface ipv6 address information, but not prefix length information.

• Show ipv6 interface

          Provides all the details of IPv6 interface settings.

• Show ipv6 route connected

          Display connected IPv6 routes on the router.

Dynamic Unicast Addressing on Routers

Cisco routers support 2 ways for their interface to dynamically learn an IPv6 address.

1. Stateful DHCP                                                                                                                    Command - ipv6 address dhcp interface subcommand.
2. SLAAC                                                                                                                                            Command - ipv6 address autoconfig interface subcommand.