Configuration of Global IPv6 Unicast Address

Static Configuration – Router

Most of the configuration commands in the Cisco routers are similar for both IPv4 and IPv6. The only difference is the use of ipv6 in place of IP within the commands. The command to configure an IPv6 global unicast address on any interface is “ipv6 address ipv6-address/prefix-length “

Example Configuration on Router fa0/0 and fa0/1 interfaces


Router#configure terminal

Router(config)interface fa/0/0

Router(config-if)#ipv6 address 2001:DB8A:AACA:A::1/64

Router(config-if)no shutdown


Router(config)interface fa/0/1

Router(config-if)#ipv6 address 2001:DB8A:AACA:B::1/64

Router(config-if)no shutdown


Router(config) do wr

Building configuration…


Static Configuration- Host

Manual configuration of the IPv6 address is similar to configure an IPv4 address. As shown in Figure, the default gateway address configured for PC1 is 2001:DB8A:AACA:A::1. This is the global unicast address of the Router Fast Ethernet interface 0/0 on the same network. Link-local address of the router can also be configured as the gateway for the host. Both configurations will work.


Configuring static addresses on clients is best for a small network. For larger network dynamic assignment of IPv6 addresses is best practice.

There are two ways in which a device can get an IPv6 global unicast address automatically:

  • Stateless Address Auto Configuration (SLAAC)
  • Dynamic Host Configuration Protocol version 6 (DHCPv6)

Using DHCPv6 or SLAAC, the local router’s link-local address will automatically be specified as the default gateway address for the host.

Dynamic Configuration – SLAAC

The SLAAC is a unique feature for IPv6 addresses. Stateless address configuration means that a device to obtain its prefix, prefix length, default gateway address, and other information from an IPv6 router without the use of a DHCPv6 server. All Cisco devices have the capability of the SLAAC. By default, SLAAC does not provide anything to the client outside of an IPv6 address and a default gateway. Using SLAAC, devices rely on the local router’s ICMPv6 Router Advertisement (RA) messages to obtain the necessary information.

IPv6 enabled routers to send out ICMPv6 RA messages after every 200 seconds, to all IPv6-enabled devices on the network. An RA message will also be sent in response to a host sending an ICMPv6 Router Solicitation (RS) message.

IPv6 routing is not enabled by default. To enable a router IPv6 following command will be used.


Router#configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#ipv6 unicast-routing


The ICMPv6 RA Message

The ICMPv6 RA message is a suggestion to a device on how to get an IPv6 global unicast address. The device operating system is final authority to get the IPv6 address. The ICMPv6 RA message consists of:

  • Network prefix and prefix length
  • Default gateway address
  • DNS addresses and domain name

There are three options for RA messages which used to get an IPv6 address automatically:


2. SLAAC with a stateless DHCPv6 server

3. DHCPv6 (no SLAAC)

All Three option will be discussed in next lesson.