Static Configuration – Router
Most of the configuration commands in the Cisco routers are similar for both IPv4 as well as 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 “
For example, Configuration on Router fa0/0 and fa0/1 interfaces
Router(config-if)#ipv6 address 2001:DB8A:AACA:A::1/64
Router(config-if)#ipv6 address 2001:DB8A:AACA:B::1/64
Router(config) do wr
Static Configuration- Host
Similarly, we can configure IPv6 address is like IPv4 address. For example, 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.
Further, configuring static addresses on clients is best for a small network. For larger network dynamic assignment of IPv6 addresses is also a best practice. So, there are two ways in which a device can get an IPv6 global unicast address automatically Stateless Address Auto-Configuration (SLAAC) as well as Dynamic Host Configuration Protocol version 6 (DHCPv6) Using DHCPv6 or SLAAC, the local router’s link-local address will also automatically be specified as the default gateway address for the host.
Dynamic Configuration – SLAAC
The SLAAC is also 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 also from an IPv6 router without the use of a DHCPv6 server. All Cisco devices have also the capability of the SLAAC and, by default, SLAAC does not provide anything to the client outside of an IPv6 address and a default gateway. Using SLAAC, devices also 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.
Enter configuration commands, one per line. End with CNTL/Z.
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 also the final authority to get the IPv6 address. Further, the ICMPv6 RA message consists of:
- Network prefix as well as the prefix length
- Default gateway address
- DNS addresses as well as, domain name
There are also three options for RA messages which used to get an IPv6 address automatically:
2. SLAAC stateless DHCPv6 server
3. DHCPv6 (no SLAAC)
All Three option will also be discussed in the next lesson.