Configuring IPv6 on a Cisco Router

With the IPv4 public address space running out very fast, we will soon be adopting IPv6. Many enterprises and ISP's are already using IPv6 in their core networks.

When the rest of the world come to adopt this new technology, you will need to know how to configure interfaces and routing protocols.

Many Cisco routers already have the IPv6 functionality built into the IOS. Some earlier releases of Cisco's IOS do not have IPv6 available. In this case, you may have to go to the Cisco website and download the latest IOS image for your router.

IPv6 Basic Addressing

There are a few types of IPv6 addressing, the main ones you will use are link local and global unicast addresses.

Link-Local addresses can only be used in the context of a layer two domain.

Global Unicast addresses are used to get into the internet. These are like IPv4 public IP addresses. They are used to access resources outside of the current network/vlan.

Lets see how we configure link-local and global addresses:

IPv6-Router(config)# ipv6 unicast-routing

This command enables routing for IPv6. Much like the command 'ip routing'

Now lets configure some addresses:

IPv6-Router(config)# interface GigabitEthernet0/0
IPv6-Router(config-if)# ipv6 address 2001:db8::1/64
IPv6-Router(config-if)# ipv6 address fe80::1 link-local

Here we configured the interface with a global unicast and link local address

It is best practice to hard code the link local address to something you can remember and that corresponds to an interface or vlan. This makes troubleshooting easier. A non hard-coded link local address will most likely be configured by EUI-64. You can read more about that here.