IPv6 addresses are 128 bits long and are represented in hexadecimal notation, separated by colons. They are divided into eight 16-bit blocks, each of which is represented by four hexadecimal digits. Leading zeros in each block can be omitted, and consecutive blocks of zeros can be replaced with a double colon (::), but only once in an address.
To configure IPv6 addressing on a Cisco router or switch, you can use the following steps:
Enter global configuration mode:
Router> enable
Router# configure terminal
Assign a unique IPv6 address to the interface:
Router(config)# interface interface_name
Router(config-if)# ipv6 address ipv6_address/prefix_length
For example, to assign the address 2001:db8::1/64 to interface GigabitEthernet0/0, you would enter the following commands:
Router(config)# interface GigabitEthernet0/0
Router(config-if)# ipv6 address 2001:db8::1/64
Enable the interface with the no shutdown command:
Router(config-if)# no shutdown
Router(config)# ipv6 route ::/0 next-hop ipv6_address
For example, to configure the default gateway as 2001:db8::2, you would enter the following command:
Router(config)# ipv6 route ::/0 next-hop 2001:db8::2
Verify the IPv6 address configuration using the show ipv6 interface command:
Router# show ipv6 interface
Check this video: Tutorial on IPv6