> # IPv6 Addressing and Enabling IPv6 Routing

> IPv6 addresses are represented as a series of 16-bit hexadecimal fields separated by colons (:) in the format x:x:x:x:x:x:x:x. It is common for IPv6 addresses to contain successive hexadecimal fields of zeros. To make IPv6 addresses easier to use, two colons (::) may be used to compress successive hexadecimal fields of zeros at the beginning, middle, or end of an IPv6 address (the colons represent successive hexadecimal fields of zeros). By default, IPv6 addresses are not configured, and IPv6 processing is disabled. You can configure IPv6 addresses on the following interface types:

> - Gigabit Ethernet
> - Management
> - VLAN (Gigabit Ethernet subinterface)
> - VSAN

> Configuring a global IPv6 address on an interface automatically configures a link-local address and activates IPv6 for that interface. Additionally, the configured interface automatically joins the following required multicast groups for that link:

> - Solicited-node multicast group FF02:0:0:0:0:1:FF00::/104 for each unicast address assigned to the interface
> - All-node link-local multicast group FF02::1

> This task explains how to assign IPv6 addresses to individual router interfaces and enable the processing of IPv6 traffic. By default, IPv6 addresses are not configured and IPv6 processing is disabled.

> You can configure IPv6 addresses on the following interface types:

> - Gigabit Ethernet
> - Management
> - VLAN (Gigabit Ethernet subinterface)
> - VSAN

> Note The IPv6 address must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
> The IPv6 prefix must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
> The IPv6 prefix length is a decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). A slash mark must precede the decimal value.

> Configuring a global IPv6 address on an interface automatically configures a link-local address and activates IPv6 for that interface. Additionally, the configured interface automatically joins the following required multicast groups for that link:

> - Solicited-node multicast group FF02:0:0:0:0:1:FF00::/104 for each unicast address assigned to the interface
> - All-node link-local multicast group FF02::1

> Note The solicited-node multicast address is used in the neighbor discovery process.

> Note The maximum number of IPv6 addresses (static and autoconfigured) allowed on an interface is eight, except on the management (mgmt 0) interface where only one static IPv6 address can be configured.

> Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.