Unsupported IPv6 Unicast Routing Features

Chapter 39 Configuring IPv6 Unicast Routing

Understanding IPv6

•DNS resolver for AAAA over IPv4 transport

•Cisco Discovery Protocol (CDP) support for IPv6 addresses

For more information about managing these applications with Cisco IOS, see the “Managing Cisco IOS Applications over IPv6” chapter in the Cisco IOS IPv6 Configuration Library at this URL:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5187/products_configuration_guide_chapter0918 6a00801d65f3.html

Dual IPv4 and IPv6 Protocol Stacks

One technique for transitioning to IPv6 is by using dual IPv4 and IPv6 protocol stacks. Using dual stacks enables gradual, one-by-one upgrades to applications running on nodes. Applications that are upgraded to IPv6 use the IPv6 protocol stack, and applications that are not upgraded and support only IPv4 can coexist with upgraded applications on the same node. New and upgraded applications can use both IPv4 and IPv6 protocol stacks.

The Cisco IOS software supports the dual IPv4 and IPv6 protocol stack technique. When both IPv4 and IPv6 routing are enabled and an interface is configured with both an IPv4 and IPv6 address, the interface forwards both IPv4 and IPv6 traffic.

Figure 39-1shows a router forwarding both IPv4 and IPv6 traffic through the same interface, based on the IP packet and destination addresses.

Figure 39-1 Dual IPv4 and IPv6 Support on an Interface

IPv4

IPv6

10.1.1.1

122379

3ffe:yyyy::1

The switch uses hardware memory to store unicast routes, MAC addresses, access control lists (ACLs), and other features, and provides the switch database management (SDM) templates to allocate memory resources depending on how the switch is used. You must use the dual IPv4 and IPv6 template templates to allocate hardware memory usage to both IPv4and IPv6 protocols. See the “SDM Templates” section on page 39-9.