39-6
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02
Chapter39 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. U sing dual stacks
enables gradual, one-by-one upgrades to applications runni ng 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 c an use both IPv4
and IPv6 protocol stacks.
The Cisco IOS software supports the dual IPv4 and IPv6 protocol stack techniqu e. 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 39-1 shows a router forwarding both IPv4 and IPv6 traffic through the same interface, ba sed on
the IP packet and destination addresses.
Figure39-1 Dual IPv4 and IPv6 Support on an Interface
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 alloc ate 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.
Unsupported IPv6 Unicast Routing Features
The switch does not support these IPv6 features in this release:
•IPv6 policy-based routing
•IPv6 virtual private network (VPN) routing and forwarding (VRF) table support
•Support for these IPv6 routing protocols: Multiprotocol Border Gateway Protocol (BGP),
Intermediate System-to-Intermediate System (IS-IS) routing, Enhanced Interior Gateway Routing
Protocol (EIGRP)
122379
3ffe:yyyy::1
10.1.1.1
IPv6
IPv4