> # Dual IPv4 and IPv6 Protocol Stacks

> The dual IPv4 and IPv6 protocol stack technique is one technique for a transition to IPv6. It enables gradual, one-by-one upgrades to applications running on nodes. Applications running on nodes are upgraded to make use of the IPv6 protocol stack. Applications that are not upgraded—they support only the IPv4 protocol stack—can coexist with upgraded applications on the same node. New and upgraded applications simply make use of both the IPv4 and IPv6 protocol stacks.

> A new API has been defined to support both IPv4 and IPv6 addresses and DNS requests. An application can be upgraded to the new API and still use only the IPv4 protocol stack. The Cisco MDS NX-OS supports the dual IPv4 and IPv6 protocol stack technique. When an interface is configured with both an IPv4 and an IPv6 address, the interface will accept and process both IPv4 and IPv6 traffic.

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