It enables gradual application upgrades, one by one, to IPv6.
Cisco IOS Software Releases 12.2(2)T and later are IPv6-ready. As soon as you con?¬?gure
basic IPv4 and IPv6 on the interface, the interface is dual-stacked and forwards IPv4 and
IPv6 traf?¬?c on that interface. Figure 7-15 shows an example of this con?¬?guration.
Figure 7-15 Dual-Stack Con?¬?guration
Using IPv6 on a Cisco IOS router requires the global con?¬?guration command ipv6 unicastrouting.
This command enables the forwarding of IPv6 datagrams.
Tunneling is an integration method in which an IPv6 packet is encapsulated within another
protocol, such as IPv4. Figure 7-16 shows how IPv6 tunneling operates.
NOTE You must con?¬?gure all interfaces that forward IPv6 traf?¬?c with an IPv6 address
using the interface command ipv6 address IPv6-address [/pre?¬?x length].
Dual-Stack
Router1
conf t
ipv6 unicast-routing
interface ethernet0
ip address 192.168.99.1 255.255.255.0
ipv6 address 3ffe:b00:c18:1::3/127
IPv6 and IPv4
Network A
286 Chapter 7: Managing Address Spaces with NAT and IPv6
Figure 7-16 IPv6 Tunneling
When IPv4 is used to encapsulate the IPv6 packet, a protocol type of 41 is speci?¬?ed in the
IPv4 header, and the packet has the following characteristics:
?– Includes a 20-byte IPv4 header with no options and an IPv6 header and payload.
Pages:
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433