IPv6 Dual Stack

IPv6 was delivered with  some migration techniques,one of the technique called dual stack
it is a way to implement IPv6 and still remain compatible with IPv4 to run Both IPv4 and IPv6
either independently or in a hybrid form. The hybrid form is commonly implemented in modern operating systems supporting IPv6.Dual-stack hosts are described in RFC 4213.

Example of configure:
Two IPv6/IPv4 nodes, R1 and R2, are connected to each other via a GigabitEthernet interface.
The GigabitEthernet interface is configured with an IPv4 as well as an IPv6 address



R1:

ipv6 unicast-routing
ipv6 cef
!
interface Loopback 0
 ip address 1.1.1.1 255.255.255.255
!
interface Loopback 1
 ipv6 address 2002:ABAA::/64 eui-64
 ipv6 rip YANIV enable
!
interface GigabitEthernet1/0
 ip address 11.1.1.1 255.255.255.252
 ipv6 address 2001::/64 eui-64
 ipv6 rip YANIV enable
!
router ospf 1
 network 1.1.1.1 0.0.0.0 area 0
 network 11.1.1.0 0.0.0.3 area 0
!
ipv6 router rip YANIV

________________________________

R2:

ipv6 unicast-routing
ipv6 cef
!
interface Loopback 0
 ip address 2.2.2.2 255.255.255.255
!
interface Loopback 1
 ipv6 address 2003:ABAA::/64 eui-64
 ipv6 rip YANIV enable
!
interface GigabitEthernet1/0
 ip address 11.1.1.2 255.255.255.252
 ipv6 address 2001::/64 eui-64
 ipv6 rip YANIV enable
!
router ospf 1
 network 2.2.2.2 0.0.0.0 area 0
 network 11.1.1.0 0.0.0.3 area 0
!
ipv6 router rip YANIV
!

___________________________________________

R1#sh ip interface brief
Interface              IP-Address      OK? Method Status                Protocol
FastEthernet0/0        unassigned      YES unset  administratively down down   
GigabitEthernet1/0     11.1.1.1        YES manual up                    up     
Loopback0              1.1.1.1         YES manual up                    up     
Loopback1              unassigned      YES unset  up                    up

R1#show ip route | begin Gateway
Gateway of last resort is not set

     1.0.0.0/32 is subnetted, 1 subnets
C       1.1.1.1 is directly connected, Loopback0
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/2] via 11.1.1.2, 00:01:22, GigabitEthernet1/0
     11.0.0.0/30 is subnetted, 1 subnets
C       11.1.1.0 is directly connected, GigabitEthernet1/0

R1#sh ipv6 interface brief
FastEthernet0/0            [administratively down/down]
    unassigned
GigabitEthernet1/0         [up/up]
    FE80::C800:8FF:FE7C:1C
    2001::C800:8FF:FE7C:1C
Loopback0                  [up/up]
    unassigned
Loopback1                  [up/up]
    FE80::C800:8FF:FE7C:0
    2002:ABAA::C800:8FF:FE7C:0

R1#show ipv6 route
IPv6 Routing Table - 7 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
C   2001::/64 [0/0]
     via ::, GigabitEthernet1/0
L   2001::C800:8FF:FE7C:1C/128 [0/0]
     via ::, GigabitEthernet1/0
C   2002:ABAA::/64 [0/0]
     via ::, Loopback1
L   2002:ABAA::C800:8FF:FE7C:0/128 [0/0]
     via ::, Loopback1
R   2003:ABAA::/64 [120/2]
     via FE80::C801:8FF:FE7C:1C, GigabitEthernet1/0
L   FE80::/10 [0/0]
     via ::, Null0
L   FF00::/8 [0/0]
     via ::, Null0

Further reading:

http://www.cisco.com/web/strategy/education/us_education/transition_to_IPv6_for_education.html

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6553/aag_c45-625513.pdf

http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/12_4t/ipv6_12_4t_book.html

http://www.cisco.com/en/US/technologies/tk648/tk872/technologies_white_paper0900aecd8026003d.pdf

http://packetlife.net/media/library/8/IPv6.pdf