The document discusses several methods for transitioning from IPv4 to IPv6 networks, including dual stack operation, tunneling, and Network Address Translation - Protocol Translation (NAT-PT). Dual stack allows nodes to operate using both IPv4 and IPv6 simultaneously. Tunneling involves encapsulating IPv6 packets inside IPv4 packets to allow IPv6 traffic to transit IPv4 networks. NAT-PT performs translation between IPv6 and IPv4 packets to allow communication between separate IPv4 and IPv6 networks.

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Transitions
Mechanism
IPv6 to IPv4
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Edgardo Scrimaglia
CCIE
edgardo.scrimaglia@avanetworks.com.ar

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Objetives
• Describe transition mechanisms used by IPv6 network traffic to transit
IPv4 networks.
• Describe how IPv6-over-IPv4 encapsulation (tunneling) works.
• Describe how NAT-PT works.
• Explain how to express IPv4 addresses in IPv6 format.
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Transition IPv4-to-IPv6
Transition richness means:
• No fixed day to convert; no need to convert all at once.
• Different transition mechanisms are available:
– Smooth integration of IPv4 and IPv6
– Use of dual stack or 6-to-4 tunnels
• Different compatibility mechanisms:
– IPv4 and IPv6 nodes can communicate
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 Dual stack is an integration method where a node has “implementation and connectivity”
to both an IPv4 and IPv6 network.
Dual Stack
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Example Cisco IOS Dual Stack
• If both IPv4 and IPv6 are configured on an interface, this interface is dual-stacked.
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Tunneling
 Tunneling is an integration method where an IPv6 packet is encapsulated within another
protocol, such as IPv4. This method of encapsulation is IPv4 protocol 41 (Excluding Teredo):
This includes a 20-byte IPv4 header with no options and an IPv6 header and payload.
This is considered dual stacking.
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“Isolated” Dual-Stack Host
 Encapsulation can be done by edge routers between hosts or between a host and a router.
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Configuring an IPv6 Tunnel
• Configured tunnels require:
– Dual-stack endpoints
– IPv4 and IPv6 addresses configured at each end
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Example: Cisco IOS Tunnel Configuration
6in4 Tunnel
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Configuring static routes for 6-to-4 tunnels
A 6-to-4 tunnel establishes a transient link between IPv6
domains which are connected by an IPv4 backbone
• Create a tunnel interface
• Set tunnel mode with the tunnel mode ipv6ip 6to4
command
• Create an IPv6 specific address
• Set the source interface for the tunnel
• Configure an Ipv6 static route
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Converting IPv4 addresses to IPv6 for
6-to-4 Tunnel
• A 6-4 tunnel uses special addresses in the 2002::/16 address
space
• The first 16 bits are the hexadecimal number 2002
• The next 32 bits are the original source address in hexadecimal
form
• The IPv4 address of 172.16.12.1 is converted into AC10:0C01
• The complete address would be 2002:AC10:0c01:1::1/64
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Example: Cisco IOS Tunnel Configuration
6-to-4 between R1 y R3
R1
R2 R3
Lo0 10.1.2.1/24
Lo0 10.1.3.1/24
Lo0 10.1.1.1/24
172.16.12.1 /24
S0/0/0
S0/0/0
172.16.12.2 /24
S0/0/1
172.16.23.2 /24
172.16.23.1 /24
S0/0/1
R1
R1(config-if)# interface tunnel 0
R1(config-if)# tunnel mode 1pv6ip to 6to4
R1(config-if)# ipv6 address 2002:AC10:0C01:1::1/64
R1(config-if)# tunnel source s0/0/0
Exit
R1(config)# ipv6 route 2002::/16 tunnel 0
Verification
R1#ping 2002:AC10:1703:1::3
R1#ping 2002:AC10:1703:1::100 Host IPV6 (remote)
R3
R3(config-if)# interface tunnel 0
R3(config-if)# tunnel mode 1pv6ip to 6to4
R3(config-if)# ipv6 address 2002:AC10:1703:1::3/64
R3(config-if)# tunnel source s0/0/1
Exit
R3(config)# ipv6 route 2002::/16 tunnel 0
Verification
R3#ping 2002:AC10:0c01:1::1
R3#ping 2002:AC10:0c01:1::100 Host IPV6 (remote)
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IPV6 Net 2001:A:C:1::/64
IPV6 Host 2001:A:C:1::100
IPV6 Net 2001:A:B:1::/64
IPV6 Host 2001:A:B:1::100

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Cisco IOS Software Is IPv6-Ready: 6-to-4 Tunneling
• 6-to-4:
– Is an automatic tunnel method
– Gives a prefix to the attached IPv6 network
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 NAT-Protocol Translation (NAT-PT) is a translation mechanism that sits between
an IPv6 network and an IPv4 network.
 The job of the translator is to translate IPv6 packets into IPv4 packets and vice
versa.
Translation – NAT-PT
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Self Check
1. What are the 2 most common techniques to transition
from IPv4 to IPv6?
2. How does a dual-stack node choose which stack to use for
a particular traffic flow?
3. How is a router interface “dual-stacked”?
4. What is tunneling?
5. What is the job of the translator in a NAT-PT topology?
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Resumen
• The two most common techniques to transition from IPv4
to IPv6 are dual stack and IPv6-to-IPv4 (6-to-4) tunnels.
• Tunneling IPv6 traffic over an IPv4 network requires one
edge router to encapsulate the IPv6 packet inside an IPv4
packet and another router to de-encapsulate it.
• Transition methods from IPv4 to IPv6 include dual-stack
operation, protocol translation, and 6-to-4 tunnels.
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Q & A!!
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Resources
• Tunneling IPv6 through an IPv4 Network (Configuration Example)
– http://cisco.com/en/US/partner/tech/tk872/technologies_configuration_example09
186a00800b49a5.shtml
• Implementing Tunneling for IPv6
– http://cisco.com/en/US/partner/products/sw/iosswrel/ps5187/products_configurati
on_guide_chapter09186a00801d6604.html
• Cisco IOS IPv6 Configuration Library
– http://cisco.com/en/US/partner/products/sw/iosswrel/ps5187/products_configurati
on_guide_book09186a00801d65f9.html
• Network Address Translator-Protocol Translator Technical Notes
– http://www.cisco.com/en/US/products/ps6553/products_data_sheet09186a008011
ff51.html
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