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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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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 6to4command
• 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 Configuration6-to-4 between R1 y R3
R1
R2 R3
Lo0 10.1.2.1/24Lo0 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
R1R1(config-if)# interface tunnel 0R1(config-if)# tunnel mode 1pv6ip to 6to4R1(config-if)# ipv6 address 2002:AC10:0C01:1::1/64R1(config-if)# tunnel source s0/0/0ExitR1(config)# ipv6 route 2002::/16 tunnel 0
VerificationR1#ping 2002:AC10:1703:1::3R1#ping 2002:AC10:1703:1::100 Host IPV6 (remote)
R3R3(config-if)# interface tunnel 0R3(config-if)# tunnel mode 1pv6ip to 6to4R3(config-if)# ipv6 address 2002:AC10:1703:1::3/64R3(config-if)# tunnel source s0/0/1ExitR3(config)# ipv6 route 2002::/16 tunnel 0
VerificationR3#ping 2002:AC10:0c01:1::1R3#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
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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Resources
• Tunneling IPv6 through an IPv4 Network (Configuration Example)
– http://cisco.com/en/US/partner/tech/tk872/technologies_configuration_example09186a00800b49a5.shtml
• Implementing Tunneling for IPv6
– http://cisco.com/en/US/partner/products/sw/iosswrel/ps5187/products_configuration_guide_chapter09186a00801d6604.html
• Cisco IOS IPv6 Configuration Library
– http://cisco.com/en/US/partner/products/sw/iosswrel/ps5187/products_configuration_guide_book09186a00801d65f9.html
• Network Address Translator-Protocol Translator Technical Notes
– http://www.cisco.com/en/US/products/ps6553/products_data_sheet09186a008011ff51.html
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