IPv6 Configuration (Cont.)

Tunnel Configuration

Configuration for tunneling an IPv6 Routing Information Protocol (RIP), and an IPv6 Border Gateway Protocol (BGP) network and traffic through a pre-existing IPv4 network. This technique allows you to connect IPv6 sites over the IPv4 backbone that exists.

Overlay tunneling encapsulates IPv6 packets in IPv4 packets for delivery across an IPv4 infrastructure. This is similar to how you create a generic routing encapsulation (GRE) tunnel to transport Internetwork Packet Exchange (IPX) traffic through an IP network. At the tunnel head end, an IPv6 packet is encapsulated into IPv4 packet and sent to the remote tunnel destination. This is where the IPv4 packet header is stripped, and the original IPv6 packet is forwarded further into an IPv6 cloud.

These are the five methods of tunneling IPv6 traffic:

• Manual IPv6 tunnels
• Automatic IPv4-Compatible tunnels
• GRE
• Automatic 6to4 tunnels
• Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) Tunnels

The primary difference in these tunneling techniques is the method in which the tunnel source and destination are determined. In this document, the manual and Automatic IPv4 Compatible tunnel types are described. Refer to Implementing Tunneling for IPv6for information on other tunneling techniques and their characteristics.

Overlay tunnels reduce the maximum transmission unit (MTU) of an interface by 20 octets. This assumes that the basic IPv4 packet header does not contain optional fields. A network that uses overlay tunnels is difficult to troubleshoot. Therefore, overlay tunnels that connect isolated IPv6 networks should not be considered as a final IPv6 network architecture. The use of overlay tunnels should be considered as a transition technique toward a network that supports both the IPv4 and IPv6 protocol stacks, or just the IPv6 protocol stack.

Prerequisites

Requirements

Cisco recommends that you have knowledge of IPv6 before you attempt this configuration. Refer to Implementing IPv6 Addressing and Basic Connectivity for information on IPv6.

Components Used

The information in this document is based on Cisco 36xx series routers that run Cisco IOS^® Software Release 12.3(13).

Any hardware platform which supports Cisco IOS Software Release 12.2(2)T or 12.0(21)ST and later also supports IPv6.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool (registered customers only) to find more information on the commands used in this document.

Network Diagram

This document uses this network setup:

Configurations (Manual IPv6 Mode)

The configuration of manually configured tunnels for IPv6 is self-explanatory. It requires definite specification of the tunnel IPv4 source and the tunnel IPv4 destination. The only drawback of when you use this technique is the amount of administration you must perform when the number of tunnels grows.

This document uses these configurations for the manual IPv6 mode:

• R1-IPv6
• R2-IPv6-IPv4
• R3-IPv4
• R4-IPv4-IPv6
• R5-IPv6

R1-IPv6 (Cisco 3640 Router)

R1-ipv6#show run Building configuration... Current configuration : 916 bytes ! version 12.3 hostname R1-ipv6 ! boot system flash logging buffered 4096 debugging ! ip subnet-zero ip cef ! ! no ip domain-lookup ! ipv6 unicast-routing ! ! ! ! interface Ethernet0/0 no ip address shutdown ! interface Ethernet0/1 no ip address ipv6 address 2000:1:1:1:1:1:1:1112/112 ipv6 rip 6bone enable ! ! ip classless ! ipv6 router rip 6bone ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! ! ! end

R2-IPv6-IPv4 (Cisco 3640 Router)

R2-ipv6-ipv4#show run Building configuration... Current configuration : 1079 bytes ! version 12.3 ! hostname R2-ipv6-ipv4 ! ip subnet-zero ! ! ipv6 unicast-routing ! ! interface Tunnel0 no ip address ipv6 address 3000::1/112 ipv6 rip 6bone enable tunnel source Serial0/0 tunnel destination 192.34.1.4 tunnel mode ipv6ip !--- Configures Manual tunnel. !--- In some cases, user would require a Data License !--- in order to issue "tunnel mode ipv6ip" ! ! interface Serial0/0 ip address 192.23.1.2 255.255.255.0 clockrate 64000 ! interface FastEthernet0/1 no ip address duplex auto speed auto ipv6 address 2000:1:1:1:1:1:1:1111/112 ipv6 rip 6bone enable ! router ospf 1 log-adjacency-changes network 192.23.1.0 0.0.0.255 area 0 ! ip classless ! ipv6 router rip 6bone ! ! line con 0 line aux 0 line vty 0 4 login line vty 5 15 login ! ! end

R3-IPv4 (Cisco 2621 Router)

R3-ipv4#show run Building configuration... Current configuration : 865 bytes ! version 12.3 ! hostname R3-ipv4 ! ! memory-size iomem 15 ip subnet-zero ! ! interface Serial0/0 ip address 192.23.1.3 255.255.255.0 ! interface Serial0/1 ip address 192.34.1.3 255.255.255.0 ! router ospf 1 log-adjacency-changes network 192.23.1.0 0.0.0.255 area 0 network 192.34.1.0 0.0.0.255 area 0 ! ip classless ! line con 0 line aux 0 line vty 0 4 ! ! end

R4-IPv4-IPv6 (Cisco 3640 Router)

R4-ipv4-ipv6#show run Building configuration... Current configuration : 1413 bytes ! version 12.3 ! hostname R4-ipv4-ipv6 ! ! ip subnet-zero ! ! no ip domain-lookup ! ipv6 unicast-routing ! ! ! interface Tunnel0 no ip address ipv6 address 3000::2/112 ipv6 rip 6bone enable tunnel source Serial1/5 tunnel destination 192.23.1.2 tunnel mode ipv6ip !--- Configures Manual tunnel. ! ! interface Serial1/5 ip address 192.34.1.4 255.255.255.0 clockrate 64000 ! ! interface Ethernet3/0 no ip address half-duplex ipv6 address 4000:1:1:1:1:1:1:1111/112 ipv6 rip 6bone enable ! router ospf 1 log-adjacency-changes network 192.34.1.0 0.0.0.255 area 0 ! ip classless ! ipv6 router rip 6bone ! ! line con 0 line aux 0 line vty 0 4 login ! ! end

R5-IPv6 (Cisco 7500 Router)

R5-ipv6#show run Building configuration... Current configuration : 1001 bytes ! version 12.3 ! hostname R5-ipv6 ! ip subnet-zero ip cef distributed ! ! no ip domain-lookup ! ipv6 unicast-routing ! ! ! interface Ethernet1/2 no ip address ipv6 address 4000:1:1:1:1:1:1:1112/112 ipv6 rip 6bone enable ! ! ip classless ! ipv6 router rip 6bone ! ! ! line con 0 exec-timeout 0 0 line aux 0 line vty 0 4 login ! ! end