Introduction; 6To4 Automatic Tunnel Configuration; Tunneling Operation - Allied Telesis SwitchBlade x908 Series Software Reference Manual

IPv6to4 Tunneling Configuration

Introduction

This chapter contains a basic IPv6to4 automatic tunneling configuration example for reference.
To see details on the Tunneling commands used in this sample configuration, or to see the
outputs of the Validation commands, refer to
to the Tunneling commands used in the examples are also provided below the examples.

6to4 Automatic Tunnel Configuration

IPv6 transition is required to migrate from IPv4 to IPv6. One method to connect to the global
IPv6 network over the existing IPv4 network is called 6to4 automatic tunneling.
Although this method is called '6to4 tunneling', it does not involve discrete point-to-point
tunnels. The 'tunneling' in '6to4 tunneling' refers to the fact that the IPv6 packets are
encapsulated in IPv4 packets to be 'tunneled' across the IPv4 domain. Hence, '6to4 tunneling' is
primarily a scheme for encapsulating IPv6 packets inside IPv4 headers.
Using 6to4 tunneling, you are not required to specify tunnel destination addresses. You only
choose the interface that connects the switch to the IPv4 domain, and designate that interface
to be the tunnel entry-point. As will be explained below, the IPv4 address that represents the
point at which any given IPv6 packet will eventually exit the IPv4 domain is derived from the
IPv6 packet itself. Note that the packet's destination IPv6 address itself contains the destination
IPv4 address that is used for tunnel encapsulation.
The 6to4 tunneling implementation in AlliedWare Plus
IPv6 addresses that are of the form:
2002: <valid-IPv4-unicast-address> : XX:XX:XX:XX:XX
6to4 tunneling makes use of the fact that for every valid IPv4 unicast address A.B.C.D, there
is always a corresponding valid IPv6 subnet 2002:<A.B.C.D>::/48. So, for every global
IP v4 address that has been allocated to an organization, there is immediately a global IPv6
subnet 2002:<ipv4-address>::/48 available to that organization.

Tunneling Operation

When an IPv4 interface on the switch is designated as a tunnel entry point, using the
source command on page 27.5
automatically allocated the IPv6 address: 2002:<ipv4-address>::1/128.
Note:
This tunnel interface is the gateway used by the IPv6 packets to enter the IPv4 domain. As IPv6
packets enter the IPv4 domain, the switch must encapsulate them by pre-pending IPv6 packets
with an IPv4 header. The source address of the encapsulating header is the IPv4 address that
has been specified by the tunnel source command. The process for determining the destination
IP address is explained in more detail below and on the following page.
The key to routing across the IPv4 domain is that there is a connection between the IPv4
address of a tunnel endpoint and the IPv6 subnets which can be reached via that endpoint.
The connection is that the tunnel interface with IP address <ipv4-address> is considered
to be the gateway to all IPv6 subnets within the range 2002:<ipv4-address>::/48.
26.2
command, an IPv6 tunnel interface is created. The interface is
Other implementations of 6to4 tunneling might have a different scheme for deriving
the IPv6 address of the tunnel interface, as there is no standardized scheme. This
does not cause any interoperability problems, however, as the IPv6 address of the
tunnel interface is not actually involved in the routing process.
Software Reference for SwitchBlade® x908, x900 and x600 Series Switches
TM
AlliedWare Plus Operating System - Software Version 5.3.1
Chapter 27, IPv6to4 Tunneling
TM
5.3.1 is used for routing only between
Commands. Links
tunnel
C613-50007-01 REV B