From: David Timmons (masterdt@yahoo.com)
Date: Wed Sep 20 2006 - 17:01:13 ART
Hi,
I was trying to figure out how Automatic IPV6 6to4 tunnels works. At the moment, I am most interested in how they are able to discover the remote side. Cisco's website has said that it uses the IPV4 address to find the other side. They have also said that no configuration is required to discover the other side. I have also read that you must have static and or BGP/routing. Since most of the examples I have seen do not have the IPV4 part of the IP on the adjacent router, I don't see how it could be used with respect to the IPV4 routing table. I have seen mentions of 6to4 IPV6 anycast. Really, I just don't understand how this technology is working. Can anyone provide some information or good sources?
looked at links like:
http://www.cisco.com/en/US/partner/tech/tk872/technologies_design_guide09186a00800d6a19.shtml
This PP seems to show up in many of Cisco's documents:
6to4 tunneling is a technique where the tunnel endpoint is determined by the globally unique IPv4 address embedded in a 6to4 address. A 6to4 IPv6 address is a combination of the unique routing prefix 2002::/16 and a globally unique 32-bit IPv4 address. (IPv4-compatible IPv6 addresses are a different format from 6to4 IPv6 addresses. IPv4-compatible IPv6 addresses are not used in 6to4 tunneling.) 6to4 tunnels are configured between border routers, or between a border router and a host. 6to4 tunnels require that a 6bone 6to4 relay site be identified to provide the 6to4 relay service to the enterprise. The 6to4 relay site will configure a dual-stack border router that will become the endpoint for the enterprise 6to4 tunnel. After the 6to4 relay site sets up for 6to4 tunneling, its management burden is minimal. At the enterprise end, a simple router configuration enables access to the 6bone through the 6to4 tunnel.
These are my current notes:
d. Automatic 6to4
i. http://www.ietf.org/rfc/rfc3964.txt
ii. Not point-to-point
iii. Point to multipoint
iv. IPV4 address is embedded in IPV6 Address
1) Used to find other end
2) IPV4 address does not need to be on same subnet
v. Normally used to connect multiple sites
1) Network is treated as a NBMA
vi. Virtual no broadcast multi-access (NBMA) link
vii. uses 6to4 IPV4 anycast RFC 3068
viii. Limitations
B7 This solution is limited to static or BGP4+ routing
ix. Example
interface Tunnel0
description IPv6 uplink
no ip address
ipv6 address 2002:c0a8:6301::1/64
tunnel source Ethernet 0
tunnel mode ipv6ip 6to4
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