Reply message exchange with the IPv6-only host using steps 1 through 7 of the “Initial Communication from a Teredo Client to an IPv6-Only Host” (for a restricted NAT) section of this chapter. After this exchange is complete, the Teredo client sends the response to the initial communication packet to the IPv6-only host.

References

The following references were cited in this chapter:

■RFC 1631 — “The IP Network Address Translator (NAT)”

■RFC 4380 — “Teredo: Tunneling IPv6 over UDP through Network Address Translations (NATs)”

You can obtain these RFCs from the \RFCs_and_Drafts folder on the companion CD-ROM or from http://www.ietf.org/rfc.html.

Testing for Understanding

To test your understanding of Teredo, answer the following questions. See Appendix D, “Testing for Understanding Answers,” to check your answers.

1.Describe the intended use of the Teredo IPv6 transition technology.

2.How can you recognize a Teredo address?

3.How are the source and destination addresses in the encapsulating IPv4 header determined for Teredo-tunneled traffic to another Teredo client?

4.Why are portions of the Teredo address obscured?

5.What is the difference between a Teredo relay and a Teredo host-specific relay?

6.A Teredo client has the address 2001::62C3:1B8D:346B:EBC9:7C94:EA26. Is this client behind a cone NAT or a restricted NAT? What is the public IPv4 address of its Teredo server? What are the external IPv4 address and UDP port number for this Teredo client’s Teredo traffic?

7.How does a Teredo client determine the external IPv4 address and UDP port number for its traffic during the Teredo address configuration process?

8.Initial communication between two Teredo clients in different sites when both Teredo clients are behind restricted NATs requires four more packets than when both Teredo clients are behind cone NATs. What is the purpose of these four additional packets?

9.How does a Teredo client determine the public IPv4 address of the Teredo relay when initiating communication to a host on the IPv6 Internet?