1. 1 IPv4 (Part III) รศ. ดร. อนันต์ ผลเพิ่ม Asso. Prof. Anan Phonphoem, Ph.D. anan.p@ku.ac.th http://www.cpe.ku.ac.th/~anan Computer Engineering Department Kasetsart University, Bangkok, Thailand Dec 2011

2. 2 Outline IP Fundamental Operation Internet Protocol Addressing Supporting Protocol ARP ICMP: ping + traceroute NAT DHCP

3. 3 Network Address Translation (NAT)

4. 4 Private Network Good practice to use private address Map local addresses to (real) public IP address(es) Security (not expose internal details) Alleviate IP depletion

5. 5 Private IP address ClassRFC 1918CIDR prefix A10.0.0.0 – 10.255.255.25510.0.0.0/8 B172.16.0.0 – 172.16.255.255172.16.0.0/12 C192.168.0.0 – 192.168.255.255192.168.0.0/16

6. 6 NAT Operates at the border of a stub network

7. 7 NAT

8. 8 ADSL Router WLAN ADSL Router ADSL Connection ADSL Modem Internet ISP Telephone Line ADSL Modem ADSL Modem

9. 9 Configure NAT Static Translation Dynamic Translation

10. 10 Static Translation

11. Example 11

12. 12 Dynamic Translation

13. 13 PAT: Port Address Translation (Overloaded NAT)

14. 14 PAT 179.9.8.80

15. 15 Disadvantages of NAT Delay Loss of end-to-end ability Might not work with some applications

16. 16 Bootstrap Protocol (BOOTP)

17. 17 BOOTP Diskless terminal Discover its own IP address Download executable image file Small program built in chip BOOTH and TFTP Application Protocol Encapsulated in IP and UDP

18. 18 BOOTP packet format

19. 19 Operation

20. 20 Dynamic Host Configuration Protocol (DHCP)

21. 21 DHCP BOOTP Enhancement Same message structure as BOOTP Can choose among many DHCP servers

22. 22 DHCP packet

23. 23 Operation

24. 24 DHCP Message

25. 25 DHCP transition diagram

26. 26 DHCP Relay

27. 27 DHCP Relay

28. 28 Summary IP Fundamental Operation Internet Protocol Addressing Supporting Protocol ARP ICMP: ping + traceroute NAT DHCP