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 2012

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 Stub Network Operates at the border of a stub network

7. 7 ADSL Router WLAN ADSL Router Stub Network Example ADSL Connection ADSL Modem Internet ISP Telephone Line ADSL Modem ADSL Modem

8. 8 NAT “One” or “Pool” of IP addresses

9. Example 9 200.24.5.8172.18.3.254

10. 10 Configure NAT Static Translation Dynamic Translation

11. 11 Static Translation

12. 12 Dynamic Translation Many-to-one Mapping ??? Many inside IP  one outside IP

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 Find out what application does not work with NAT ?

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