1. Spring 20031 Ch 18 IP Addresses

2. 2 Internet Protocol  Only protocol at Layer 3  Defines Internet addressing Internet packet format Internet routing

3. 3 IP Addressing  Independent of hardware addressing  Used by Higher-layer protocols Applications  IP address 32-bit integer Dotted decimal notation (e.g., 140.128.11.20) Each connection must be assigned one unique IP address

4. 4 IP Address Details  Divided into two parts Prefix identifies network (net ID) Suffix identifies host (host ID)  max. number of host  Global authority assigns unique prefix to network  Local administrator assigns unique suffix to host

5. 5 IP Address Details 140.128163.23.1.2.5.8 140.128.1.1163.23.1.8  Default gateway.12.24.12.23.5.2 DNS

6. 6 Original Classes of IP Addresses

7. 7 Dotted Decimal Notation  Four decimal values per 32-bit address  Each decimal number Represents eight bits Is between 0 and 255

8. 8 Dotted Decimal Notation  Range for different classes of addresses Class A: 0.0.0.0 - 127.255.255.255 Class B:128.0.0.0 - 191.255.255.255 Class C:192.0.0.0 - 223.255.255.255 Class D:224.0.0.0 -239.255.255.255 Class E:240.0.0.0 -247.255.255.255

9. 9 Addressing Examples

10. 10 Division of the Address Space 10. x. y. z 24-bit7-bit

11. 11 Subnet and Classless Addressing 172.21.0.0 172.22.0.0 172.23.0.0 172.24.0.0 172.25.0.0  Exhaust five class-B addresses

12. 12 Subnet and Classless Addressing  Subnetting 172.21 16 bits8 bits Class B Host Id 8 bits X0 Net IdSubnet Id 172.21.1.0 172.21.5.0 172.21.4.0 172.21.3.0 172.21.2.0

13. 13 Address Mask  Accompanies IP address  32 bit binary value Net ID = 172.21 Subnet ID 16 bits8 bits Class B Host ID 8 bits Subnet mask 111…………….111……100…..0 = 255.255.255.0 or 172.21.0.0 / 24 16 bits10 bits Class B Host ID 6 bits Subnet mask 111…………….111……111 000000 = 255.255.255.192 or 172.21.0.0 / 26 Net ID = 172.21 Subnet ID

14. 14 CIDR Notation  Uses slash notation  Example 128.211.0.0/17 Means that the boundary between prefix and suffix occurs after the first 17 bits

15. 15 IP Address Allocation – Static public IP address (by hand) private IP address (via NAT, IP sharing) – Dynamic public IP address (via DHCP or relay agent)

16. 16 Special Addresses  0.0.0.0  140.128.0.0  140.128.255.255  255.255.255.255  127.0.0.1

17. 17 Special Addresses  Loopback never leaves local computer  Multi-homed hosts A host that connects to multiple networks