1. IP Addressing – Part 2 MIS 4700 – Advanced Networking Dr. Garrett

2. Vanishing IP Address Space • Mid-1990s experts began to predict that the Internet would “run out” of available IP addresses • Address space saving techniques • Classless Inter-Domain Routing (CIDR) • Trade in existing IP network addresses ($) • RFC 1918 private IP addresses range • Network Address Translation (NAT) lets networks use private IP addresses internally and maps them to public IP address externally

3. Understanding Basic Binary Arithmetic • Binary equivalents • 0000 (0), 0001 (1), 0010 (2), 0011 (3) • 0100 (4), 0101 (5), 0110 (6), 0111 (7) • 1000 (8), 1001 (9), 1010 (10), 1011 (11) • 1100 (12), 1101 (13), 1110 (14), 1111 (15) • Converting decimal to binary • Division or subtraction methods • Converting binary to decimal • Add powers of 2 for each bit placement

4. Understanding Basic Binary Arithmetic (cont.) • High-Order bit patterns • Left most bits of an octet • 11000000 • Low-Order bit patterns • Right most bits of an octet • 00000011

5. IP Networks, Subnets, And Masks • Class A, B, and C default masks • a mask is a special bit pattern that identifies the network portion of an IP address • network prefix • extended • network prefix • IP subnets and supernets • Network addresses are further subdivided beyond their defaults with subnet masks “stealing bits” from the host portion, this is called subnetting • Supernetting combines contiguous network addresses

6. IP Networks, Subnets, And Masks (cont.) • Calculating subnet masks • 2b – 2 = (the number of usable subnets) • Constant-Length Subnet Mask (CLSM) • Subnetting into multiple equal segments • Each subnet includes the same number of stations • Variable-Length Subnet Mask (VLSM) • Subnetting into multiple unequal segments • Each subnet may not have the same number of stations • Calculating supernets • Supernets “steal” bits from the network portion of an IP address to “lend” those bits to the host

7. Classless Inter-Domain Routing (CIDR) • Ignores the traditional A, B, and C class designations for IP addresses • Allows IP addresses from Class A, B, or C to be combined as a larger address space • CIDR limitations: • Network address must be contiguous • Routers in the routing domain must understand CIDR notation

8. Public Versus Private IP Addresses • Private IP addresses: • RFC 1918 designates specific addresses for use as private IP addresses • Private IP addresses are not routed across the public Internet • Public IP addresses: • Used when identifying servers or services that must be accessible to the Internet • Assigned to routers, proxy servers, firewalls, web servers, e-mail servers, FTP servers, and news servers

9. Private Address Ranges

10. Managing Access To IP Address Information • IP security • Private IP addresses and NAT • Proxy server • Reverse proxy

11. Obtaining Public IP Addresses • Public IP addresses issued by ISPs • ICANN manages all • IP-related addresses • Protocol numbers • well-known port addresses • assigns MAC layer addresses • www.icann.org

12. IP Addressing Schemes • The Network space • Number of physical locations • Number of network devices at each location • Amount of broadcast traffic at each location • IP network is a broadcast domain • Routing (instead of bridging) is done to prevent unnecessary broadcasts from clogging expensive WAN circuits 2 • Availability of IP addresses

13. IP Addressing Schemes (cont.) • The Network space (cont.) • Delay caused by routing from one network to another • Size of the routing tables • Time required for the network to “converge” • Route aggregation or summary addresses • The Host space • Assign IP addresses based function (.1-.6 network devices)(.9-.14 servers)