Subnet Design and IP Addressing Asst. Prof. Chaiporn Jaikaeo, Ph.D. chaiporn.j@ku.ac.th http://www.cpe.ku.ac.th/~cpj Computer Engineering Department Kasetsart University, Bangkok, Thailand Adapted from the notes by Lami Kaya and lecture slides from Anan Phonphoem © 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved. © The McGraw-Hill Companies, Inc.

Outline IP Address CIDR

Internet Addresses Internet protocol must hide physical network details Application doesn’t care about physical Need address to communicate without knowing underlying network of each other Address should be Unique Uniform addressing scheme Independent to physical networks

Internet Model Revisited router sender router receiver Application Transport Network Data Link Physical Application Transport Network Data Link Physical Network D.L. P.L. Network D.L. P.L. Transmission medium

Network Layer Revisited Data 1.1 5.7 1.1, 1.2, 6.1, 5.7, ... are logical addresses 1.1 1.2 Network 1 R1 6.1 Network 6 6.6 6.3 R3 R2 5.2 Router 3.3 Network 5 5.7 Network 3 3.8

IP Addressing Scheme Unique 32-bit binary number (4 bytes) Assigned to each network interface Used for identify host and communicate Two-level hierarchical address prefix (network ID) – assigned globally suffix (Node/host ID) – assigned locally Address must be coordinated globally Network ID Host ID Prefix Suffix

Internet Classes Traditional addressing scheme Classful Addressing

IP Address Class

IP Address Classes B 25% A 50% C 12.5% D E

No. of Networks / Hosts

IP address in decimal notation 0 0 0 0 1 0 1 1 x 27 26 25 24 23 22 21 20 8 + 2 + 1 = 11

Example: IP address practice Binary Dotted Decimal #1 10011110 01101100 00100000 00010010 158.108.32.18 #2 00001100 00011001 00000001 00010111 12.25.1.23 #3 11001001 01111101 10001001 11010101 201.125.137.213

Class ranges of Internet Address

IP address in decimal notation www.ku.ac.th

Class A example

Class C example

Network Address

Internet Example Network and Host addresses

A Network with Two Levels of Hierarchy Network -> Host

A Network with Three Levels of Hierarchy Network -> Subnet -> Host

Addresses with and without Subnetting

Classful Subnet Masks Class Binary Dotted-Decimal CIDR Notation A 11111111 00000000 00000000 00000000 255.0.0.0 /8 B 11111111 11111111 00000000 00000000 255.255.0.0 /16 C 11111111 11111111 11111111 00000000 255.255.255.0 /24

Subnet Masks

Example: Subnet Mask Find the network ID of each of the following hosts with specified subnet masks: IP: 192.168.5.3 Mask: 255.255.255.0 IP: 172.130.10.20 Mask: 255.255.255.0 IP: 192.168.10.5 Mask: 255.255.255.128 IP: 158.108.228.178 Mask: 255.255.240.0

Outline IP Address CIDR

Classless Inter-Domain Routing CIDR - Classless Inter-Domain Routing Introduced in 1993 to replace classful network design in the Internet To slow the growth of routing tables on routers To help slow the rapid exhaustion of IPv4 addresses No longer restrict network addresses as one or more 8-bit groups

CIDR Notation Specifies mask with prefix size Example: More convenient than binary representation Example: NetID: 158.108.0.0 Subnet Mask: 255.255.0.0 CIDR notation: 158.108.0.0/16

CIDR Host Address

Example: CIDR Notation Convert mask to corresponding prefix size 255.0.0.0 255.192.0.0 255.255.255.252 Convert prefix size to corresponding mask /8 /12 /16 /20 /28

Example: CIDR Notation Find the network ID of each of the following hosts with specified prefix size: IP: 192.168.5.3/24 IP: 172.130.10.20/18

Special IP Addresses Network Address Directed Broadcast Address all hosts = 0; e.g. 158.108.0.0/16 Directed Broadcast Address Broadcast to a specified network all hosts = 1; e.g. 158.108.255.255/16 Limited Broadcast Address Broadcast to local network all 1; e.g. 255.255.255.255 This computer Address all 0; e.g. 0.0.0.0 Loopback Address 127.0.0.0/8  127.x.x.x

Loopback Addresses Allow programmers to test the program logic quickly without needing two computers and without sending packets across a network During loopback testing no packets ever leave a computer the IP software forwards packets from one application to another The loopback address never appears in a packet traveling across a network

Loopback Addresses โปร เซส โปร โปร เซส เซส / A A A Loopback Interface Process A โปร โปร เซส เซส A A A Process B Outgoing packet from Loopback to Process TCP/UDP / 127.0.0.1 127.0.0.1 Loopback Interface IP Incoming packet to Loopback Interface Data Link Physical Other Addresses

Directed Broadcast Address Use for sending to all nodes in class range Class A broadcast example: 10.255.255.255 Class B broadcast example: 158.108.255.255 Class C broadcast example: 202.100.15.255

Special IP Address

Example: Subnet Design You are given an IP address block 12.6.8.0/24 You want to divide this block into subnets Subnet A to serve 28 hosts Subnet B to serve 40 hosts Subnet C to serve 70 hosts List the designed subnets with the following information (1) subnet ID, (2) mask, (3) first usable address, (4) last usable address, (5) directed broadcast address

Example: Subnet Design Design subnetting scheme Subnet C (70 hosts) /25 block (128 addrs) Original /24 block (256 addrs) Subnet A (28 hosts) /26 block (64 addrs) Subnet B (40 hosts) /26 block (64 addrs)

Example: Subnet Design Create summary table Subnet SubNet ID Subnet Mask First Host IP Last Host IP Broadcast Addr C 12.6.8.0 255.255.255.128 12.6.8.1 12.6.8.126 12.6.8.127 A 12.6.8.128 255.255.255.192 12.6.8.129 12.6.8.190 12.6.8.191 B 12.6.8.192 12.6.8.193 12.6.8.254 12.6.8.255