• Objectives• Describe methods of n

• Objectives
• Describe methods of network design unique to TCP/IP networks, including subnetting, CIDR, and address translation
• Explain the differences between public and private TCP/IP networks
• Describe protocols used between mail clients and mail servers, including SMTP, POP3, and IMAP4
• Employ multiple TCP/IP utilities for network discovery and troubleshooting
• Designing TCP/IP-Based Networks
• TCP/IP protocol suite is used for both:
– Internet connectivity
– Transmitting data over private networks
• TCP/IP fundamentals
– IP: routable protocol
• Each interfaces requires unique IP address
• Node may use multiple IP addresses (multihomed device)
– Two IP versions: IPv4 and IPv6
– Networks may assign IP addresses dynamically
• Subnetting
• Separates networks
– Multiple logically defined segments (subnets)
• By geographic locations (floors in a building), departmental boundaries, or technology types
• Subnet traffic separated from other subnet traffic
• Reasons to separate traffic
– Enhance security
– Improve performance
– Simplify troubleshooting

• Subnetting (cont’d.)
• Classful addressing in IPv4
– First and simplest type of IPv4 addressing
– Adheres to network class distinctions
– Recognizes Class A, B, C addresses
• Drawbacks
– Fixed network ID size limits number of network hosts
– Difficult to separate traffic from various parts of a network
• Subnetting (cont’d.)
• Subnetting (cont’d.)
• Subnetting (cont’d.)
• IPv4 subnet mask
– Identifies how network subdivided
– Indicates where network information located
– Subnet mask bits
• 1: corresponding IPv4 address bits contain network information
• 0: corresponding IPv4 address bits contain host information
• Network classes (A, B, & C)
– Associated with default subnet mask
• Subnetting (cont’d.)
• Subnetting (cont’d.)
• ANDing: calculates a host’s network ID given its IPv4 address and subnet mask
– Combining bits
• Bit value of 1 plus another bit value of 1 results in 1
• Bit value of 0 plus any other bit results in 0
– Logic
• 1: “true”
• 0: “false”
• Subnetting (cont’d.)
• Special addresses
– Cannot be assigned to node network interface or used as subnet masks
• Examples of special addresses
– Network ID (example 199.34.89.0)
– Broadcast address (example 199.34.89.255)
• Subnetting (cont’d.)
• IPv4 subnetting techniques
– Subnetting alters classful IPv4 addressing rules
– IP address bits representing host information change to represent network information
• Borrowing bits used for Host IDs
– Reduces number of usable host addresses per subnet
– The number of hosts and subnets available after subnetting is related to how many host information bits you borrow for network information
• Subnetting (cont’d.)
• Calculating IPv4 Subnets
– Formula: 2n −2=Y
• n: number of subnet mask bits needed to switch from 0 to 1
• Y: number of resulting subnets
• Example
– Class C network
• Network ID: 199.34.89.0
• Want to divide into six subnets
• 22 - 2 = 2 No enough we need six subnets
• 23 - 2 = 6 Need to borrow (steal) 3 bits—turn them to 1

• Subnetting (cont’d.)
• Class A, Class B, and Class C networks
– Can be subnetted
• Each class has different number of host information bits usable for subnet information
• Varies depending on network class and the way subnetting is used
• Easiest class to subnet is a Class C
• CIDR (Classless Interdomain Routing)
• Also called classless routing or supernetting
• Provides additional ways of arranging network and host information in an IP address
– Conventional network class distinctions do not exist
• Supernet
– Subnet created by moving subnet boundary left to use more bits for host information (Host IDs)
• CIDR (cont’d.)
• Example: class C range of IPv4 addresses sharing network ID 199.34.89.0
– Need to greatly increase number of default host addresses
• CIDR (cont’d.)
• CIDR notation (or slash notation)
– Shorthand denoting subnet boundary position
– Form
• Network ID followed by forward slash ( / )
• Followed by number of bits used for extended network prefix
– CIDR block
• Forward slash, plus number of bits used for extended network prefix
• Example: /22
• Subnetting in IPv6
• Each ISP can offer customers an entire IPv6 subnet
• Subnetting in IPv6
– Simpler than IPv4
– Classes not used
– Subnet masks not used
• Subnet represented by leftmost 64 bits in an address
• Route prefix
– Slash notation is used
• Internet Gateways
• Combination of software and hardware that enables different network segments to exchange data
• Default gateway