CIS 1140 Network FundamentalsChapter 10 – In Depth TCP/IP Networking

Collected and CompiledBy JD WillardMCSE, MCSA, Network+, Microsoft IT Academy AdministratorComputer Information Systems InstructorAlbany Technical College

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Objectives• Understand 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 use

– Public Internet connectivity– Private connection data transmission

• TCP/IP fundamentals– IP: routable protocol

• Interfaces requires unique IP address• Node may use multiple IP addresses

– Two IP versions: IPv4 and IPv6• IPv4: older; more common

• IPv4 addresses– Four 8-bit octets

• Binary or dotted decimal• Network host name assignment

– Dynamic using DHCP– Static

• Network classes: A, B, C, D, E – Class D, E addresses reserved– Node’s network class provides information about segment network node belongs to

IP Addressing Demo

Subnetting• Separates network

– Multiple logically defined segments (subnets)• Geographic locations, departmental boundaries,

technology types

• Subnet traffic separated from other subnet traffic

• Reasons to separate traffic– Enhance security– Improve performance– Simplify troubleshooting

• First, simplest IPv4 addressing type

• Adheres to network class distinctions

• Recognizes Class A, B, C addresses

• Fixed network ID size ultimately limits number of hosts a network can include

• Difficult to separate traffic from various parts of a network

Address Classes Demo

Classful Addressing in IPv4

Classful Addressing in IPv4

IP addresses and their classes

• Network information (network ID)– First 8 bits in Class A address– First 16 bits in Class B address– First 24 bits in a Class C address

• Host information– Last 24 bits in Class A address– Last 16 bits in Class B address– Last 8 bits in Class C address

Classful Addressing (continued)

Example IP addresses with classful addressing

Subnet Masks• Subnetting depends on subnet masks to identify

how a network is subdivided– Indicates where network information is

located in an IP address– “1” bits indicate corresponding bits in IP

address contain network information– “0” bits indicate corresponding bits in IP

address contain host information• To calculate host’s network ID given IP address

and subnet mask, perform ANDing

Defining a Subnet MaskConvert the Number of Segments to Binary

Count the Number of Required Bits

Convert the Required Number of Bits to Decimal (High Order)

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Example of Class B Address

Number of SubnetsNumber of Subnets

Binary ValueBinary Value

Convert to DecimalConvert to Decimal

6

0 0 0 0 0 1 1 0

= 6

(3 Bits)

4+2

255 . 255 . 224 . 0

11111111 11111111 11100000 00000000

Subnet MaskSubnet Mask

Subnet Masks Demo Solutions for Masks Demo

IPv4 Subnet Masks

• Network class– Associated with default subnet mask

Default IPv4 subnet masks

Determining the Destination of a Packet (ANDing)

10011111 11100000 00000111 10000001

11111111 11111111 00000000 00000000

10011111 11100000 00000111 10000001

11111111 11111111 00000000 00000000

10011111 11100000 00000000 0000000010011111 11100000 00000000 00000000

IP Address

Subnet Mask

IP Address

Subnet Mask

ResultResult

• Local and Destination Host’s Subnet Masks Are ANDed• ANDing

– 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

– ANDing logic• 1: “true”, 0: “false

– If ANDed results of source and destination hosts match, the destination is local. – If ANDed results of source and destination hosts do not match, the destination

is remote and the packet is sent to the default gateway.

ANDing Demo

Reserved Addresses• Certain types of IP addresses reserved for special

functions• Cannot be assigned to node network interface; used as

subnet masks• Network ID

– Bits available for host information set to 0– Classful IPv4 addressing network ID ends with 0 octet– Subnetting allows network ID with other decimal

values in last octet(s)• Broadcast address

– Octet(s) representing host information equal all 1s– Decimal notation: 255

Addressing Rules; the Logical AND Operator Demo

IPv4 Subnetting Techniques• Subnetting breaks classful IPv4

addressing rules– Some bits that in classful addressing would

represent host information are changed to represent network information

– Reduces the number of usable host addresses per subnet

– Hosts, subnets available after subnetting related to host information bits borrowed

Subnetting Shortcuts Demo Borrowing Bits Demo Subnetting Demo Borrowing Bits Demo Solutions for Borrowing Demo Subnet Numbers Demo

Implementing Subnetting• Determine the Number of Required

Network IDs– One for each subnet– One for each wide-area

network connection• Determine the Number of Required

Host IDs per Subnet– One for each TCP/IP host– One for each router interface

• Define One Subnet Mask Based on Requirements

• Define a Unique Subnet ID for Each Physical Segment Based on the Subnet Mask

• Define Valid Host IDs for Each Subnet Based on the Subnet ID

Table 1 : Class B subnet masks

Table 2 : Class C subnet masks

Calculating IPv4 Subnets• Formula for determining how to modify a default subnet mask: 2n-2=Y

– n = number of bits in subnet mask that must be switched from 0 to 1

– Y = number of subnets that result• Extended network prefix: Additional bits used for subnet information

plus existing network ID• 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• LAN subnetting

– LAN’s devices interpret device subnetting information– External routers

• Need network portion of device IP address

Defining Subnet IDs255 255 224 0

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0

00000000 = 000100000 = 3201000000 = 6401100000 = 9610000000 = 12810100000 = 16011000000 = 19211100000 = 224

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Address Ranges Demo

Solutions for Ranges Demo

Shortcut to Defining Subnet IDsList the Number of Bits (High Order) Used for Subnet Mask

Convert the Bit with the Lowest Value to Decimal

Increment the Value for Each Bit Combination

1100000011000000

6464

0+ 64= 64+ 64= 128+ 64

192

w.x.64.1 w.x.127.254

w.x.128.1 w.x.191.254

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Defining Host IDs for a SubnetSubnet IDsSubnet IDs Host ID RangeHost ID Range

Invalidx.y.32.1 – x.y.63.254x.y.64.1 – x.y.95.254x.y.96.1 – x.y.127.254x.y.128.1 – x.y.159.254x.y.160.1 – x.y.191.254x.y.192.1 – x.y.223.254Invalid

Invalidx.y.32.1 – x.y.63.254x.y.64.1 – x.y.95.254x.y.96.1 – x.y.127.254x.y.128.1 – x.y.159.254x.y.160.1 – x.y.191.254x.y.192.1 – x.y.223.254Invalid

00000000 = 000100000 = 3201000000 = 6401100000 = 9610000000 = 12810100000 = 16011000000 = 19211100000 = 224

00000000 = 000100000 = 3201000000 = 6401100000 = 9610000000 = 12810100000 = 16011000000 = 19211100000 = 224

• Each Subnet ID Indicates the Beginning Value in a Range• The Ending Value Is One Less Than the Beginning Value

of the Next Subnet ID

Calculating Subnets

Practice 1 Demo Solutions for Practice 1 Demo

Practice 2 Demo Solutions for Practice 2 Demo

A router connecting several subnets

CIDR (Classless Interdomain Routing)

• Also called classless routing or supernetting• Provides additional ways of arranging network and

host information in an IP address• Not exclusive of subnetting

– 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

Classless Internet Domain Routing Demo

CIDR• 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: class C range of IPv4 addresses sharing network ID

199.34.89.0– Need to greatly increase number of default host addresses

Calculating a host’s network ID on a supernetted network

Subnetting/Supernetting Demo

Internet Gateways• Gateway

– Combination of software and hardware– Facilitates communication between different networks, subnets

• Default gateway– Every device on a TCP/IP-based network has a default gateway– First interprets its outbound requests to other subnets– Then interprets its inbound requests from other subnets– Each node on network has one default gateway– May be network interface on a router

• Must maintain routing tables as well• Core gateways make up the Internet backbone• Network nodes

– Allowed one default gateway• Assigned manually, automatically (DHCP)

Internet Gateways• Gateway interface on router

– All data not meant for the local subnet is sent to this router

– Advantages• One router can

supply multiple gateways

• Gateway assigned own IP address

• Default gateway connections– Multiple internal networks– Internal network with

external networks• WANs, Internet

– Router used as gateway• Must maintain routing

tables

The use of default gateways

Address Translation• Public network

– Any user may access• Little or no restrictions

• Private network– Access restricted

• Clients, machines with proper credentials– Hiding IP addresses

• Provides more flexibility in assigning addresses• NAT (Network Address Translation)

– Gateway replaces client’s private IP address with Internet-recognized IP address

• Reasons for using address translation– Overcome IPv4 address quantity limitations– Add marginal security to private network when connected to public

network– Develop network addressing scheme

NAT Demo

Address Translation

SNAT (Static Network Address Translation)

• SNAT (Static Network Address Translation)– Client associated with

one private IP address, one public IP address

• Never changes– Useful when operating

mail server• DNAT (Dynamic Network

Address Translation)Also called IP

masqueradingInternet-valid IP address

might be assigned to any client’s outgoing transmission

Address Translation• PAT (Port Address Translation)

– Each client session with server on Internet assigned separate TCP port number

• Client server request datagram contains port number

– Internet server responds with datagram’s destination address including same port number

• NAT– Separates private, public

transmissions on TCP/IP network• Gateways conduct network translation

– Most networks use router• Gateway might operate on network host

– Windows operating systems• ICS (Internet Connection

Sharing)

Internet Connection Sharing Demo

The Concepts of NAT & PAT Demo

TCP/IP Mail Services• E-mail

– Most frequently used Internet services– Functions

• Mail delivery, storage, pickup

• Mail servers– Communicate with other mail servers– Deliver messages, send, receive, store

messages

• Mail clients – Send messages to; retrieve messages from mail

servers

SMTP (Simple Mail Transfer Protocol)

• Protocol responsible for moving messages– From one mail server to another

• Over TCP/IP-based networks• Operates at Application layer

– Relies on TCP at Transport layer• Operates from port 25• Provides basis for Internet e-mail service

– Relies on higher-level programs for its instructions• Services provide friendly, sophisticated mail interfaces• Simple subprotocol

– Transports mail, holds it in a queue• Client e-mail configuration

– Identify user’s SMTP server• Use DNS: Identify name only

– No port definition• Client workstation, server assume port 25

MIME (Multipurpose Internet Mail Extensions)

• SMTP drawback: 1000 ASCII character limit• MIME standard encodes, interprets binary files,

images, video, non-ASCII character sets within e-mail message– Identifies each mail message element

according to content type• Text, graphics, audio, video, multipart

• Does not replace SMTP– Works in conjunction with it

• Encodes different content types– Fools SMTP

POP (Post Office Protocol)

• Application layer protocol– Retrieve messages from mail server

• POP3 (Post Office Protocol, version 3)– Current, popular version– Relies on TCP, operates over port 110– Store-and-forward type of service

• Advantages– Minimizes server resources

• Mail deleted from server after retrieval• Disadvantage for mobile users

– Mail server, client applications support POP3

IMAP (Internet Message Access Protocol)• More sophisticated alternative to POP3• IMAP4: current version• Advantages

– Replace POP3 without having to change e-mail programs– E-mail stays on server after retrieval

• Good for mobile users• Features

– Users can retrieve all or portion of mail message– Users can review messages and delete them

• While messages remain on server– Users can create sophisticated methods of organizing messages on server– Users can share mailbox in central location

• Disadvantages– Requires more storage space, processing resources than POP servers– Network managers must watch user allocations closely– IMAP4 server failure

• Users cannot access mail

Additional TCP/IP Utilities

• TCP/IP transmission process– Many points of failure

• Increase with network size, distance• TCP/IP comes with complete set of utilities that can help to

track down most TCP/IP-related problems– Help discover information about node, network– e.g., Ping, Telnet, ARP

• Nearly all TCP/IP utilities can be accessed from command prompt on any type of server or client running TCP/IP– Syntax may differ depending on OS– Options may differ according to OS

Ipconfig• TCP/IP administration utility for use with Windows NT, 2000, XP, and

Server 2003 OSs– Provides information about network adapter’s IP address, subnet mask, and

default gateway• Commonly used switches:

– /? displays list of available switches– /all displays complete TCP/IP configuration information for each network

interface on device– /release releases DHCP-assigned addresses for all network interfaces– /renew renews DHCP-assigned addresses for all network interfaces

IPConfig, Ifconfig,Winipcfg Demo

Ifconfig• Utility used on UNIX and Linux systems

– Modify TCP/IP network interface settings, release and renew DHCP-assigned addresses, check TCP/IP setting status

– Runs at UNIX, Linux system starts

• Establishes computer TCP/IP configuration

• Used alone or with switches

– Uses hyphen ( - ) before some switches

– No preceding character for other switches

Detailed information available through ifconfig

Netstat

• Displays TCP/IP statistics and details about TCP/IP components and connections on a host– Port on which a particular TCP/IP service is running– Network connections currently established– Number of packets handled by network interface since

activation– Number of data errors

NETSTAT Demo

Nbtstat• NetBIOS

– Protocol runs in Session and Transport layers

– Associates NetBIOS names with workstations

– Not routable• Can be made routable by

encapsulation• Nbtstat utility

– Provides information about NetBIOS statistics

– Resolves NetBIOS names to IP addresses

– Useful on Windows-based operating systems and NetBIOS

• Limited use as TCP/IP diagnostic utility

NBTSTAT Demo

Hostname, Host

• Hostname utility– Provides client’s host name

• Administrator may change

• Host utility– Learn IP address from host name– No switches: returns host IP address or host

name

Nslookup• Query DNS database from any network computer and

find host name of a device by specifying its IP address, or vice versa– Provides host’s IP address, primary DNS server

name, and address holding record for this name– Many options (switches)– Verify host configured correctly; troubleshoot DNS

resolution problems

Using NSLOOKUP Demo

Dig

Using DIG in Unix Demo

• Domain information groper• Similar to nslookup

– Query DNS database– Find specific IP address host name

• Useful for diagnosing DNS problems• Dig utility provides more detailed information

than nslookup• Flexible: two dozen switches• Included with UNIX, Linux operating systems• Windows system: must obtain third party code

Dig

Output of a simple dig command

Whois• Query DNS registration database and obtain information about a

domain• Troubleshoot network problems• Syntax

– whois xxx.yy•xxx.yy is second-level domain name

– Who is domain registered to?– Technical person responsible for domain?– Hosting entity?– DNS Server addresses?

• Must install software to use on Windows systems• Web-based alternatives exist

– e.g., www.arin.net

WHOIS Demo

Traceroute (Tracert)• Windows-based systems: tracert

• Linux systems: tracepath• Uses ICMP to trace path from one node to another

– Identifies all intermediate hops– Useful for determining router or subnet connectivity problems– Transmits series of UDP datagrams to specified destination

– Using either IP address or host name

• To identify destination• Increases TTL as path is discovered

• Traceroute may stop before completing– Device problem on path– Device does not accept ICMP transmissions

• Often indicates firewall

Using TraceRT Demo

Mtr (my traceroute)• UNIX, Linux operating systems

– Route discovery, analysis utility– Combines ping, traceroute functions

• Output: easy-to-read chart• Simplest form

– mtr ip_address or mtr host_name• Run continuously• Stop with Ctrl+C or add limiting option to command

• Number of switches refine functioning, output• Results misleading

– If devices prevented from responding to ICMP traffic

Mtr (my traceroute)• Windows XP, Vista, Server 2003, Server 2008

– Pathping program as command-line utility

– Simile switches as mtr– Pathping output differs slightly

• Displays path first

• Then issues hundreds of ICMP ECHO requests before revealing reply, packet loss statistics

Route• Route utility

– Allows viewing of host’s routing table• UNIX or Linux system

– Type route and press Enter• Windows-based system

– Type route print and press Enter• Cisco-brand router

– Type show ip route and press Enter

• Route command– Add, delete, modify routes

• Route command help– UNIX or Linux system

• Type man route and press Enter– Windows system

• Type route ? and press EnterThe Route Command Demo

Summary

• This chapter covered:– Designing TCP/IP-Based Networks– Subnetting– CIDR– Internet gateways– Address translation– TCP mail services– Utility commands

The End