Transcript Slide 1

CIS 1140 Network Fundamentals
Chapter 10 – In Depth TCP/IP Networking
Collected and Compiled
By JD Willard
MCSE, MCSA, Network+,
Microsoft IT Academy Administrator
Computer Information Systems Instructor
Albany 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
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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
IP Addressing Demo
• 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
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
Classful Addressing in IPv4
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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
IP addresses and their classes
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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 Mask
1 Convert the Number of Segments to Binary
2 Count the Number of Required Bits
3 Convert the Required Number of Bits to Decimal
(High Order)
Example of Class B Address
Number of Subnets
6
Binary Value
0 0 0 0 0 1 1 0
(3 Bits)
4+2 = 6
Convert to Decimal
Subnet Mask
Subnet Masks Demo
11111111
255
11111111
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255
11100000 00000000
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224
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0
Solutions for Masks Demo
IPv4 Subnet Masks
Default IPv4 subnet masks
• Network class
– Associated with default subnet mask
Determining the Destination of a Packet
(ANDing)
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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.
10011111
Subnet Mask 11111111
11100000
11111111
00000111 10000001
00000000 00000000
10011111
11100000
00000000 00000000
IP Address
Result
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 Demo
Subnetting Shortcuts Demo
Subnet Numbers Demo
Borrowing Bits Demo
Borrowing Bits Demo
Solutions for Borrowing 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: 2n2=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 IDs
1
255
255
224
0
11111111 11111111 11100000 00000000
Address Ranges Demo
Solutions for Ranges Demo
00000000 = 0
00100000 = 32
01000000 = 64
01100000 = 96
10000000 = 128
10100000 = 160
11000000 = 192
11100000 = 224
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Shortcut to Defining Subnet IDs
1 List the Number of Bits (High Order) Used for
Subnet Mask
11000000
2 Convert the Bit with the Lowest Value to Decimal 64
3 Increment the Value for Each Bit Combination
0
+ 64
= 64
+ 64
= 128
+ 64
192
w.x.64.1
w.x.127.254
w.x.128.1
w.x.191.254
Defining Host IDs for a Subnet
Subnet IDs
00000000 = 0
00100000 = 32
01000000 = 64
01100000 = 96
10000000 = 128
10100000 = 160
11000000 = 192
11100000 = 224
Host ID Range
Invalid
x.y.32.1 –
x.y.64.1 –
x.y.96.1 –
x.y.128.1 –
x.y.160.1 –
x.y.192.1 –
Invalid
x.y.63.254
x.y.95.254
x.y.127.254
x.y.159.254
x.y.191.254
x.y.223.254
• 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
A router connecting several subnets
Practice 1 Demo
Practice 2 Demo
Solutions for Practice 1 Demo
Solutions for Practice 2 Demo
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
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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 Internetrecognized 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)
– 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
masquerading
Internet-valid IP address
might be assigned to any
client’s outgoing
transmission
SNAT (Static Network Address Translation)
Address Translation
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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)
The Concepts of NAT & PAT Demo
Internet Connection Sharing 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)
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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)
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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
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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
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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
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Utility used on UNIX and Linux systems
– Modify TCP/IP network interface settings, release and renew DHCPassigned 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
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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
• 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
Using DIG in Unix Demo
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
WHOIS Demo
– e.g., www.arin.net
Traceroute (Tracert)
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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)
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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
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Route utility
– Allows viewing of host’s routing table
UNIX or Linux system
– Type route and press Enter
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Windows-based system
– Type route print and press Enter
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Cisco-brand router
– Type show ip route and press Enter
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Route command
– Add, delete, modify routes
Route command help
– UNIX or Linux system
• Type man route and press Enter
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– Windows system
• Type route ? and press Enter
The 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