Cisco CCNA v3.0

Semester 1Semester 1Chapter 9Chapter 9

Prepared by: Terren L. BichardPrepared by: Terren L. Bichard

History and Future of TCP/IP

The U.S. Department of Defense (DoD) The U.S. Department of Defense (DoD) created the TCP/IP reference modelcreated the TCP/IP reference model It wanted a network that could survive It wanted a network that could survive

any conditions.any conditions.

TCP/IP Layered Model

ApplicationApplication TransportTransport InternetInternet Network AccessNetwork Access

TCP/IP v4

Standardized in September of 1981Standardized in September of 1981 IPv4 addresses are 32 bits longIPv4 addresses are 32 bits long

Written in dotted decimalWritten in dotted decimal Separated by periods.Separated by periods.

i.e. 192.168.52.34i.e. 192.168.52.34

TCP/IP v6

128 bits long128 bits long Written in hexadecimalWritten in hexadecimal Separated by colonsSeparated by colons

Colons separate 16-bit fields. Colons separate 16-bit fields. Leading zeros can be omitted in Leading zeros can be omitted in

each field.each field.• i.e. the field :0003: is written :3:i.e. the field :0003: is written :3:

TCP/IP v6.0 Standardized in 1992Standardized in 1992

Often called IpngOften called IpngWas supported by the Internet Engineering Was supported by the Internet Engineering

Task Force (IETF)Task Force (IETF)IPv6 has not gained wide implementation, IPv6 has not gained wide implementation,

but it has been released by most vendors of but it has been released by most vendors of networking equipment networking equipment

Will eventually become the dominant Will eventually become the dominant standard. standard.

Application Layer The application layer handles:The application layer handles:

high-level protocolshigh-level protocols issues of representationissues of representation EncodingEncoding dialog controldialog control

The TCP/IP protocol suite combines all The TCP/IP protocol suite combines all application related issues into one layer and application related issues into one layer and assures this data is properly packaged before assures this data is properly packaged before passing it on to the next layer.passing it on to the next layer.

Application Layer

In addition to Internet and transport layer In addition to Internet and transport layer specifications, such as IP and TCP, the specifications, such as IP and TCP, the TCP/IP model also includes specifications TCP/IP model also includes specifications for common applications. for common applications.

Has protocols to support file transfer, e-Has protocols to support file transfer, e-mail, and remote login.mail, and remote login.

Application Layer Also supports:Also supports:

File Transfer Protocol (FTP)File Transfer Protocol (FTP) Trivial File Transfer Protocol (TFTP)Trivial File Transfer Protocol (TFTP) Network File System (NFS)Network File System (NFS) Simple Mail Transfer Protocol (SMTP)Simple Mail Transfer Protocol (SMTP) Terminal emulation (Telnet)Terminal emulation (Telnet) Simple Network Management Protocol Simple Network Management Protocol

(SNMP)(SNMP) Domain Name System (DNS)Domain Name System (DNS)

File Transfer Protocol (FTP)

File Transfer Protocol (FTP)File Transfer Protocol (FTP) – FTP is a – FTP is a reliable, connection-oriented service that reliable, connection-oriented service that uses TCP to transfer files between systems uses TCP to transfer files between systems that support FTP. that support FTP.

It supports bi-directional binary file and It supports bi-directional binary file and ASCII file transfers.ASCII file transfers.

Trivial File Transfer Protocol (TFTP)

Trivial File Transfer Protocol (TFTP)Trivial File Transfer Protocol (TFTP) – – TFTP is a connectionless service.TFTP is a connectionless service.

Uses the User Datagram Protocol (UDP). Uses the User Datagram Protocol (UDP). TFTP is used on the router to transfer TFTP is used on the router to transfer

configuration files and Cisco IOS images, and configuration files and Cisco IOS images, and to transfer files between systems that support to transfer files between systems that support TFTP. TFTP.

It is useful in some LANs because it operates It is useful in some LANs because it operates faster than FTP in a stable environment. faster than FTP in a stable environment.

Network File System (NFS) Network File System (NFS)Network File System (NFS) – NFS is a – NFS is a

distributed file system protocol suitedistributed file system protocol suiteDeveloped by Sun MicrosystemsDeveloped by Sun Microsystems

• Allows file access to a remote Allows file access to a remote storage device such as a hard disk storage device such as a hard disk across a network. across a network.

Simple Mail Transfer Protocol Simple Mail Transfer Protocol (SMTP)Simple Mail Transfer Protocol (SMTP)

– SMTP administers the transmission of – SMTP administers the transmission of e-mail over computer networks. e-mail over computer networks.

It does not provide support for It does not provide support for transmission of data other than plaintext. transmission of data other than plaintext.

Terminal emulation (Telnet) Terminal emulation (Telnet)Terminal emulation (Telnet) – Telnet – Telnet

provides the capability to remotely access provides the capability to remotely access another computer.another computer.

Enables a user to log in to an Internet host and Enables a user to log in to an Internet host and execute commands.execute commands.

A Telnet client is referred to as a local host. A Telnet client is referred to as a local host. A Telnet server is referred to as a remote host. A Telnet server is referred to as a remote host.

Simple Network Management Protocol (SNMP)

Simple Network Management Protocol Simple Network Management Protocol (SNMP)(SNMP) – SNMP is a protocol that – SNMP is a protocol that provides a way to monitor and control provides a way to monitor and control network devicesnetwork devices

Manage configurations, statistics Manage configurations, statistics collection, performance, and securitycollection, performance, and security

Domain Name System (DNS) Domain Name System (DNS)Domain Name System (DNS) – DNS is – DNS is

a system used on the Internet for a system used on the Internet for translating names of domains and their translating names of domains and their publicly advertised network nodes into IP publicly advertised network nodes into IP addresses.addresses.

Transport Layer Provides transport services from the source host to the Provides transport services from the source host to the

destination host.destination host. End-to-end control, provided by sliding windows and End-to-end control, provided by sliding windows and

reliability in sequencing numbers and acknowledgments reliability in sequencing numbers and acknowledgments Constitutes a logical connection between the endpoints of Constitutes a logical connection between the endpoints of

the networkthe network the sending host and the receiving hostthe sending host and the receiving host

Transport protocols segment and reassemble upper-layer Transport protocols segment and reassemble upper-layer applications into the same data stream between endpoints.applications into the same data stream between endpoints.

The transport layer data stream provides end-to-end The transport layer data stream provides end-to-end transport services. transport services.

Transport Layer Transport services include all the following services: Transport services include all the following services: TCP and UDPTCP and UDP

Segmenting upper-layer application data Segmenting upper-layer application data Sending segments from one end device to Sending segments from one end device to

another end device another end device TCP only TCP only

Establishing end-to-end operations Establishing end-to-end operations Flow control provided by sliding windows Flow control provided by sliding windows Reliability provided by sequence numbers and Reliability provided by sequence numbers and

acknowledgments acknowledgments

Internet Layer The purpose of the Internet layer is to select The purpose of the Internet layer is to select

the best path through the network for the best path through the network for packets to travel.packets to travel.

The main protocol that functions at this The main protocol that functions at this layer is the Internet Protocol (IP). layer is the Internet Protocol (IP).

Best path determination and packet Best path determination and packet switching occur at this layer.switching occur at this layer. Path and switching done by the router Path and switching done by the router

Internet Layer The following protocols operate at the TCP/IP Internet layer:The following protocols operate at the TCP/IP Internet layer:

IP provides connectionless, best-effort delivery routing of IP provides connectionless, best-effort delivery routing of packets. packets.

Internet Control Message Protocol (ICMP) Internet Control Message Protocol (ICMP) provides control and messaging capabilities. provides control and messaging capabilities.

Address Resolution Protocol (ARP)Address Resolution Protocol (ARP)determines the data link layer addressdetermines the data link layer addressMAC address, for known IP addresses. MAC address, for known IP addresses.

Reverse Address Resolution Protocol (RARP)Reverse Address Resolution Protocol (RARP)determines IP addresses when the MAC determines IP addresses when the MAC

address address is known.is known.

Internet Layer IP performs the following operations:IP performs the following operations:

Defines a packet and an addressing schemeDefines a packet and an addressing scheme Transfers data between the internet layer and Transfers data between the internet layer and

network access layersnetwork access layers Routes packets to remote hostsRoutes packets to remote hosts

IP is considered an unreliable protocol.IP is considered an unreliable protocol. Error checking is done by another layerError checking is done by another layer

Handled by upper layer Handled by upper layer

Network Access Layer The network access layer is also called the host-to-The network access layer is also called the host-to-

network layer. network layer. The network access layer is the layer that is The network access layer is the layer that is

concerned with all of the issues that an IP packet concerned with all of the issues that an IP packet requires to actually make a physical link to the requires to actually make a physical link to the network media. network media. Includes the LAN and WAN technology detailsIncludes the LAN and WAN technology details All the details contained in the OSI physical All the details contained in the OSI physical

and data-link layers. and data-link layers.

Network Access Layer Drivers for software applications, modem cards Drivers for software applications, modem cards

and other devices operate at the network access and other devices operate at the network access layer. layer.

Defines the procedures for interfacing with the Defines the procedures for interfacing with the network hardware and accessing the transmission network hardware and accessing the transmission medium. medium.

Modem protocol standards such as Serial Line Modem protocol standards such as Serial Line Internet Protocol (SLIP) and Point-to-Point Internet Protocol (SLIP) and Point-to-Point Protocol (PPP) provide network access through a Protocol (PPP) provide network access through a modem connection. modem connection.

Network Access Layer

Network Access Layer functions include Network Access Layer functions include mapping IP addresses to physical hardware mapping IP addresses to physical hardware addresses and encapsulation of IP packets addresses and encapsulation of IP packets into frames. into frames.

TCP/IP vs OSI

Similarities Both have layers Both have layers Both have application layers, though they include Both have application layers, though they include

very different services very different services Both have comparable transport and network Both have comparable transport and network

layers layers Packet-switched, not circuit-switched, technology Packet-switched, not circuit-switched, technology

is assumed is assumed Networking professionals need to know both Networking professionals need to know both

modelsmodels

Differences TCP/IP combines the presentation and session TCP/IP combines the presentation and session

layer into its application layer layer into its application layer TCP/IP combines the OSI data link and physical TCP/IP combines the OSI data link and physical

layers into one layer layers into one layer TCP/IP appears simpler because it has fewer TCP/IP appears simpler because it has fewer

layers layers TCP/IP transport layer using UDP does not always TCP/IP transport layer using UDP does not always

guarantee reliable delivery of packets as the guarantee reliable delivery of packets as the transport layer in the OSI model does transport layer in the OSI model does

Internet Architecture LANs are smaller networks limited in geographic LANs are smaller networks limited in geographic

area. area. Many LANs connected together allow the Internet Many LANs connected together allow the Internet

to function. to function. LANs have limitations in scale. LANs have limitations in scale. Although there have been technological advances Although there have been technological advances

to improve the speed of communications, such as to improve the speed of communications, such as Metro Optical, Gigabit, and 10-Gigabit Ethernet, Metro Optical, Gigabit, and 10-Gigabit Ethernet, distance is still a problem.distance is still a problem.

Internet Addresses IP AddressingFor any two systems to communicateFor any two systems to communicate

Be able to identify each other Be able to identify each other Locate each otherLocate each other

i.e. addresses of houses i.e. addresses of houses • State, City, Street, AddressState, City, Street, Address

IP Addressing

Each device on a LAN must have a unique Each device on a LAN must have a unique identifying number.identifying number. IP Address – Layer 3, Logical AddressIP Address – Layer 3, Logical Address MAC Address – Layer 2, Physical MAC Address – Layer 2, Physical

AddressAddress

IP Address

32-bit address with 1s and 0s.32-bit address with 1s and 0s. To make IP addresses easier to read it is To make IP addresses easier to read it is

written in 4 decimal numbers separated by written in 4 decimal numbers separated by periods. i.e. periods. i.e. 192.168.1.2192.168.1.2 Called dotted decimalCalled dotted decimal

Decimal & Binary Conversions

When converting a decimal number to binary, the biggest power of two that will fit into the decimal number must be determined.•Start by calculating a couple of examples, the first being 6,783. •Since this number is greater than 255, the largest value possible in a single byte, two bytes will be used. •Start calculating from 215. •The binary equivalent of 6,783 is 00011010 01111111.

IPv4 Addressing Router forwards packets from the Router forwards packets from the

originating network to the destination originating network to the destination network using the IP protocol. network using the IP protocol.

Packets must include an identifier for both Packets must include an identifier for both the source and destination networks.the source and destination networks.

Using the IP address of destination network, Using the IP address of destination network, a router can deliver a packet to the correct a router can deliver a packet to the correct network. network.

IPv4 Addressing This system works in much the same way as the This system works in much the same way as the

national postal system. national postal system. When the mail is routed, it must first be delivered When the mail is routed, it must first be delivered

to the post office at the destination city using the to the post office at the destination city using the zip code. zip code.

That post office then must locate the final That post office then must locate the final destination in that city using the street address. destination in that city using the street address.

This is a two-step process. This is a two-step process.

IPv4 Addressing Every IP address has two parts.Every IP address has two parts.

NetworkNetwork HostHost

Each of the 4 octets range from 0 to 255. Each of the 4 octets range from 0 to 255. Each one of the octets breaks down into 256 Each one of the octets breaks down into 256

subgroups subgroups • They break down into another 256 They break down into another 256

subgroups with 256 addresses in each. subgroups with 256 addresses in each.

IPv4 Addressing This kind of address is called a hierarchical address, This kind of address is called a hierarchical address,

because it contains different levels.because it contains different levels. An IP address combines these two identifiers into one An IP address combines these two identifiers into one

number. number. Must be a unique numberMust be a unique number

Duplicate addresses would make routing Duplicate addresses would make routing impossible.impossible.

The first part identifies the network address. The first part identifies the network address. The second part, identifies which particular machine The second part, identifies which particular machine

it is on the network.it is on the network.

IPv4 Addressing IP addresses are divided into classes to define the IP addresses are divided into classes to define the

large, medium, and small networks. large, medium, and small networks. Class A addresses are assigned to larger networks. Class A addresses are assigned to larger networks. Class B addresses are used for medium-sized Class B addresses are used for medium-sized

networks.networks. Class C for small networks.Class C for small networks.

The first step in determining which part of the address The first step in determining which part of the address identifies the network and which part identifies the identifies the network and which part identifies the host is identifying the class of an IP address. host is identifying the class of an IP address.

IPv4 Addressing To accommodate different size networks and aid To accommodate different size networks and aid

in classifying these networks, IP addresses are in classifying these networks, IP addresses are divided into groups called classes.divided into groups called classes.

This is known as classful addressing. This is known as classful addressing. Each complete 32-bit IP address is broken Each complete 32-bit IP address is broken

down into a network part and a host part.down into a network part and a host part. A bit or bit sequence at the start of each address A bit or bit sequence at the start of each address

determines the class of the address. determines the class of the address. There are five IP address classes There are five IP address classes

IPv4 Addressing (Class A) The Class A address designed to support The Class A address designed to support

extremely large networksextremely large networks 16 million + host addresses16 million + host addresses Class A IP addresses use only the first Class A IP addresses use only the first

octet to indicate the network address.octet to indicate the network address. The remaining three octets provide for The remaining three octets provide for

host addresses. host addresses. 124124.15.67.93.15.67.93

IPv4 Addressing (Class A) The first bit of a Class A address is always 0. The first bit of a Class A address is always 0. With that first bit a 0, the lowest number that can be With that first bit a 0, the lowest number that can be

represented is 00000000represented is 00000000 decimal 0decimal 0

The highest number that can be represented is The highest number that can be represented is 0111111101111111 decimal 127decimal 127

The numbers 0 and 127 are reserved The numbers 0 and 127 are reserved Any address that starts with a value between 1 and Any address that starts with a value between 1 and

126 in the first octet is a Class A address.126 in the first octet is a Class A address.

IPv4 Addressing (Loopback)

The 127.0.0.0 network is reserved for The 127.0.0.0 network is reserved for loopback testing. loopback testing.

Routers or local machines can use this Routers or local machines can use this address to send packets back to themselves. address to send packets back to themselves.

This number cannot be assigned to a This number cannot be assigned to a networknetwork

IPv4 Addressing (Class B)

The Class B address was designed to The Class B address was designed to support the needs of moderate to large-sized support the needs of moderate to large-sized networks.networks.

Class B IP address uses the first two of the Class B IP address uses the first two of the four octets to indicate the network address.four octets to indicate the network address.

The other two octets specify host addresses.The other two octets specify host addresses. 192.165192.165..56.8956.89

IPv4 Addressing (Class B) The first two bits of the first octet of a Class B The first two bits of the first octet of a Class B

address are always 10.address are always 10. The remaining six bits may be populated with either The remaining six bits may be populated with either

1s or 0s.1s or 0s. The lowest number that can be represented with a The lowest number that can be represented with a

Class B address is 10000000Class B address is 10000000 Decimal 128Decimal 128

The highest number that can be represented is The highest number that can be represented is 1011111110111111 Decimal 191 Decimal 191

IPv4 Addressing (Class C) The Class C address space is the most commonly used The Class C address space is the most commonly used

of the original address classes.of the original address classes. Intended to support small networks with a maximum Intended to support small networks with a maximum

of 254 hosts. of 254 hosts. A Class C address begins with binary 110.A Class C address begins with binary 110. The lowest number that can be represented is The lowest number that can be represented is

1100000011000000 decimal 192decimal 192

The highest number that can be represented is The highest number that can be represented is 1101111111011111 decimal 223decimal 223

IPv4 Addressing (Class D) The Class D address class was created to The Class D address class was created to

enable multicasting in an IP address.enable multicasting in an IP address. A unique network address that directs A unique network address that directs

packets with that destination address to packets with that destination address to predefined groups of IP addresses.predefined groups of IP addresses.

A single station can simultaneously A single station can simultaneously transmit a single stream of data to transmit a single stream of data to multiple recipients. multiple recipients.

IPv4 Addressing (Class D) The Class D address space, much like the other The Class D address space, much like the other

address spaces, is mathematically constrained. address spaces, is mathematically constrained. The first four bits of a Class D address must be The first four bits of a Class D address must be

1110. 1110. The first octet range for Class D addresses is The first octet range for Class D addresses is

11100000 to 11101111, or 224 to 239.11100000 to 11101111, or 224 to 239. An IP address that starts with a value in the range An IP address that starts with a value in the range

of 224 to 239 in the first octet is a Class D of 224 to 239 in the first octet is a Class D address. address.

IPv4 Addressing (Class E) A Class E address has been defined.A Class E address has been defined. However, the Internet Engineering Task Force However, the Internet Engineering Task Force

(IETF) reserves these addresses for its own research. (IETF) reserves these addresses for its own research. No Class E addresses have been released for use in No Class E addresses have been released for use in

the Internet. the Internet. The first four bits of a Class E address are always set The first four bits of a Class E address are always set

to 1s. to 1s. The first octet range for Class E addresses is The first octet range for Class E addresses is

11110000 to 11111111, or 240 to 255.11110000 to 11111111, or 240 to 255.

IPv4 Addressing

Do Lab 9.2.4

Reserved IP Addresses

Network addressNetwork address – Used to identify the – Used to identify the network itself network itself

All 0s in the host bit positions of the IP All 0s in the host bit positions of the IP address is considered the Network Address.address is considered the Network Address.

Reserved IP Addresses

Broadcast addressBroadcast address – Used for broadcasting – Used for broadcasting packets to all the devices on a networkpackets to all the devices on a network

All binary 1s in the host bit positions of the All binary 1s in the host bit positions of the IP address is considered the Broadcast IP address is considered the Broadcast address for that network.address for that network.

Public and Private IP Addresses A procedure was needed to make sure that addresses A procedure was needed to make sure that addresses

were in fact unique.were in fact unique. Originally, an organization known as the Internet Originally, an organization known as the Internet

Network Information Center (InterNIC) handled this Network Information Center (InterNIC) handled this procedure. procedure.

InterNIC no longer exists and has been succeeded by InterNIC no longer exists and has been succeeded by the Internet Assigned Numbers Authority (IANA). the Internet Assigned Numbers Authority (IANA). IANA carefully manages the remaining supply of IANA carefully manages the remaining supply of

IP addresses to ensure that duplication of publicly IP addresses to ensure that duplication of publicly used addresses does not occur.used addresses does not occur.

Public and Private IP Addresses Public IP addresses are unique. Public IP addresses are unique.

No two machines that connect to a public No two machines that connect to a public network can have the same IP address because network can have the same IP address because public IP addresses are global and standardized.public IP addresses are global and standardized.

All machines connected to the Internet agree to All machines connected to the Internet agree to conform to the system. conform to the system.

Public IP addresses must be obtained from an Public IP addresses must be obtained from an Internet service provider (ISP) or a registry at Internet service provider (ISP) or a registry at some expense.some expense.

Public and Private IP Addresses

With the rapid growth of the Internet, public With the rapid growth of the Internet, public IP addresses were beginning to run out.IP addresses were beginning to run out.

New addressing schemesNew addressing schemes classless interdomain routing (CIDR)classless interdomain routing (CIDR) IPv6 IPv6

CIDR and IPv6 are discussed later in CIDR and IPv6 are discussed later in the course. the course.

Public and Private IP Addresses Private IP addresses are another solution to the Private IP addresses are another solution to the

problem of the impending exhaustion of public IP problem of the impending exhaustion of public IP addresses. addresses.

As mentioned, public networks require hosts to As mentioned, public networks require hosts to have unique IP addresses. have unique IP addresses.

However, private networks that are not connected However, private networks that are not connected to the Internet may use any host addresses, as long to the Internet may use any host addresses, as long as each host within the private network is unique.as each host within the private network is unique.

Public and Private IP Addresses Many private networks exist alongside public Many private networks exist alongside public

networks. networks. However, a private network using just any address However, a private network using just any address

is strongly discouraged because that network might is strongly discouraged because that network might eventually be connected to the Internet.eventually be connected to the Internet.

RFC 1918 sets aside three blocks of IP addresses RFC 1918 sets aside three blocks of IP addresses for private, internal use. for private, internal use.

These three blocks consist of one Class A, a range These three blocks consist of one Class A, a range of Class B addresses, and a range of Class C of Class B addresses, and a range of Class C addresses. addresses.

Public and Private IP Addresses Addresses that fall within these ranges are not routed Addresses that fall within these ranges are not routed

on the Internet backbone. on the Internet backbone. Internet routers immediately discard private addresses. Internet routers immediately discard private addresses. If addressing a nonpublic intranet, a test lab, or a home If addressing a nonpublic intranet, a test lab, or a home

network, these private addresses can be used instead of network, these private addresses can be used instead of globally unique addresses.globally unique addresses.

Private IP addresses can be intermixed with public IP Private IP addresses can be intermixed with public IP addresses. addresses.

This will conserve the number of addresses used for This will conserve the number of addresses used for internal connections. internal connections.

Public and Private IP Addresses Connecting a network using private addresses to Connecting a network using private addresses to

the Internet requires translation of the private the Internet requires translation of the private addresses to public addresses.addresses to public addresses.

This translation process is referred to as Network This translation process is referred to as Network Address Translation (NAT). Address Translation (NAT).

A router usually is the device that performs NAT.A router usually is the device that performs NAT. NAT, along with CIDR and IPv6 are covered in NAT, along with CIDR and IPv6 are covered in

more depth later in the curriculum. more depth later in the curriculum.

Subnetting Subnet addresses include the network portion, plus Subnet addresses include the network portion, plus

a subnet field and a host field. a subnet field and a host field. The subnet field and the host field are created The subnet field and the host field are created

from the original host portion for the entire from the original host portion for the entire network. network.

The ability to decide how to divide the original The ability to decide how to divide the original host portion into the new subnet and host fields host portion into the new subnet and host fields provides addressing flexibility for the network provides addressing flexibility for the network administrator.administrator.

Subnetting To create a subnet address, a network administrator To create a subnet address, a network administrator

borrows bits from the host field and designates them as borrows bits from the host field and designates them as the subnet field.the subnet field.

The minimum number of bits that can be borrowed is two. The minimum number of bits that can be borrowed is two. When creating a subnet, where only one bit was When creating a subnet, where only one bit was

borrowed the network number would be the .0 borrowed the network number would be the .0 network. network.

The broadcast number would then be the .255 network. The broadcast number would then be the .255 network. The maximum number of bits that can be borrowed can The maximum number of bits that can be borrowed can

be any number that leaves at least two bits remaining, for be any number that leaves at least two bits remaining, for the host number.the host number.   

IPv4 vs IPv6 When TCP/IP was adopted in the 1980s, it relied on a When TCP/IP was adopted in the 1980s, it relied on a

two-level addressing scheme. two-level addressing scheme. This offered adequate scalabilityThis offered adequate scalability The designers of TCP/IP could not have predicted The designers of TCP/IP could not have predicted

that their protocol would eventually sustain a global that their protocol would eventually sustain a global network of information, commerce, and network of information, commerce, and entertainment. entertainment.

Over twenty years ago, IP Version 4 (IPv4) offered an Over twenty years ago, IP Version 4 (IPv4) offered an addressing strategy that, although scalable for a time, addressing strategy that, although scalable for a time, resulted in an inefficient allocation of addresses. resulted in an inefficient allocation of addresses.

IPv4 vs IPv6 The Class A and B addresses make up 75 percent The Class A and B addresses make up 75 percent

of the IPv4 address space, however fewer than of the IPv4 address space, however fewer than 17,000 organizations can be assigned a Class A or 17,000 organizations can be assigned a Class A or B network number.B network number.

Class C network addresses are far more numerous Class C network addresses are far more numerous than Class A and Class B addresses, although they than Class A and Class B addresses, although they account for only 12.5 percent of the possible four account for only 12.5 percent of the possible four billion IP addresses. billion IP addresses.

IPv4 vs IPv6 Class C addresses are limited to 254 usable hosts.Class C addresses are limited to 254 usable hosts. This does not meet the needs of larger This does not meet the needs of larger

organizations that cannot acquire a Class A or B organizations that cannot acquire a Class A or B address. address.

Even if there were more Class A, B, and C Even if there were more Class A, B, and C addresses, too many network addresses would addresses, too many network addresses would cause Internet routers to come to a stop under the cause Internet routers to come to a stop under the burden of the enormous size of routing tables burden of the enormous size of routing tables required to store the routes to reach each of the required to store the routes to reach each of the networks. networks.

IPv4 vs IPv6 In 1992, the Internet Engineering Task Force (IETF) In 1992, the Internet Engineering Task Force (IETF)

identified the following two specific concerns: identified the following two specific concerns: Exhaustion of the remaining, unassigned IPv4 network Exhaustion of the remaining, unassigned IPv4 network

addresses. addresses. At the time, the Class B space was on the verge of At the time, the Class B space was on the verge of

depletion. depletion. The rapid and large increase in the size of Internet routing The rapid and large increase in the size of Internet routing

tables occurred as more Class C networks came online. tables occurred as more Class C networks came online. The resulting flood of new network information The resulting flood of new network information

threatened the ability of Internet routers to cope threatened the ability of Internet routers to cope effectively. effectively.

IPv4 vs IPv6

Over the past two decades, numerous Over the past two decades, numerous extensions to IPv4 have been developed.extensions to IPv4 have been developed.

These extensions are specifically designed These extensions are specifically designed to improve the efficiency with which the to improve the efficiency with which the 32-bit address space can be used. 32-bit address space can be used. subnet masks subnet masks classless interdomain routing (CIDR)classless interdomain routing (CIDR)

IPv4 vs IPv6 An even more extendible and scalable version of IP, IP Version 6 An even more extendible and scalable version of IP, IP Version 6

(IPv6), has been defined and developed.(IPv6), has been defined and developed. IPv6 uses 128 bits rather than the 32 bits currently used in IPv4. IPv6 uses 128 bits rather than the 32 bits currently used in IPv4. IPv6 uses hexadecimal numbers to represent the 128 bits. IPv6 uses hexadecimal numbers to represent the 128 bits. IPv6 provides 640 sextrillion addresses. IPv6 provides 640 sextrillion addresses.

IPv6 addresses are 128 bits longIPv6 addresses are 128 bits long Written in hexadecimal formWritten in hexadecimal form Separated by colonsSeparated by colons IPv6 fields are 16 bits longIPv6 fields are 16 bits long To make the addresses easier to read, leading zeros can be To make the addresses easier to read, leading zeros can be

omitted from each field.omitted from each field.

Obtaining an Internet Address A network host needs to obtain a globally A network host needs to obtain a globally

unique address in order to function on the unique address in order to function on the Internet. Internet.

The physical or MAC address that a host The physical or MAC address that a host has is only locally significant, identifying has is only locally significant, identifying the host within the local area network. the host within the local area network.

Since this is a Layer 2 address, the router Since this is a Layer 2 address, the router does not use it to forward outside the LAN.does not use it to forward outside the LAN.

Obtaining an Internet Address

IP addresses are the most commonly used IP addresses are the most commonly used addresses for Internet communications. addresses for Internet communications.

This protocol is a hierarchical addressing This protocol is a hierarchical addressing scheme that allows individual addresses to scheme that allows individual addresses to be associated together and treated as groups.be associated together and treated as groups.

These groups of addresses allow efficient These groups of addresses allow efficient transfer of data across the Internet.transfer of data across the Internet.

Obtaining an Internet Address Network administrators use two methods to assign Network administrators use two methods to assign

IP addresses. IP addresses. static and dynamicstatic and dynamic

Regardless of which addressing scheme is chosen, Regardless of which addressing scheme is chosen, no two interfaces can have the same IP address.no two interfaces can have the same IP address.

Two hosts that have the same IP address could Two hosts that have the same IP address could create a conflict that might cause both of the hosts create a conflict that might cause both of the hosts involved not to operate properly. involved not to operate properly.

Static IP Addresses Static AddressingStatic Addressing

Static assignment works best on small, Static assignment works best on small, infrequently changing networks. infrequently changing networks.

The administrator manually assigns and tracks The administrator manually assigns and tracks IP addresses for each computer, printer, or IP addresses for each computer, printer, or server on the intranet. server on the intranet.

Good recordkeeping is critical to prevent Good recordkeeping is critical to prevent problems which occur with duplicate IP problems which occur with duplicate IP addresses. addresses.

Static IP Addresses Servers should be assigned a static IP address so Servers should be assigned a static IP address so

workstations and other devices will always know workstations and other devices will always know how to access needed services. how to access needed services. Consider how difficult it would be to phone a Consider how difficult it would be to phone a

business that changed its phone number every business that changed its phone number every day. day.

Other devices that should be assigned static IP Other devices that should be assigned static IP addresses are network printers, application addresses are network printers, application servers, and routers. servers, and routers.

Reverse Address Resolution Protocol (RARP) associates a known MAC address with an IP address. associates a known MAC address with an IP address. This association allows network devices to This association allows network devices to

encapsulate data before sending the data out on the encapsulate data before sending the data out on the network. network.

A network device, such as a diskless workstation, A network device, such as a diskless workstation, might know its MAC address but not its IP address. might know its MAC address but not its IP address.

RARP allows the device to make a request to learn its RARP allows the device to make a request to learn its IP address. IP address.

Devices using RARP require that a RARP server be Devices using RARP require that a RARP server be present on the network to answer RARP requests. present on the network to answer RARP requests.

Bootstrap Protocol (BOOTP)

operates in a client-server environment operates in a client-server environment and only requires a single packet and only requires a single packet exchange to obtain IP information.exchange to obtain IP information.

However, unlike RARP, BOOTP However, unlike RARP, BOOTP packets can include the IP address, as packets can include the IP address, as well as the address of a router, the well as the address of a router, the address of a server, and vendor-specific address of a server, and vendor-specific information.information.

Bootstrap Protocol (BOOTP) One problem with BOOTP, however, is that One problem with BOOTP, however, is that

it was not designed to provide dynamic it was not designed to provide dynamic address assignment. address assignment.

With BOOTP, a network administrator With BOOTP, a network administrator creates a configuration file that specifies the creates a configuration file that specifies the parameters for each device.parameters for each device.

The administrator must add hosts and The administrator must add hosts and maintain the BOOTP database. maintain the BOOTP database.

Bootstrap Protocol (BOOTP) Even though the addresses are dynamically Even though the addresses are dynamically

assigned, there is still a one to one relationship assigned, there is still a one to one relationship between the number of IP addresses and the between the number of IP addresses and the number of hosts. This means that for every host on number of hosts. This means that for every host on the network there must be a BOOTP profile with the network there must be a BOOTP profile with an IP address assignment in it. No two profiles can an IP address assignment in it. No two profiles can have the same IP address. Those profiles might be have the same IP address. Those profiles might be used at the same time and that would mean that used at the same time and that would mean that two hosts have the same IP address. two hosts have the same IP address.

Bootstrap Protocol (BOOTP) A device uses BOOTP to obtain an IP address A device uses BOOTP to obtain an IP address

when starting up. when starting up. BOOTP uses UDP to carry messages. BOOTP uses UDP to carry messages. The UDP message is encapsulated in an IP packet.The UDP message is encapsulated in an IP packet. A computer uses BOOTP to send a broadcast IP A computer uses BOOTP to send a broadcast IP

packet using a destination IP address of all 1s, packet using a destination IP address of all 1s, 255.255.255.255 in dotted decimal notation. 255.255.255.255 in dotted decimal notation.

Bootstrap Protocol (BOOTP) A BOOTP server receives the broadcast and then A BOOTP server receives the broadcast and then

sends back a broadcast. sends back a broadcast. The client receives a frame and checks the MAC The client receives a frame and checks the MAC

address. address. If the client finds its own MAC address in the If the client finds its own MAC address in the

destination address field and a broadcast in the IP destination address field and a broadcast in the IP destination field, it takes and stores the IP address destination field, it takes and stores the IP address and other information supplied in the BOOTP and other information supplied in the BOOTP reply message.reply message.

DHCP Dynamic host configuration protocol (DHCP) is Dynamic host configuration protocol (DHCP) is

the successor to BOOTP. the successor to BOOTP. Unlike BOOTP, DHCP allows a host to obtain an Unlike BOOTP, DHCP allows a host to obtain an

IP address dynamically without the network IP address dynamically without the network administrator having to set up an individual profile administrator having to set up an individual profile for each device. for each device. All that is required when using DHCP is a All that is required when using DHCP is a

defined range of IP addresses on a DHCP defined range of IP addresses on a DHCP server. server.

DHCP As hosts come online, they contact the DHCP As hosts come online, they contact the DHCP

server and request an address. server and request an address. The DHCP server chooses an address and leases it The DHCP server chooses an address and leases it

to that host. to that host. With DHCP, the entire network configuration of a With DHCP, the entire network configuration of a

computer can be obtained in one message. computer can be obtained in one message. This includes all of the data supplied by the This includes all of the data supplied by the

BOOTP message, plus a leased IP address and a BOOTP message, plus a leased IP address and a subnet mask. subnet mask.

DHCP The major advantage that DHCP has over BOOTP The major advantage that DHCP has over BOOTP

is that it allows users to be mobile. is that it allows users to be mobile. This mobility allows the users to freely change This mobility allows the users to freely change

network connections from location to location. network connections from location to location. It is no longer required to keep a fixed profile for It is no longer required to keep a fixed profile for

every device attached to the network as was every device attached to the network as was required with the BOOTP system. required with the BOOTP system.

DHCP

The importance to this DHCP advancement The importance to this DHCP advancement is its ability to lease an IP address to a is its ability to lease an IP address to a device and then reclaim that IP address for device and then reclaim that IP address for another user after the first user releases it.another user after the first user releases it.

This means that DHCP offers a one to many This means that DHCP offers a one to many ratio of IP addresses and that an address is ratio of IP addresses and that an address is available to anyone who connects to the available to anyone who connects to the network. network.

Problems in Address Resolution One of the major problems in networking is how to One of the major problems in networking is how to

communicate with other network devices. communicate with other network devices. In TCP/IP communications, a datagram on a local-In TCP/IP communications, a datagram on a local-

area network must contain both a destination MAC area network must contain both a destination MAC address and a destination IP address. address and a destination IP address.

These addresses must be correct and match the These addresses must be correct and match the destination MAC and IP addresses of the host destination MAC and IP addresses of the host device. device. If it does not match, the datagram will be If it does not match, the datagram will be

discarded by the destination host.discarded by the destination host.

Problems in Address Resolution Communications within a LAN segment require Communications within a LAN segment require

two addresses. two addresses. There needs to be a way to automatically map IP to There needs to be a way to automatically map IP to

MAC addresses. MAC addresses. It would be too time consuming for the user to It would be too time consuming for the user to

create the maps manually. create the maps manually. The TCP/IP suite has a protocol, called Address The TCP/IP suite has a protocol, called Address

Resolution Protocol (ARP), which can Resolution Protocol (ARP), which can automatically obtain MAC addresses for local automatically obtain MAC addresses for local transmission. transmission.

Problems in Address Resolution Different issues are raised when data is sent outside Different issues are raised when data is sent outside

of the local area network. of the local area network. Communications between two LAN segments have Communications between two LAN segments have

an additional task. an additional task. Both the IP and MAC addresses are needed for both Both the IP and MAC addresses are needed for both

the destination host and the intermediate routing the destination host and the intermediate routing device. device.

TCP/IP has a variation on ARP called Proxy ARP TCP/IP has a variation on ARP called Proxy ARP that will provide the MAC address of an intermediate that will provide the MAC address of an intermediate device for transmission outside the LAN to another device for transmission outside the LAN to another network segment.network segment.

Address Resolution Protocol With TCP/IP networking, a data packet must With TCP/IP networking, a data packet must

contain both a destination MAC address and a contain both a destination MAC address and a destination IP address. destination IP address.

If the packet is missing either one, the data will not If the packet is missing either one, the data will not pass from Layer 3 to the upper layers. pass from Layer 3 to the upper layers.

In this way, MAC addresses and IP addresses act as In this way, MAC addresses and IP addresses act as checks and balances for each other. checks and balances for each other.

After devices determine the IP addresses of the After devices determine the IP addresses of the destination devices, they can add the destination destination devices, they can add the destination MAC addresses to the data packets. MAC addresses to the data packets.

Address Resolution Protocol Some devices will keep tables that contain MAC Some devices will keep tables that contain MAC

addresses and IP addresses of other devices that are addresses and IP addresses of other devices that are connected to the same LAN. connected to the same LAN.

These are called Address Resolution Protocol These are called Address Resolution Protocol (ARP) tables. (ARP) tables.

ARP tables are stored in RAM memory, where the ARP tables are stored in RAM memory, where the cached information is maintained automatically on cached information is maintained automatically on each of the devices. each of the devices.

It is very unusual for a user to have to make an It is very unusual for a user to have to make an ARP table entry manually. ARP table entry manually.

Address Resolution Protocol Each device on a network maintains its own ARP Each device on a network maintains its own ARP

table. table. When a network device wants to send data across When a network device wants to send data across

the network, it uses information provided by the the network, it uses information provided by the ARP table. ARP table.

When a source determines the IP address for a When a source determines the IP address for a destination, it then consults the ARP table in order destination, it then consults the ARP table in order to locate the MAC address for the destination. to locate the MAC address for the destination.

Address Resolution Protocol

If the source locates an entry in its table, If the source locates an entry in its table, destination IP address to destination MAC destination IP address to destination MAC address, it will associate the IP address to address, it will associate the IP address to the MAC address and then uses it to the MAC address and then uses it to encapsulate the data. encapsulate the data.

The data packet is then sent out over the The data packet is then sent out over the networking media to be picked up by the networking media to be picked up by the destination device. destination device.

Address Resolution Protocol There are two ways that devices can gather MAC There are two ways that devices can gather MAC

addresses that they need to add to the encapsulated data. addresses that they need to add to the encapsulated data. monitor the traffic that occurs on the local network monitor the traffic that occurs on the local network

segment. segment. All stations analyze all traffic to determine if the All stations analyze all traffic to determine if the

data is for them. data is for them. • Part of this process is to record the source IP and Part of this process is to record the source IP and

MAC address of the datagram to an ARP table. MAC address of the datagram to an ARP table. • As data is transmitted, the address pairs populate As data is transmitted, the address pairs populate

the ARP table.the ARP table.

Address Resolution Protocol Another way to get an address pair for data Another way to get an address pair for data

transmission is to broadcast an ARP request.transmission is to broadcast an ARP request. The computer that requires an IP and MAC The computer that requires an IP and MAC

address pair broadcasts an ARP request. address pair broadcasts an ARP request. All the other devices on the local area network All the other devices on the local area network

analyze this request. analyze this request. If one of the local devices matches the IP address If one of the local devices matches the IP address

of the request, it sends back an ARP reply that of the request, it sends back an ARP reply that contains its IP-MAC pair. contains its IP-MAC pair.

Address Resolution Protocol If the IP address is for the local area If the IP address is for the local area

network and the computer does not exist or network and the computer does not exist or is turned off, there is no response to the is turned off, there is no response to the ARP request. ARP request.

In this situation, the source device reports In this situation, the source device reports an error.an error.

If the request is for a different IP network, If the request is for a different IP network, there is another process that can be used.there is another process that can be used.

Proxy ARP Routers do not forward broadcast packets. Routers do not forward broadcast packets. If the feature is turned on, a router performs a proxy If the feature is turned on, a router performs a proxy

ARP. ARP. Proxy ARP is a variation of the ARP protocol. Proxy ARP is a variation of the ARP protocol. In this variation, a router sends an ARP response In this variation, a router sends an ARP response

with the MAC address of the interface on which the with the MAC address of the interface on which the request was received, to the requesting host.request was received, to the requesting host. The router responds with the MAC addresses for The router responds with the MAC addresses for

those requests in which the IP address is not in the those requests in which the IP address is not in the range of addresses of the local subnet. range of addresses of the local subnet.

Default Gateway Another method to send data to the address of a Another method to send data to the address of a

device that is on another network segment is to set device that is on another network segment is to set up a default gateway. up a default gateway.

The default gateway is a host option where the IP The default gateway is a host option where the IP address of the router interface is stored in the address of the router interface is stored in the network configuration of the host. network configuration of the host.

The source host compares the destination IP The source host compares the destination IP address and its own IP address to determine if the address and its own IP address to determine if the two IP addresses are located on the same segment.two IP addresses are located on the same segment.

Default Gateway If the receiving host is not on the same segment, the If the receiving host is not on the same segment, the

source host sends the data using the actual IP address source host sends the data using the actual IP address of the destination and the MAC address of the router. of the destination and the MAC address of the router.

The MAC address for the router was learned from the The MAC address for the router was learned from the ARP table by using the IP address of that router.ARP table by using the IP address of that router.

If the default gateway on the host or the proxy ARP If the default gateway on the host or the proxy ARP feature on the router is not configured, no traffic can feature on the router is not configured, no traffic can leave the local area network. leave the local area network.

One or the other is required to have a connection One or the other is required to have a connection outside of the local area network.outside of the local area network.

Summary Why the Internet was developed and how TCP/IP fits Why the Internet was developed and how TCP/IP fits

the design of the Internet the design of the Internet The four layers of the TCP/IP model The four layers of the TCP/IP model The functions of each layer of the TCP/IP model The functions of each layer of the TCP/IP model The OSI model compared to the TCP/IP model The OSI model compared to the TCP/IP model IP addressing gives each device on the Internet a IP addressing gives each device on the Internet a

unique identifier unique identifier IP address classes are logical divisions of the address IP address classes are logical divisions of the address

space used to meet the needs of various sizes of space used to meet the needs of various sizes of networks networks

Summary Subnetting is used to divide a network into smaller Subnetting is used to divide a network into smaller

networks networks Reserved addresses fulfill a special role in IP Reserved addresses fulfill a special role in IP

addressing and cannot be used for any other addressing and cannot be used for any other purpose purpose

Private addresses cannot be routed on the public Private addresses cannot be routed on the public Internet. Internet.

The function of a subnet mask is to map the parts The function of a subnet mask is to map the parts of an IP address that are the network and the host of an IP address that are the network and the host

Summary Someday IPV4 will be completely obsolete and Someday IPV4 will be completely obsolete and

IPV6 will be the commonly used version IPV6 will be the commonly used version A computer must have an IP address to A computer must have an IP address to

communicate on the Internet communicate on the Internet An IP address may be configured statically or An IP address may be configured statically or

dynamically dynamically A dynamic IP address may be allocated using A dynamic IP address may be allocated using

RARP, BOOTP or DHCP RARP, BOOTP or DHCP

Summary

DHCP supplies more information to a client DHCP supplies more information to a client than BOOTP than BOOTP

DHCP allows computers to be mobile DHCP allows computers to be mobile allowing a connection to many different allowing a connection to many different networks networks

ARP and Proxy ARP can be used to solve ARP and Proxy ARP can be used to solve address resolution problems address resolution problems