CCNA 1 v3.11 Module 9ocw.dongyang.ac.kr/cms_ocw/network/435/note/5_10.pdf · CCNA1 / 1st semester,...
Transcript of CCNA 1 v3.11 Module 9ocw.dongyang.ac.kr/cms_ocw/network/435/note/5_10.pdf · CCNA1 / 1st semester,...
1© 2007, Jae-sul Lee. All rights reserved.
TCP/IP Protocol Suite and IP Addressing
CCNA 1 v3.11 Module 9
22CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Agenda
9.1 Introduction to TCP/IP
9.2 Internet Addresses
9.3 Obtaining an IP address • Networking protocols for Layer 3 or above• Basics of the TCP/IP model• The role of the IP in the TCP/IP network• Concept of the IP address, IP address architecture, subnetting• How an IP address can be assigned to a device• How the MAC address of a device can be known, given the IP
address of that device
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Overview• The Internet is based on the TCP/IP protocol suite
– TCP/IP is ideal for the decentralized and robust Internet – Many common protocols were designed based on the four-layer
TCP/IP model
• TCP/IP and OSI network models – Each model uses its own structure to explain how a network works– Be familiar with both models to understand how a network
functions
• The IP address– A unique identifier for any device on the Internet– Routers use a Layer 3 protocol called the IP protocol to find the
best route to that device
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Overview• Network address space
– Current version of IP (IPv4) has the address space of 232
– IP addresses are classified into class A, B, C, D, and E
– Explosive growth of the Internet has threatened to deplete the supply of IP addresses
– Some solutions includes subnets, network address translation (NAT), and private addresses
– Ultimate solutions is IPv6
• Assigning the IP address to a device– Static assignment
– Dynamic assignment
55CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Module objectives• Students who complete this module should be able to perform the following tasks:
– Explain why the Internet was developed and how TCP/IP fits the design of the Internet
– List the four layers of the TCP/IP model – Describe the functions of each layer of the TCP/IP model – Compare the OSI model and the TCP/IP model– Describe the function and structure of IP addresses– Explain the difference between public and private addressing– Understand the function of reserved IP addresses– Understand why subnetting is necessary – Explain the use of static and dynamic addressing for a device – Understand how dynamic addresses can be assigned with RARP, BootP,
and DHCP– Use ARP to obtain the MAC address to send a packet to another device – Understand the issues related to addressing between networks
66CCNA1 / 1st semester, 2007Network Information & Communication Program,
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9.1 Introduction to TCP/IP
9.2 Internet Addresses
9.3 Obtaining an IP address
• TCP/IP is the 4-layer protocol suit for the Internet• The role of each TCP/IP layer in networking• The comparison between TCP/IP and OSI layers• The growth of the network to the Internet and its operation
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Outlines9.1.1 History and future of TCP/IP
9.1.2 Application layer
9.1.3 Transport layer
9.1.4 Internet layer
9.1.5 Network access layer
9.1.6 The OSI model and the TCP/IP model
9.1.7 Internet architecture
88CCNA1 / 1st semester, 2007Network Information & Communication Program,
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History and future of TCP/IP • The Internet is initiated by the U.S. Department of Defense
(DoD) – Required reliable data transmission to any destination on the
network under any circumstances
– The creation of the TCP/IP model helped to solve this difficult design problem
– The TCP/IP model has since become the standard on which the Internet is based
– The present version of TCP/IP was standardized in Sep. 1981
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Application layer • The role of the application layer
– Handles high-level protocols, representation, encoding, and dialog control in one layer
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Application layer
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Transport layer • The role of the transport layer
– Provides a logical end-to-end connectivity between host applications
• End-to-end means from the source host to the destination host – Does not involve the intermediate route between each end
– The route is selected at the Internet layer
• Provide end-to-end control and reliability– Segmentation of the upper layer (application layer) data into the same
data stream
– Flow control of the data stream
– Error control of the stream
– Reassembly of the data segments
• Uses sliding windows, sequence numbers, and acknowledgments
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Transport layer • Transport layer protocols
– TCP (connection-oriented) & UDP (connectionless)• Segment upper-layer application data
• Send segments from one end device to another
• The functions of TCP– Establish end-to-end operations
– Provide flow control through the use of sliding windows
– Ensure reliability through the use of sequence numbers and acknowledgments
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Transport layer
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Internet layer • The role of the Internet layer
– Select the best path through the network for packets to travel • Best path determination and packet switching occur at this layer
• Internet layer protocols1. Internet Protocol (IP)
• Provides connectionless, best-effort delivery routing of packets. – Looks for the best path to the destination for each packet. – Data integrity is not guaranteed
2. Internet Control Message Protocol (ICMP) • Provides control and messaging capabilities
3. Address Resolution Protocol (ARP) • Determines the MAC address for known IP addresses.
4. Reverse Address Resolution Protocol (RARP) • Assigns an IP address for an NIC with the known MAC address.
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Internet layer
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Internet layer • Operation of the IP
– Defines a packet and an addressing scheme
– Transfers data between the Internet layer and network access layer
– Routes packets to remote hosts
• Characteristics of the IP– Does not guarantee reliability (best-effort)
• No error checking or correction
– Reliability is provided by the upper layers
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Dongyang Technical College
Internet layer
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1818CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Network access layer • The network access layer
– Also called the host-to-network layer– Includes the LAN and WAN technology details (OSI layer 1 & 2)
• Ethernet, token ring, FDDI, ISDN, xDSL, frame relay, ATM, etc.
• Examples of the components of the network access layer– Drivers for software applications, modem cards, NICs, etc. – Modem protocol standards such as SLIP, PPP
• The role of the network access layer – Allows an IP packet to make a physical link to the network media
• Defines the procedures used to interface with the network hardware and access the transmission medium
• Maps IP addresses to physical hardware addresses • Encapsulates IP packets into frames • Defines the physical media connection based on the hardware type
and network interface
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Network access layer
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Network access layer
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The OSI model and the TCP/IP model • Comparison of the OSI model and the TCP/IP model
– Similarities include: • Both have layers. • Both have application layers, though they include very different services. • Both have comparable transport and network layers. • Both models need to be known by networking professionals. • Both assume packets are switched
– Individual packets may take different paths to reach the same destination
– Differences include: • TCP/IP combines the presentation and session layer issues into its application layer. • TCP/IP combines the OSI data link and physical layers into the network access layer. • TCP/IP appears simpler because it has fewer layers. • TCP/IP protocols are the standards around which the Internet developed
– The TCP/IP model gains credibility– Networks are not usually built on the OSI protocol
» The OSI model is used as a guide
• Only TCP provides reliable delivery of packets while Layer 4 of OSI model always does
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The OSI model and the TCP/IP model
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The OSI model and the TCP/IP model
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Internet architecture • The limitation of the LAN
– Geographical distance– Scalability
• Requirements for internetworking– A network of networks– Scalability in size and distance– Flexibility for technology innovations– Adjustability to dynamic conditions on the network – Permit data communications to anyone, anywhere, at any time
• The concept of the Internet (IP network)– Uses the principle of network layer interconnection– Builds the functionality of the network in independent modules
• Allows intermediate networking devices to relay traffic without details about the LAN/WAN technologies and the applications
• Allows a diversity of LAN/WAN technologies at Layers 1 and 2 of the OSI model and a diversity of applications at Layers 5, 6, and 7
2525CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Internet architecture • Internetworking using the router
– Directly connected network
• All networks are directly connected to a router• A router knows about all networks• The router handles any path decisions required for the two networks
to communicate
LAN 1
LAN 2
LAN 3
LAN 4Router
W X
Y Z
2626CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Internet architecture – Internetworking using two or more routers
• Not all networks are directly connected to one another • Option 1
– A router keeps a list of all computers and all the paths to them – Not desirable when the networks grow large
• Option 2– A router keeps a list of all networks (or summary of networks), but
leaves the local delivery details to the local physical networks» Each router shares information about its connected network » The routers pass the information about the networks to other routers
X Y Z
LAN 2LAN 1 LAN 3
Router 1 Router 2
2727CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Internet architecture • User-transparency of the Internet
– The Internet acts like a transparent end-to-end network– The underlying structures can be extremely complex
• Over 90,000 core routes and 300,000,000 end users • Factors that ensures transparency
– All devices in the Internet follow certain hardware, software, and protocol standards
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9.1 Introduction to TCP/IP
9.2 Internet Addresses
9.3 Obtaining an IP address
• Why the IP address is needed in the networking and how it is used• IPv4 address scheme and classification• The use of the reserved IP addresses• Efficient use of IP address space; private IP address, subnetting
2929CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Outlines9.2.1 IP addressing
9.2.2 Decimal and binary conversion
9.2.3 IPv4 addressing
9.2.4 Class A, B, C, D, and E IP addresses
9.2.5 Reserved IP addresses
9.2.6 Public and private IP addresses
9.2.7 Introduction to subnetting
9.2.8 IPv4 versus IPv6
3030CCNA1 / 1st semester, 2007Network Information & Communication Program,
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IP addressing • Concept of IP address
– Each host in a TCP/IP network must have a unique identifier, or IP address
– IP address operates at Layer 3– It allows one computer to locate another computer on a network
• The concept of address grouping– An address is divided into the network address and host address
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3131CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
IP addressing • Why NOT MAC address? Why IP address?
MAC address IP address• Not systematic (Flat)
• Permanently assigned to the hardware
• Works well within a network
• In the switched network, too many ‘flooding of unknown destination’ occur
• Cannot be used to locate a network and a host
• Each switch must know the MAC address of all hosts in the entire network to communicate
• Difficult to use over the Internet
• Systematic (Hierarchical)
• Logically assigned to the networks and the hosts in them
• Can be used to locate a network and a host
• Each router knows the network address of all networks (or the summary of the networks) and the hosts in its own network
3232CCNA1 / 1st semester, 2007Network Information & Communication Program,
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IP addressing
Network A
Network B
A router is a special computer:• Having multiple NIC ports• Multi-homed• Passes traffic between the
ports- It is called ‘routing’
Router
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• Dual-homed computer– IP address is NOT assigned to
the computer, BUT assigned to the interface
– A dual-homed computer is attached to both networks
3333CCNA1 / 1st semester, 2007Network Information & Communication Program,
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IP addressing • Notation of the IP address
– The length is 32-bit, separated by a period every octet– Usually written as four decimal numbers separated by periods
(Dotted decimal numbers)Copyrighted material is cleared
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Decimal and binary conversion • It is important to remember the following relationships
• For more details on the conversion method, see module 1
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IPv4 addressing
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• The structure of the IP address– Consists of two part
• The network address– Identifies the network to which a host belongs
• The host address– Identifies the address of the host in that network
• Use of an IP address – Every packet has source and destination IP address– A router uses the destination IP address in the packet
• Determine the forwarding route from the source network to the destination
– Determine the destination network using the network address– Determine the destination host in that network using the host address
3636CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
IPv4 addressing • Hierarchical structure of the IP address
– First octet of the IP address represents the highest hierarchy• There are 256 groups of IP addresses in this hierarchy• For each group, second octet of the IP address represents the next
highest hierarchy– There are 256 subgroups of IP addresses for a group of IP addresses– …
– Groups in the higher hierarchy represents the network addresses– Subgroups in the lower hierarchy represents the host addresses
3737CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Class A, B, C, D, and E IP addresses • Why class?
– Efficient use of IP address space is possible• Some networks are large, whereas some networks are small• Assign class A network to the large network and assign class
C network to the small network
• IP address classes
0.0.0~255.255.255
0.0~255.255
0~255
8 16 24 32
0 (1~126)
1 0 (128~191)
1 1 0 (192~223)
(240~255)
multicast addressmulticast address
reserved for future usereserved for future use
class A
class B
class C
class D
class E
0.0~255.255
0~255
1 1 1 1
1 1 1 0 (224~239)
3838CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Class A, B, C, D, and E IP addresses • Identifying IP address classes
• Number of networks and hosts in each IP address class
* 0.0.0.0 network and 127.0.0.0 network are reserved for the special uses
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3939CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Class A, B, C, D, and E IP addresses
• IPv4 Address Space
class A
class B
class C
class Dclass E
0
128
192
224
240
(28/2 -2)nets×(224-2)hosts216/4 nets×(216-2)hosts
224/8 nets×(28-2)hosts
4040CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Class A, B, C, D, and E IP addresses
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Reserved IP addresses• Network address
– All 0’s of host address bits• Identifies the network number itself
– Does not specify a specific host– All 0’s of 32 bits
1. Means ‘this host’ whose IP address is unknown to itself2. Means default network
• Broadcast address– All 1’s of host address bits
• Indicates all hosts in that network – All 1’s of 32 bits
• Indicates all hosts in this network when the host does not know its own IP address
• Local loopback address (127.x.x.x, normally 127.0.0.1)– Virtual interface of a device; NOT asigned to the physical interface– Normally used to test the TCP/IP capability of the host itself
4242CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Reserved IP addresses
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Dongyang Technical College
Public and private IP addresses• Allocation of IP addresses
– Managed by IANA– Allocated to the regional Internet registry (RIR)
• Sub-allocated to the national Internet registry (NIR)– Sub-allocated to the ISP
» Users are assigned IP addresses by Internet service providers or Internet Registry
• Public IP address– Obtained from an ISP or a registry – Must be uniquely assigned throughout the Internet– Globally reachable network must use the public IP addresses
• Private IP address– For hosts in the network with no connection to the Internet – Can be non-unique throughout the world
• Should be unique within a network
4444CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Public and private IP addresses• Address allocation for private Internets (RFC 1918)
• Should not be routed outside the corporate LAN• Using private IP addresses with network address translation
– Networks using private IP addresses can be connected to the Internet via NAT
• Internetworking is possible for the hosts that use private IP addresses
– Typically operates at the border of a stub network• The border gateway router performs the NAT process
– Can be one of the solution for the exhaustion of the IP address
(1 Class A network)
(16 Class B networks)
(256 Class C networks)
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4545CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Public and private IP addresses
NATInternal (private or local) network
External (public or global) network
NATprocess
SA 10.0.0.3
DA 128.23.2.2
SA 179.9.8.80
DA 128.23.2.2
NAT Table
SA 128.23.2.2
DA 179.9.8.80
SA 128.23.2.2
DA 10.0.0.3
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Inside local IP address
Inside global IP address
Outside global IP address
10.0.0.3 179.9.8.80 128.23.2.2
4646CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Public and private IP addresses• Using private IP addresses for the point-to-point serial link
– Can be intermixed with public IP addresses– Conserves the number of addresses for internal connections
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4747CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Public and private IP addresses
203.237.160.8
192.168.11.0
192.168.26.0
192.168.7.0
192.168.13.0 192.168.15.0210.181.186.4
203.249.39.111
203.237.166.10
203.249.39.0
203.237.166.0
210.181.186.0
4848CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Introduction to subnetting• Concept of subnetting (RFC 950)
– Dividing a classful network address space into smaller pieces• A class A, B, or C network can be subnetted into several subnets• Subnet mask is used to identify the subnets
– Enables efficient use of IP address spaces– Reduces the size of broadcast domain
• The router is needed to communicate between the subnets• Provides some level of security
131.108.0.0 (Class B) network131.108.1.0 subnetwork
131.108.2.0 subnetwork 131.108.3.0 subnetworkBroadcast domains
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4949CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Introduction to subnetting• Engineering the network with the subnets
– Analyze current network size, future demands– Determine the size of networks and number of subnets
• Subnetting procedures– Borrows most significant bit(s) from the host field bits
• Maximum bits that can be borrowed = the number of host bits - 2– Designate them as the subnet bits– Address bits can be divided into
• Classful network address bits• Subnet address bit(s)• Host bits
8 16 24 32class A
class B
class C
New network address bits
Host address bits
5050CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Introduction to subnetting• Number of useable subnets
– 2subnet bits - 2• All-zeros subnet and all-ones subnet have been excluded
– To avoid confusion with the network’s own address and the broadcast address– Currently, they can be used if not the legacy network (RFC 1878)
• Number of useable hosts in a subnet– 2host bits – 2
• All-zeros host and all-ones host are the address of the subnet itself and the broadcast address, respectively
• Subnet mask– 32-bit – 1’s represent the portion of the network (including the subnet) address– 0’s represent the portion of the host in the subnet– Bitwise logical AND operation with the IP address yields the address of
the subnetwork– Can be represented as the subnet prefix number (number of 1’s)
5151CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Introduction to subnetting
Borrowed bits
Number of subnets (except all-zero subnet and all-one
subnet)Number of hosts per
subnetSubnet mask
(subnet prefix)
Class A Class B Class C Class A Class B Class C Class A Class B Class C
1 21 (21-2) 223-2 215-2 27-2255.128.0.0
(/9)255.255.128.0
(/17)255.255.255.128
(/25)
2 22 (22-2) 222-2 214-2 26-2255.192.0.0
(/10)255.255.192.0
(/18)255.255.255.192
(/26)
3 23 (23-2) 221-2 213-2 25-2255.224.0.0
(/11)255.255.224.0
(/19)255.255.255.224
(/27)
4 24 (24-2) 220-2 212-2 24-2255.240.0.0
(/12)255.255.240.0
(/20)255.255.255.240
(/28)
5 25 (25-2) 219-2 211-2 23-2255.248.0.0
(13)255.255.248.0
(/21)255.255.255.248
(/29)
6 26 (26-2) 218-2 210-2 22-2255.252.0.0
(/14)255.255.252.0
(/22)255.255.255.252
(/30)
7 27 (27-2) - 217-2 29-2 -255.254.0.0
(/15)255.255.254.0
(/23) -
8 28 (28-2) - 216-2 28-2 -255.255.0.0
(16)255.255.255.0
(/24) -
9 29 (29-2) - 215-2 27-2 -255.255.128.0
(/17)255.255.255.128
(/25) -
10 210 (210-2) - 214-2 26-2 -255.255.192.0
(/18)255.255.255.192
(/26) -
11 211 (211-2) - 213-2 25-2 -255.255.224.0
(/19)255.255.255.224
(/27) -
• Quick reference subnetting chart
5252CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Introduction to subnetting• Lab 9.2.7 IP Addressing Basics
• IP-Addressing Exercise
• Subnetting Exercise
Decimal number of last non-zero octet of the subnet mask (number of ones)
Increment of number of subnet
Subnet address increases by
Subnet addresses
128 (1) ×2 128 0, 128192 (2) ×4 64 0, 64, 128, 192224 (3) ×8 32 0, 32, 64, 96, 128, 160, 192, 224240 (4) ×16 16 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, …248 (5) ×32 8 0, 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, …252 (6) ×64 4 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, …254 (7) ×128 2 0, 2, 4, 6, 8, 10, 12, 16, 18, 20, 22, 24, 26, 28, …
5353
Introduction to subnetting• Subnetting chart
/25 /26 /27 /28 /29 /30Class CSubnetTable
.128 (100000000)2 subnets/128 hosts
.192(11000000)
2 subnets/62 hosts
.224(11100000)
6 subnets/30 hosts
.240(11110000)
14 subnets/14 hosts
.248(11111000)
30 subnets/6 hosts
.252(11111100)
62 subnets/2 hosts.0 .0.4 .4 (.5-.6).8 .8 .8 (.9-.10)
.12 (.9-.14) .12 (.13-.14)
.16 .16 .16 .16 (.17-.18)
.20 (.17-.22) .20 (.21-.22)
.24 (.17-.30) .24 .24 (.25-.26)
.28 (.25-.30) .28 (.29-.30)
.32 .32 .32 .32 .32 (.33-.34)
.36 (.33-.38) .36 (.37-.38)
.40 (.33-.46) .40 .40 (.41-.42)
.44 (.33-.62) (.41-.46) .44 (.45-.46)
.48 .48 .48 .48 (.49-.50)
.52 (.49-.54) .52 (.53-.54)
.56 (.49-.60) 0.56 .56 (.57-.58)
.60 (.1~.126) (.57-.62) .60 (.61-.62)
.64 .64 .64 .64 .64 .64 (.65-.66)
.68 (.65-.70) .68 (.69-.70)
.72 (.65-.78) .72 .72 (.73-.74)
.76 (.65-.94) (.73-.78) .76 (.77-.78)
.80 .80 .80 .80 (.81-.82)
.84 (.81-.86) .84 (.85-.86)
.88 (.81-.94) .88 .88 (.89-.90)
.92 (.65-.126) (.89-.94) .92 (.93-.94)
.96 .96 .96 .96 .96 (.97-.98).100 (.97-102) .100 (.101-.102).104 (.97-.110) .104 .104 (.105-.106).108 (.97-.126) (.105-.110) .108(.109-.110).112 .112 .112 .112 (.113-.114).116 (.113-.118) .116 (.117-.118).120 (.113-.126) .120 .120 (.121-.122).124 (.121-.126) .124 (.125-.126).128 .128 .128 .128 .128 .128 .128 (.129-.130).132 (.129-.134) .132 (.133-.134).136 (.129-.142) .136 .136 (.137-.138).140 (.129-.158) (.137-.142) .140 (.1417-.142).144 .144 .144 .144 (.145-.146).148 (.145-.150) .148 (.149-.150).152 (.145-.158) .152 .152 (.153-.154).156 (.129-.190) (.153-.158) .156 (.157-.158).160 .160 .160 .160 .160 (.161-.162).164 (.161-.166) .164 (.165-.166).168 (.161-.174) .168 .168 (.169-.170).172 (.161-.190) (.169-.174) .172 (.173-.174).176 .176 .176 .176 (.177-.178).180 (.177-.182) .180 (.181-.182).184 (.177-.190) .184 .184 (.185-.186).188 (.129~.254) (.185-.190) .188 (.189-.190).192 .192 .192 .192 .192 (.193-.194).196 (.193-.198) .196 (.197-.198).200 (.193-.206) '.200 .200 (.201-.202).204 (.193-.222) (.205-.206) .204 (.205-.206).208 .208 .208 .208 (.209-.210).212 (.209-.214) .212 (.213-.214).216 (.209-.222) .216 .216 (.217-.218).220 (.221-.222) .220 (.221-.222).224 .224 .224 .224 (.225-.226).228 (.225-.230) .228 (.229-.230).232 (.225-.238) .232 .232 (.233-.234).236 (.233-.238) .236 (.237-.238).240 .240 .240 (.241-.242).244 (.241-.246) .244 (.245-.246).248 .248 (.249-.250)
CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
5454CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
IPv4 versus IPv6
(27-2)×(224-2)214×(216-2)
221×(28-2)
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• Allocation of IPv4 address space– Allocated by the class for the organizations
• Class A network for the large organizations• Class B network for the middle-size organizations• Class C network for the small organizations
– Inefficient and insufficient• With the class A, B networks,
too many IP addresses in a network but too few networks
• With the class C networks, toomany networks but too few IPaddresses in a network
– The size of the routing table getstoo large
• Introduced subnetting orCIDR with VLSM
– With the rapidly increasing demand for the IP addresses, they cannot be the perfect solutions
5555CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
IPv4 versus IPv6 • Introduction of new IP addressing scheme
– IPv6 has been developed• Provides enough addresses (2128) for future communication needs
• Structure of the IPv6 address– 128bit (16 octets) address is separated by colon (:) every 16-bit
field – Each field is represented by 4-hexadecimal digits– Leading zeros in each field can be omitted
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5656CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
9.1 Introduction to TCP/IP
9.2 Internet Addresses
9.3 Obtaining an IP address
• How to assign IP information for a host- Statically- Dynamically; RARP, BOTP, DHCP
• How to get the MAC address of the destination host- When the destination is in the same network; ARP- When the destination is outside the same network; ARP, proxy ARP
5757CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Outlines9.3.1 Obtaining an Internet address
9.3.2 Static assignment of an IP address
9.3.3 RARP IP address assignment
9.3.4 BOOTP IP address assignment
9.3.5 DHCP IP address management
9.3.6 Problems in address resolution
9.3.7 Address Resolution Protocol (ARP)
5858CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Obtaining an Internet address
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• Two methods to assign IP addresses1. Static addressing method
2. Dynamic addressing method• BOOTP, RARP, DHCP
5959CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Static assignment of an IP address • Works best on small, infrequently changing networks
– Suitable for network printers, application servers, and routers
• The system administrator manually assigns and tracks– Good recordkeeping is critical to prevent duplicate problems – Possible only when there are a small number of devices to track
• Parameters to be assigned– IP address– Subnet mask– Default gateway– DNS server– Etc.
6060CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
RARP IP address assignment • RARP (Reverse Address Resolution Protocol)
– The client, such as diskless system, knows its own MAC address but not its own IP address
– The server keeps MAC address↔IP address mapping database• The database is maintained statically by the administrator
• Usually, the server is a router
• Associates the client’s MAC address with an IP addresses
– Procedures• The client host initiates a process called a RARP request
– RARP codes are in the ROM of the source device
– RARP requests are broadcast onto the LAN
• RARP server replies with the IP address for the client in the database
• The client binds its own MAC address to the received IP address
6161CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
RARP IP address assignment • General structure of the RARP L2 frame (64 octets)
– Frame header• DA = 0xFFFFFFFFFFFF for RARP request (broadcast)• DA = Client’s MAC address for RARP reply (unicast)• Type = RARP request/reply (0x8035)
• General structure of the RARP packet (28 octets)
DA SA 0x8035 RARP (28Bytes) PAD ( ? Bytes) FCS
0x0001 (Ethernet) 0x0800 (IPv4)0x06 (Ethernet) 0x04 (IPv4) 0x0003/0x0004 (RARP request/reply)
Destination MAC address(Source MAC address for RARP request)
Source MAC addressSource IP addr. (undefined for RARP request)
Source IP address (continued)
Destination IP address (undefined for RARP request)
6262CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
RARP IP address assignment • RARP procedures
0x0001 0x08000x06 0x04 0x0003
FE:ED:F9:23:44:EFundefined
FE:ED:F9:23:44:EFundefined
PAD FCS
FF:FF:FF:FF:FF:FF FE:ED:F9:23:44:EF 0x8035Transmit RARP request frameReceive RARP request frameDeencapsulate the framePass the packet up to the network layer
Packet is NOT for me! RARP request to me!
0x8035
RARP packet for me!
Keep the IP address
192.168.10.36
0x00030x0001 0x0800
0x06 0x04 0x0004FE:ED:F9:65:33:3A
192.168.10.98FE:ED:F9:23:44:EF
192.168.10.36PAD FCS
FE:ED:F9:23:44:EF FE:ED:F9:65:33:3A 0x8035
RARP reply for me!
Unicast RARP reply frameReceive RARP reply frame
192.168.10.36
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6363CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
BOOTP IP address assignment • The bootstrap protocol
– Operates in a client-server environment
– Uses UDP to carry messages
– Only requires a single packet exchange to obtain IP information
– Can get• The IP address, the address of a router, the address of a boot server,
bootfile name, and vendor-specific information – The client uses boot server information and bootfile name for subsequent
boot process
– Subsequent boot process typically uses TFTP for boot and receiving subnet mask, default gateway, DNS server, etc.
– Not designed to provide dynamic address assignment • The administrator must add hosts and maintain the BOOTP database
6464CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
BOOTP IP address assignment • General structure of the BOOTP frame
– Frame header• DA (MAC) = 0xFFFFFFFFFFFF or specified BOOTP server for
request, or client’s MAC address for reply• Type = IPv4 (0x0800)
– IP header• Protocol = UDP• SA (IP) = all 0 (0.0.0.0; means “this host”) for request• DA (IP) = all 1 (255.255.255.255; means “broadcast to this network”)
or specified BOOTP server for request– ‘all 1’ also applies to BOOTP reply because the client still doesn’t know its
own IP address
– UDP header• SP & DP = 67 (for server) & 68 (for client)
DA SA 0x0800 Protocol SA DA FCSSP DP BOOTP (300Bytes)
L4 segment
L3 packet
6565CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
BOOTP IP address assignment • General structure of the BOOTP message
Opcode/message type (Request=1/Reply=2)
H/W address type (Ethernet=1)
H/W address length (6)
Hop count
Transaction ID (randomly selected to identify a session; 4 Bytes)Number of seconds (From the client’s first try) Unused
Client IP Address (filled in by client; all 0s @ request)Your IP Address (filled by the BOOTP server)
Server IP Address (IP address of the server to be used for the subsequent boot process)Gateway IP Address (used in optional cross-gateway booting )
Client H/W Address (16 Bytes)Server Hostname (boot file server; 64 Bytes)
Boot filename (128 Bytes)Vender specific info (64 Bytes)
6666CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
BOOTP IP address assignment • BOOTP request message
1 1 6 0221
2 UnusedClient IP address=0.0.0.0Your IP address=0.0.0.0
Server IP Address=0.0.0.0Gateway IP Address=0.0.0.0
Client H/W Address=FE:ED:F9:23:44:EFServer Hostname (specify boot file server to use; null if unspecified)
Boot filename (specify boot file name to use; null if unspecified)Vender specific info
6767CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
BOOTP IP address assignment • BOOTP reply message
2 1 6 0221
2 UnusedClient IP address=0.0.0.0
Your IP address=192.168.10.36Server IP Address=192.168.10.97 (set to the IP addr. of the server to be used for the
subsequent bootstrap process)Gateway IP Address=0.0.0.0 (set to the IP address of the gateway if the server is not in the
same network; to identify the network to which the client belongs)Client H/W Address=FE:ED:F9:23:44:EF
Server Hostname=TFTP server nameBoot filename = Name of the boot file in the TFTP server
Vender specific info
6868CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
BOOTP IP address assignment
6969CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • Dynamic host configuration protocol (DHCP)
– Successor to BOOTP
– Allows a host to obtain an IP address dynamically• No need to set up an individual profile for each device
• The DHCP server chooses an address from a pre-defined pool of IP addresses and leases it to that host
– Lease period can be pre-defined
• Offers mobility to the clients
• Efficient use of the IP address space is possible
– Only requires a single packet exchange to obtain IP information • Information from BOOTP + subnet mask, DNS server, WINS server,
and other TCP/IP configuration settings
7070CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • Comparison
BOOTP DHCPStatic MAC↔IP mapping from pre-defined table in the server
Dynamic mapping from a pool of IP addresses in the server
Permanent assignment Lease for a pre-defined periodOnly supports 4 basic parameters:
– IP address
– Gateway address
– Subnet mask
– DNS server address
Supports over 30 configuration parameters listed in RFC 1533
RFC 951 in 1985 RFC 2131 in 1997Uses UDP port 67 & 68 (client/server based)
7171CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • Overview of the operation
DiscoverOffer
255.255.255.255
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7272CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • DHCP procedure overview
1. The client locates a DHCP server by broadcasting a DHCPDISCOVER• Sometimes the client may suggest the IP address it wants
2. The server determines whether it can service the request from its own DB • If it cannot, the server may forward the request on to another DHCP server• If it can, the DHCP server unicasts DHCPOFFER packet with lease information
3. The client selects one of the DHCPOFFERs from servers• Usually, the first received DHCPOFFER is selected• The client then broadcasts DHCPREQUEST to inform the selected offer
4. The selected server unicasts DHCPACK to the client• The client receives DHCPACK and begin using the assigned address
immediately • If the server send DHCPNACK, the client restarts the process
5. If the client detects that the address is already in use on the local segment, it will send a DHCPDECLINE message and the process restarts
6. If the client no longer needs the IP address, the client sends a DHCPRELEASE message to the server
7373CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • General structure of the DHCP frame
– Frame header• DA (MAC) = 0xFFFFFFFFFFFF for DHCP discover & request, client’s
MAC address for offer & acknowledge• Type = IPv4 (0x0800)
– IP header• Protocol = UDP• SA (IP) = all 0 (0.0.0.0) for request• DA (IP) = all 1 (255.255.255.255) for DHCP discover & request
– Unselected server must be notified too at the request phase– In many cases, ‘all 1’ also applies to DHCP offer & DHCP acknowledge
because the client still doesn’t know its own IP address» This happens when the client has set flags=0x8000 at the query and request
– UDP header• SP & DP = 67 (for server) & 68 (for client)
DA SA 0x0800 Protocol SA DA FCSSP DP DHCP (548Bytes)
7474CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • General structure of the DHCP message
– Almost the same as that of the BOOTP• Same field length unless specified
Opcode/message type (Request=1/Reply=2)
H/W address type (Ethernet=1)
H/W address length (6)
Hop count
Transaction ID (randomly selected to identify a session)Number of seconds Flags
Client IP Address (filled in by client; all 0s @ discover)Your IP Address (filled by the BOOTP server @ offer)
Server IP AddressGateway IP Address (relay agent; set by the router to gateway address if DHCP server was
outside the client’s network)Client H/W Address
Server Hostname (boot file server)Boot filename
Options (312 Bytes or more)
7575CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • DHCP discover message
1 1 6 012
2 0x8000(broadcast to client)/0x0000(unicast)0.0.0.00.0.0.00.0.0.00.0.0.0
AA:EC:F9:23:44:19NullNull
Options (312 Bytes or more)
7676CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • DHCP offer message
2 1 6 012
2 0x8000(broadcast to client)/0x0000(unicast)0.0.0.0
192.168.10.35192.168.10.98 (or IP address of the next bootstrap server)
0.0.0.0 (set to gateway address if DHCP server was outside the client’s network)AA:EC:F9:23:44:19
NullNull
Server identifier=192.168.10.98
7777CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • DHCP request message
1 1 6 012
2 0x8000(broadcast to client)/0x0000(unicast)0.0.0.00.0.0.00.0.0.00.0.0.0
AA:EC:F9:23:44:19NullNull
Requested IP address=192.168.10.35 Server identifier=192.168.10.98
7878CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management • DHCP acknowledge message
2 1 6 012
2 0x8000(broadcast to client)/0x0000(unicast)0.0.0.0
192.168.10.35192.168.10.98 (or IP address of next bootstrap server)
0.0.0.0 (set to gateway address if DHCP server was outside the client’s network)AA:EC:F9:23:44:19
NullNull
Server identifier=192.168.10.98
7979CCNA1 / 1st semester, 2007Network Information & Communication Program,
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DHCP IP address management
8080CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management• DHCP procedure example
1. Setup in the OS
8181CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
DHCP IP address management
DHCP clients203.249.39.26
2.Network configuration
203.237.160.1 DHCP server
Routers(relay agent)
218.145.241.1
8282CCNA1 / 1st semester, 2007Network Information & Communication Program,
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DHCP IP address management3. DHCP
discover
8383CCNA1 / 1st semester, 2007Network Information & Communication Program,
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DHCP data
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frame
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4. DHCP offer
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DHCP data
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frame
8888CCNA1 / 1st semester, 2007Network Information & Communication Program,
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5. DHCP request
8989CCNA1 / 1st semester, 2007Network Information & Communication Program,
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DHCP data
9090CCNA1 / 1st semester, 2007Network Information & Communication Program,
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frame
9191CCNA1 / 1st semester, 2007Network Information & Communication Program,
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6. DHCP acknowledge
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DHCP data
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frame
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7. Results
9595CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Problems in address resolution • Learning the MAC address↔IP address mapping
– Within a LAN segment• In the Ethernet, source MAC address and source IP address in a frame
is monitored to learn the source host’s MAC address and IP addressby all hosts in the segment
– Monitor broadcast traffic and unicast traffic destined to itself
– It does NOT ALWAYS work
• How do hosts know the MAC address and the IP address of a host that has not sent a packet yet?
– ARP solves this problem
9696CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Problems in address resolution – Across the LAN segments
• MAC address is meaningful only within a LAN– The switch switches a Layer 2 frame transparently based on the
destination MAC address of the frame
– The router switches a Layer 3 packet transparently based on the IP address of the packet
– The router is a special computer with multiple NICs
– Each NIC has its own MAC address for the communication
– To communicate with the host outside a LAN, it is necessary to communicate with the gateway (router) to that network first
– In that case, the MAC address of the NIC in the router is used for the communication
» Proxy ARP or ARP to the default gateway can locate that MAC address
• Learning the MAC address of the destination outside a LAN is meaningless
9797CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Problems in address resolution
9898CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP) • ARP table
– MAC address↔IP address mapping table for other hosts that are connected to the same LAN
• Used to identify the MAC address of the destination, given the IP address of the destination
– Stored in RAM memory – Usually maintained automatically by the OS
9999CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)• Building the ARP table for the hosts within a LAN segment
1. By monitoring the traffic within the segment• Monitor each frame and record its source IP address and MAC
address into the ARP table
• It does not always work
2. By broadcasting the ARP request to the network• ARP request includes the destination IP address whose MAC
address is wanted
• Destination host unicasts ARP reply with its own MAC address
• Receive the ARP reply and build the ARP table from it
100100CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP)• Learning by monitoring at host 176.10.16.1
ARP cache timeout
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101101CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP) • ARP process
102102CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)
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103103CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)• Sending a packet from 176.10.16.1 to 176.10.16.4
– Assume that 176.10.16.1 doesn’t know the MAC address of 176.10.16.4
1 starts ARP request
4 recognizes ARP request4 receives ARP request
4 starts ARP reply1 receives ARP reply1 sends a packet to 44 receives the packet Copyrighted material is cleared
104104CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP)• Example of an ARP for ping
– Pinging from 203.237.160.84 to 203.237.160.81
105105CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP)– Packet flow overview
106106CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)– 203.237.160.84 looks for the MAC address of 203.237.160.81
107107CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP)– 203.237.160.81 replies its MAC address to 203.237.160.81
108108CCNA1 / 1st semester, 2007Network Information & Communication Program,
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– 1st pingrequest
109109CCNA1 / 1st semester, 2007Network Information & Communication Program,
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– 1st pingreply
110110CCNA1 / 1st semester, 2007Network Information & Communication Program,
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– 4th pingrequest
111111CCNA1 / 1st semester, 2007Network Information & Communication Program,
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– 4th pingreply
112112CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)• Data communication in the IP network
1. Anyway, a node has a packet to send• In the router, it may be received from a host or from another router
• In a host, it may be received from the upper layer of the host
• It has a source IP address– It is the sending end’s IP address
• It has a destination IP address– It is the receiving end’s IP address
2. A node has its own IP address and the subnet mask• Represents the network address it belongs + node address in the
network
113113CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)3. Determine the best path toward the destination (routing at L3)
• Determine the destination network– The IP address of the node (source) and destination are logical ANDed
with the subnet mask, respectively
– If the two results are the same, the destination network is the same as the network to which the node belongs
– If they are different, the destination network is not the same• Determine the best output port to the destination network
– A routing table is used to determine the best path» The routing table has a list of networks and the cost of each port through
which a packet travels to the destination network» Select the port that has the minimum cost to the destination network
– If the destination network is directly connected to the node, the selected port is directly connected to that network
– If not, the selected port is connected to the gateway to the destination network
» Normally, the gateway is a router’s port
114114CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)4. Prepare a frame to send to the selected output port (Framing at
L2)• Now, the packet is to be encapsulated into a frame
– The source and the destination MAC address are needed• The source MAC address is that of the output port (NIC)• There are two cases for the destination MAC address
– If the destination network is directly connected to the output port,» The destination MAC address is that of the destination device’s NIC» It can be determined by the normal ARP broadcast to that network» The frame is sent directly to the destination
– If not, the frame must be routed by the gateway» The host send the packet to the default gateway to have it routed» The destination MAC address is that of the receiving port of the gateway» It can be determined by one of the following methods
115115CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Address Resolution Protocol (ARP)• ARP for communication with outside the LAN segment
– The node must communicate with the router (gateway) first– Determining the MAC address of the gateway
1. If the IP address of the default gateway is set in the node, broadcast ARP request for the IP address of the default gateway
2. If the IP address of the default gateway is NOT set, broadcast ARP request for IP address of the destination host
– Some legacy systems do not have the means to set the default gateway
– If the gateway (router) is set to work as a proxy ARP (default for the Cisco router), it replies the ARP broadcast with the MAC address of its own incoming port
• Both of the results are the same
– The source node uses the MAC address of the default gateway as the destination MAC address
• Destination IP address is unchanged
116116CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Router Router
Address Resolution Protocol (ARP)
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• Proxy ARP
• Default gateway
117117CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP)
What do these results mean?
118118CCNA1 / 1st semester, 2007Network Information & Communication Program,
Dongyang Technical College
Address Resolution Protocol (ARP) • Lab 9.3.7 Workstation ARP
1. Find the IP address of the host in the same network2. Prepare Ethereal or Protocol Inspector for capturing ARP packet
– Apply capture filter for the ARP packet
3. Display current MAC address table by typing arp –a in the command window4. Clear MAC address table by typing arp –d in the command window and
display the MAC address table again5. Start capture at the Ethereal or Protocol Inspector 6. Ping to the host in the same network7. Ping to the host outside the network (such as www.yahoo.com) 8. Stop capture at the Ethereal or Protocol Inspector 9. Display the ARP table10.Analyze the sender, receiver, replier, and the contents of ARP packets for both
case (steps 6 & 7) and explain the results– Caution: In the college network, ping to the outside the campus network is
impossible because of the FIREWALL
119119CCNA1 / 1st semester, 2007Network Information & Communication Program,
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Summary• Students should understand the following main points:
– Why the Internet was developed and how TCP/IP fits the design of the Internet– The four layers of the TCP/IP model– The functions of each layer of the TCP/IP model– The OSI model compared to the TCP/IP model– IP addressing gives each device on the Internet a unique identifier– IP address classes are logical divisions of the address space used to meet the needs of
various size networks– Subnetting is used to divide a network into smaller networks– Reserved addresses fulfill a special role in IP addressing and cannot be used for any other
purpose– Private addresses cannot be routed on the public Internet– The function of a subnet mask is to map the parts of an IP address that are the network and
the host– Someday IPV4 will be completely obsolete and IPV6 will be the commonly used version– A computer must have an IP address to communicate on the Internet– An IP address may be configured statically or dynamically– A dynamic IP address may be allocated using RARP, BOOTP, or DHCP– DHCP supplies more information to a client than BOOTP– DHCP allows computers to be mobile allowing a connection to many different networks– ARP and Proxy ARP can be used to solve address resolution problems