TCPIP

© 2000, Cisco Systems, Inc. 8-1

Chapter 8

Interconnecting Networks with

TCP/IP

© 2000, Cisco Systems, Inc. www.cisco.com ICND v1.0a—8-3

Upon completion of this chapter you will be able to perform the following tasks:• Identify the IP protocol stack, its protocol layer functions, and commonly used IP protocols• Identify IP address classes, IP addresses, IP subnet masks, IP network numbers, subnet numbers, and possible host numbers.• Configure IP addresses and subnet masks on a router interface and optionally configure a host table.• Interconnect the VLANs with a layer three device such as a router on a stick.

Objectives


Early protocol suiteUniversal

Introduction to TCP/IPHost

Internet

TCP/IP

Host


TCP/IP Protocol Stack

7

6

5

4

3

2

5

4

3

2

Application

Presentation

Session

Transport

Network

Data Link

Physical1

Application

Transport

Internet

Data Link

Physical1


Application Layer Overview

*Used by the router

Application

Transport

Internet

Data Link

Physical

File Transfer- TFTP *- FTP *- NFS

E-Mail- SMTP

Remote Login- Telnet *- rlogin *

Network Management- SNMP *

Name Management- DNS*


Transport Layer Overview

Transmission ControlProtocol (TCP)

User Datagram Protocol (UDP)

Application

Transport

Internet

Data Link

Physical

Connection-Oriented

Connectionless


TCP Segment Format

Source port (16) Destination port (16)

Sequence number (32)

Headerlength (4)

Acknowledgement number (32)

Reserved (6) Code bits (6) Window (16)

Checksum (16) Urgent (16)

Options (0 or 32 if any)

Data (varies)

20Bytes

Bit 0 Bit 15 Bit 16 Bit 31


Port Numbers

TCP

Port Numbers

FTP

TransportLayer

TELNET

DNS

SNMP

TFTP

SMTP

UDP

ApplicationLayer

21 23 25 53 69 161

RIP

520


TCP Port Numbers

SourcePort

Dest.Port …

Host A

1028 23 …SP DP

Host ZTelnet Z

Dest. port = 23.Send packet to my

Telnet application.


Send SYN (seq=100 ctl=SYN)

SYN received

Host A Host B

TCP Three Way Handshake/Open Connection

1



SYN received

Send SYN, ACK (seq=300 ack=101 ctl=syn,ack)

Host A Host B

SYN received

1

2




SYN received

Send SYN, ACK (seq=300 ack=101 ctl=syn,ack)

Established(seq=101 ack=301 ctl=ack)

Host A Host B

1

2

3

SYN received



TCP Simple Acknowledgment

Window size = 1

Sender Receiver



Window size = 1

Sender Receiver

Send 1 Receive 1



Window size = 1

Sender Receiver

Send 1 Receive 1

Receive ACK 2 Send ACK 2



Window size = 1

Sender Receiver

Send 1 Receive 1


Send 2Receive 2



Window size = 1

Sender Receiver

Send 1 Receive 1


Send 2Receive 2

Receive ACK 3Send ACK 3



Window size = 1

Sender Receiver

Send 1 Receive 1


Send 2Receive 2


Send 3Receive 3


TCP Sequence and Acknowledgment Numbers

SourcePort

Dest.Port

…Sequence#

Acknowledgement#

Source Dest. Seq. Ack.1028 23 10 1

I justsent #10.



I just got #10,now I need #11.

SourcePort

Dest.Port …Sequence

#Acknowledgement

#

1028 23

Source Dest.

1010

Seq.

1

Ack.

102823

Source Dest.

1111

Seq.

1

Ack.

I justsent #10.



SourcePort


#Acknowledgement

#

1028 23

Source Dest.

1111

Seq.

2

Ack.

1028 23

Source Dest.

1010

Seq.

1

Ack.

102823

Source Dest.

1111

Seq.

1

Ack.


I justsent #11.



SourcePort


#Acknowledgement

#

1028 23

Source Dest.

1111

Seq.

101

Ack.

1028 23

Source Dest.

1010

Seq.

100

Ack.

102823

Source Dest.

1111

Seq.

100

Ack.

102823

Source Dest.

1212

Seq.

101

Ack.


I justsent #11.


TCP Windowing

Sender Receiver


TCP Windowing

Window size = 3Send 2

Sender ReceiverWindow size = 3Send 1




TCP Windowing

Sender Window size = 3Send 1


ACK 3Window size = 2

Packet 3 isDropped

Receiver



TCP Windowing




Packet 3 isDropped



Receiver



TCP Windowing




Packet 3 isDropped




ReceiverWindow size = 3


No sequence or acknowledgment fields

UDP Segment Format

Source port (16) Destination port (16)

Length (16)

Data (if any)

1Bit 0 Bit 15 Bit 16 Bit 31

Checksum (16)

8Bytes


Internet Layer Overview

OSI network layer corresponds to the TCP/IP internet layer

Internet Protocol (IP)

Internet Control MessageProtocol (ICMP)

Address ResolutionProtocol (ARP)

Reverse AddressResolution Protocol (RARP)

Application

Transport

Internet

Data Link

Physical


IP Datagram

Version(4)

Destination IP Address (32)

Options (0 or 32 if any)

Data (varies if any)

1Bit 0 Bit 15 Bit 16 Bit 31Header

Length (4)Priority & Type of Service (8) Total Length (16)

Identification (16)Flags

(3) Fragment offset (13)

Time to live (8) Protocol (8) Header checksum (16)

Source IP Address (32)

20Bytes


Determines destination upper-layer protocol

Protocol Field

TransportLayer

InternetLayer

TCP UDP

ProtocolNumbers

IP

176


Internet Control Message Protocol

Application

Transport

Internet

Data Link

Physical

Destination Unreachable

Echo (Ping)

Other

ICMP1


Address Resolution Protocol

172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???

I need the Ethernet address of 176.16.3.2.



172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???

I heard that broadcast. The message is for me. Here is my Ethernet address.




172.16.3.1

IP: 172.16.3.2 Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???





Map IP MAC Local ARP

172.16.3.1

IP: 172.16.3.2 Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???




Reverse ARP

Ethernet: 0800.0020.1111 IP = ???

What is my IP address?


Reverse ARP

Ethernet: 0800.0020.1111 IP = ???


I heard that broadcast. Your IP address is 172.16.3.25.


Reverse ARP

Ethernet: 0800.0020.1111IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???




Reverse ARP

Map MAC IP

Ethernet: 0800.0020.1111IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???




• Unique addressing allows communication between end stations

• Path choice is based on destination addressLocation is represented by an address

Introduction to TCP/IP Addresses

172.18.0.2

172.18.0.1

172.17.0.2172.17.0.1

172.16.0.2

172.16.0.1

SADAHDR DATA10.13.0.0 192.168.1.0

10.13.0.1 192.168.1.1


IP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

32 bits


IP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

128 64 32 16 8 4 2 1

11111111 11111111 11111111 11111111Binary

32 bits

1 8 9 16 17 24 25 32

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1


IP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

128 64 32 16 8 4 2 1

11111111 11111111 11111111 11111111

10101100 00010000 01111010 11001100

Binary

32 bits

172 16 122 204ExampleDecimalExampleBinary

1 8 9 16 17 24 25 32

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1


Class A:

Class B:

Class C:

Class D: Multicast

Class E: Research

IP Address Classes

Network Host Host Host

Network Network Host Host

Network Network Network Host

8 bits 8 bits 8 bits 8 bits


IP Address Classes

1

Class A:Bits:

0NNNNNNN Host Host Host8 9 16 17 24 25 32

Range (1-126)1

Class B:Bits:

10NNNNNN Network Host Host8 9 16 17 24 25 32

Range (128-191)1

Class C:Bits:

110NNNNN Network Network Host

8 9 16 17 24 25 32

Range (192-223)1

Class D:Bits:

1110MMMM Multicast Group Multicast Group Multicast Group

8 9 16 17 2425 32

Range (224-239)


Host Addresses

172.16.2.2

172.16.3.10

172.16.12.12

10.1.1.1

10.250.8.11

10.180.30.118

E1

172.16 12 12Network Host

. . Network Interface

172.16.0.0

10.0.0.0

E0

E1

Routing Table

172.16.2.1

10.6.24.2

E0


11111111

Determining Available Host Addresses

172 16 0 0

10101100 00010000 00000000 00000000

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Network Host

00000000 00000001

11111111 11111111 11111111 11111110

......

00000000 00000011 11111101

123

655346553565536-

...

265534

N

2N-2 = 216-2 = 65534


IP Address Classes Exercise

Address Class Network Host

10.2.1.1

128.63.2.100

201.222.5.64

192.6.141.2

130.113.64.16

256.241.201.10


IP Address Classes Exercise Answers

Address Class Network Host

10.2.1.1

128.63.2.100

201.222.5.64

192.6.141.2

130.113.64.16

256.241.201.10

A

B

C

C

B

Nonexistent

10.0.0.0

128.63.0.0

201.222.5.0

192.6.141.0

130.113.0.0

0.2.1.1

0.0.2.100

0.0.0.64

0.0.0.2

0.0.64.16


Network 172.16.0.0

172.16.0.0

Addressing without Subnets

172.16.0.1 172.16.0.2 172.16.0.3

…...

172.16.255.253 172.16.255.254


Network 172.16.0.0

Addressing with Subnets

172.16.1.0 172.16.2.0

172.16.3.0

172.16.4.0


Subnet Addressing

172.16.2.200

172.16.2.2

172.16.2.160

172.16.2.1

172.16.3.5

172.16.3.100

172.16.3.150

E0

172.16Network

Network Interface

172.16.0.0

172.16.0.0

E0

E1

New Routing Table 2 160Host

. .

172.16.3.1E1


Subnet Addressing

172.16.2.200

172.16.2.2

172.16.2.160

172.16.2.1

172.16.3.5

172.16.3.100

172.16.3.150

172.16.3.1

E0E1

172.16 2 160Network Host

. . Network Interface

172.16.2.0

172.16.3.0

E0

E1

New Routing Table

Subnet


Subnet Mask

172 16 0 0

255 255 0 0

255 255 255 0

IPAddress

DefaultSubnet

Mask

8-bitSubnet

Mask

Network Host

Network Host

Network Subnet Host

Also written as “/16” where 16 represents the number of 1s in the mask.

Also written as “/24” where 24 represents the number of 1s in the mask.

11111111 11111111 00000000 00000000


Decimal Equivalents of Bit Patterns

0 0 0 0 0 0 0 0 = 0

1 0 0 0 0 0 0 0 = 128

1 1 0 0 0 0 0 0 = 192

1 1 1 0 0 0 0 0 = 224

1 1 1 1 0 0 0 0 = 240

1 1 1 1 1 0 0 0 = 248

1 1 1 1 1 1 0 0 = 252

1 1 1 1 1 1 1 0 = 254

1 1 1 1 1 1 1 1 = 255

128 64 32 16 8 4 2 1


16

Network Host

172 0 0

10101100

11111111

10101100

00010000

11111111

00010000

00000000

00000000

10100000

00000000

00000000

Subnets not in use—the default

00000010

Subnet Mask without Subnets

172.16.2.160

255.255.0.0

NetworkNumber


Network number extended by eight bits

Subnet Mask with Subnets

16

Network Host

172.16.2.160

255.255.255.0

172 2 0

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

00000000

00000000

00000010

Subnet

NetworkNumber

128

192

224

240

248

252

254

255


Subnet Mask with Subnets (cont.)

Network Host

172.16.2.160

255.255.255.192

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

Subnet

Network number extended by ten bits

16172 2 128NetworkNumber

128

192

224

240

248

252

254

255

128

192

224

240

248

252

254

255


Subnet Mask Exercise

Address Subnet Mask Class Subnet

172.16.2.10

10.6.24.20

10.30.36.12

255.255.255.0

255.255.240.0

255.255.255.0


Subnet Mask Exercise Answers

Address Subnet Mask Class Subnet

172.16.2.10

10.6.24.20

10.30.36.12

255.255.255.0

255.255.240.0

255.255.255.0

B

A

A

172.16.2.0

10.6.16.0

10.30.36.0


Broadcast Addresses

172.16.1.0172.16.2.0

172.16.3.0

172.16.4.0

172.16.3.255(Directed broadcast)

255.255.255.255(Local network broadcast) XX

172.16.255.255(All subnets broadcast)


Addressing Summary Example

16172 2 160

10101100 00010000 1010000000000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

4

1



10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

16172 2 160



10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

7

16172 2 160



10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

16172 2 160



10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

16172 2 160



10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

16172 2 160



10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

7

16172 2 160



10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

7

8

16172 2 160



10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

172.16.2.128

172.16.2.191

172.16.2.129

172.16.2.190

1

2

3

4

56

7

89

16172 2 160


IP Host Address: 172.16.2.121Subnet Mask: 255.255.255.0

Subnet Address = 172.16.2.0Host Addresses = 172.16.2.1–172.16.2.254Broadcast Address = 172.16.2.255Eight bits of subnetting

Network Subnet Host

10101100 00010000 00000010 11111111

172.16.2.121:255.255.255.0:

1010110011111111

Subnet: 10101100 00010000

0001000011111111

00000010

00000010

1111111101111001 00000000

00000000

Class B Subnet Example

Broadcast:

Network


Subnet Planning

Other subnets

192.168.5.16

192.168.5.32 192.168.5.48

20 subnets5 hosts per subnetClass C address: 192.168.5.0


11111000

IP Host Address: 192.168.5.121Subnet Mask: 255.255.255.248

Network Subnet Host

192.168.5.121: 1100000011111111

Subnet: 11000000 10101000

1010100011111111

00000101

00000101

1111111101111001

01111000

255.255.255.248:

Class C Subnet Planning Example

Subnet Address = 192.168.5.120Host Addresses = 192.168.5.121–192.168.5.126Broadcast Address = 192.168.5.127Five Bits of Subnetting

Broadcast:

NetworkNetwork

11000000 10101000 00000101 01111111


Broadcast Addresses Exercise

Address Class Subnet Broadcast

201.222.10.60 255.255.255.248

Subnet Mask

15.16.193.6 255.255.248.0

128.16.32.13 255.255.255.252

153.50.6.27 255.255.255.128


Broadcast Addresses Exercise Answers

153.50.6.127

Address Class Subnet Broadcast

201.222.10.60 255.255.255.248 C 201.222.10.63201.222.10.56

Subnet Mask

15.16.193.6 255.255.248.0 A 15.16.199.25515.16.192.0

128.16.32.13 255.255.255.252 B 128.16.32.15128.16.32.12

153.50.6.27 255.255.255.128 B 153.50.6.0


Switch IP Address Configuration

• Assigns an address and subnet mask• Starts IP processing on a switch

Switch(config)#ip address ip-address subnet-mask

Switch(config)#ip default-gateway ip-address

• Specifies a default gateway


Router IP Address Configuration

• Assigns an address and subnet mask• Starts IP processing on a router interface

Router(config-if)#ip address ip-address subnet-mask


Router IP Address Configuration

Router(config-line)#ip netmask-format {bitcount | decimal | hexadecimal}

• Sets format of network mask for a specific line

Router#term ip netmask-format {bitcount| decimal | hexadecimal}

• Sets display format of network mask forcurrent session


• Defines static host name to IP address mapping

• Hosts/interfaces selectable by name or IP address

Router IP Host Names

Router(config)#ip host name [tcp-port-number]address [address]

ip host Norine 172.16.3.1 192.168.3.1ip host Roger 172.16.4.3


• Specifies one or more hosts that supplyhost name to logical address resolution

Router Name Server Configuration

Router(config)#ip name-server server-address1 [[server-address2]...[server-address6]]

DNS Server


• DNS enabled by default

Router Name System

Router(config)#ip domain-lookupRouter(config)#endRouter#patTranslating ”pat"...domain server (255.255.255.255)% Unknown command or computer name, or unable to find computer addressRouter#config tRouter(config)#no ip domain-lookupRouter(config)#endRouter#patTranslating ”pat"% Unknown command or computer name, or unable to find computer addressRouter#


Router Display Host Names

Router#show hostsDefault domain is not setName/address lookup uses domain serviceName servers are 255.255.255.255

Host Flags Age Type Address(es)Norine (perm, OK) 0 IP 172.16.100.100Roger (perm, OK) 0 IP 172.16.100.101Frank (perm, OK) 0 IP 172.16.200.200Bob (perm, OK) 0 IP 172.16.200.201

• Shows the host table


VLAN to VLAN Overview

VLAN 1 VLAN 2

ISL

10.1.1.2 10.2.2.2

Network layer devices combine multiple broadcast domains

Router on a stick

Application

TCPIP

ISLEthernet

Fa0/0


Dividing a Physical Interface into Subinterfaces

FastEthernet 0/0

FastEthernet 0/0.2FastEthernet 0/0.3

FastEthernet 0/0.1

Physical interfaces can be divided into multiple subinterfaces


ISL Encapsulation

• Enables ISL on a subinterface

Router(config-subif)#encapsulation isl vlan identifier


Routing Between VLANs

VLAN 1 VLAN 2

ISL

interface fastethernet 0/0 no ip address!interface fastethernet 0/0.1 ip address 10.1.1.1 255.255.255.0 encapsulation isl 1interface fastethernet 0/0.2 ip address 10.2.2.1 255.255.255.0 encapsulation isl 2

FastE0/0

10.1.1.2 10.2.2.2


Routing Between WANs

ISL

interface Serial0 ip address 172.16.1.1 255.255.255.0

Application

TCPIP

HDLCSerial

S0

172.16.1.1172.16.1.2

VLAN 1 VLAN 2

10.1.1.2 10.2.2.2


Visual Objective

core_ server

wg_sw_a10.1.1.10

wg_sw_l10.1.1.120

...

e0/1fa0/26(port A)

e0/1fa0/26(port A)

fa0/1 fa0/12fa0/24

core_sw_a10.1.1.2

core_sw_b10.1.1.4

fa0/12 fa0/1fa0/13 fa0/13

fa0/27(port B)

fa0/27(port B)

wg_pc_a10.2.2.12

wg_pc_l10.13.13.12

Core_ro

fa0/23

fa0/0

fa0/14fa0/14

VLAN2

VLAN13

SUBNET VLAN POD10.1.1.0 1 wg_ro_x, wg_sw_x, core_sw_a, core_sw_b10.2.2.0 2 wg_pc_a, core_server, core_ro10.3.3.0 3 wg_pc_b, core_server, core_ro10.4.4.0 4 wg_pc_c, core_server, core_ro10.5.5.0 5 wg_pc_d, core_server, core_ro10.6.6.0 6 wg_pc_e, core_server, core_ro10.7.7.0 7 wg_pc_f, core_server, core_ro10.8.8.0 8 wg_pc_g, core_server, core_ro10.9.9.0 9 wg_pc_h, core_server, core_ro10.10.10.0 10 wg_pc_i, core_server, core_ro10.11.11.0 11 wg_pc_j, core_server, core_ro10.12.12.0 12 wg_pc_k, core_server, core_ro10.13.13.0 13 wg_pc_l, core_server, core_ro

SUBNET VLAN POD10.1.1.0 1 wg_ro_x, wg_sw_x, core_sw_a, core_sw_b10.2.2.0 2 wg_pc_a, core_server, core_ro10.3.3.0 3 wg_pc_b, core_server, core_ro10.4.4.0 4 wg_pc_c, core_server, core_ro10.5.5.0 5 wg_pc_d, core_server, core_ro10.6.6.0 6 wg_pc_e, core_server, core_ro10.7.7.0 7 wg_pc_f, core_server, core_ro10.8.8.0 8 wg_pc_g, core_server, core_ro10.9.9.0 9 wg_pc_h, core_server, core_ro10.10.10.0 10 wg_pc_i, core_server, core_ro10.11.11.0 11 wg_pc_j, core_server, core_ro10.12.12.0 12 wg_pc_k, core_server, core_ro10.13.13.0 13 wg_pc_l, core_server, core_ro


Summary

After completing this chapter, you should be able to perform the following tasks:• Identify the TCP/IP protocol stack and the functions of

each layer• Separate an IP address into its subcomponents: the

network, subnet, and host portions• Configure IP addresses on Cisco router and switch

interfaces• Interconnect VLANs using a layer three device such

as a “router on a stick”


Review Questions

1. What is the difference between the TCP and UDP transport layer protocols?

2. Given a host with IP address, 192.168.20.1 255.255.255.240, how many other hosts can you have in that network?

3. What is required to interconnect separate VLANs?

TCPIP

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