CCENT - · PDF fileCCENT Course Outline Chapter 3: The Cisco Router and Switch Interface - Cisco IOS - Cisco CLI - Administrative Functions - Configuring Interfaces

© Copyright 2008 Course Outsource. All Rights Reserved.1

© Copyright 2008 Course Outsource. All Rights Reserved.

CCENT

Cisco Certified Entry Networking Technician

CCIP, CCIE, CCDA, CCDP, CCENT, CCNP, CCNA, CCVO, VLANDirector, TrafficDirector, CiscoWorks 2000, ONS 15454 Secure PIX Firewall, Secure Virtual Private Networks, Cisco, Cisco Systems, Cisco Systems Logo, Catalyst, EtherChannel, IOS and LightStream are registered trademarks of Cisco Systems, Inc. or its affiliates in the US and certain other countries.

© Copyright 2008 Course Outsource. All Rights Reserved. 2


IntroductionIntroduction

This is a 5 day hands-on course which covers the following exam objectives.

ICND1 (640-822)

Other CCNA exams:ICND2 (640-816)CCNA (640-802)



Cisco offers several options as a stepping stone approach to CCIE certification:

CCNP: Routing/SwitchingCCSP: SecurityCCVP: Voice/TelephonyCCIE: R/S, Security, Voice, Storage,

Service Provider

Cisco Professional Certifications

Service provider and Storage networking CCIE also exist, but do not have lower level certifications



CCENT (ICND1) 1.0 ExamCCENT (ICND1) 1.0 Exam

• Around 56 items• Around 804 out of 1000 to pass• The amount of questions and percent to pass

could vary on each exam• About 90 minutes• Cannot return to questions• Simulation, Test-let, Sim-let, multiple choice,

fill-in-the-blank, and drag n’ drop questions



CCENT Course OutlineCCENT Course Outline

Chapter 1: Internetworking

- History of Networking- Define Internetworking- Internetworking terms- Internetworking devices- Security Threats- OSI Reference Model- Ethernet Networking

Chapter 2: Introduction to TCP/IP- TCP/IP Protocol Stack

* TCP, UDP, IP, ICMP, ARP, RARP, Proxy ARP- IP addressing- Class C Subnetting




Chapter 3: The Cisco Router and Switch Interface- Cisco IOS- Cisco CLI- Administrative Functions- Configuring Interfaces- Introduction to Cisco Catalyst Switches

Chapter 4: Managing a Cisco Internetwork- Copying and saving the IOS and configuration- Dynamic Host Configuration Protocol- Domain Name System- Troubleshooting Cisco networks




Chapter 5: IP Routing - Basic IP routing- Static Routing- RIPv1 and RIPv2

Chapter 6: VLSM and Summarization- VLSM design and implementation

- Discontiguous Networks

- Summarization




Chapter 7: Network Address Translation- Static NAT

- Dynamic NAT Pools

- Port Address Translation (PAT)

Chapter 8: VLANs and STP- Virtual LANs (VLANs)

- Spanning Tree Protocol (STP)




Chapter 9: Wireless LANs- 802.11

- Basic Service Sets (BSS)

Chapter 10: Cisco WAN Support

- Basic WAN

- HDLC

- PPP

- Frame Relay

Chapter 11: Secure Device Manager

- Overview



PrefacePreface

Course Conventions


© Copyright 2006 Course Outsource. All Rights Reserved. © Copyright 2008 Course Outsource. All Rights Reserved.

LocalLocal--Area and WideArea and Wide--Area Area Network Symbols KeyNetwork Symbols Key

Router Bridge Ethernet SwitchATM Switch

Hub MAUConcentrator Server

Comm Server CSU/DSUWAN Cloud

Serial LinesEthernet

Modem



Syntax ConventionsSyntax Conventions

Router prompts are in BLACK as follows:

R1#

Router commands to be entered by the user are in GREEN as follows:

R1(config)# interface serial 0R1(config-if)# shutdown



InternetworkingInternetworking

Chapter 1

Welcome to the exciting world of internetworking. This first chapter will really help you understand the basics of internetworking by focusing on how to connect networks together using Cisco routers and switches. To get all that down, you’ll first need to know exactly what an internetwork is, right? You create an internetwork when you take two or more LANs or WANs and connect them via a router, and configure a logical network addressing scheme with a protocol like IP.



Network EvolutionNetwork Evolution

• 1960s and 1970s - United States Department of Defense

(DOD) performed research. The Defense Advanced Research

Project Agency (DARPA) was the group performing the

research. The outcome was ARPANET which later became the

Internet. Mainly centered around a mainframe with

unintelligent terminals communicating with the host.

• 1970s and 1980s - Introduction of PCs. Local-area-

networks (LANs) grew primarily to decrease costs. DEC VAX

systems and DECnet were common. Wide-area-networks

(WANs) started to evolve.

• 1980s and 1990s - Networks have become a way of life

when performing daily tasks. Internetworks put together

LANs and WANs. Internetworks give an organization a

competitive advantage.



Network EvolutionNetwork Evolution

• 1990s -Users are placing increasing demands on the network.

Current and future networks are providing for integration of

voice, data and video. Client/server model placing increasing

demands on the network.

• 2000+ - Computer networks and the Internet are crucial to

the success of most every business. Wireless networks have

become commonplace. Speeds (data rates) are ever

increasing.



The Basic NetworkThe Basic Network

The basic network allows devices to share informationThe term “Computer Language” refers to Binary code (0’s or 1’s)

The reason that networks were even created is so that we can easily share information and files. Before networks, we had to use floppy disks or other type of physical media to share files.

Before Local Area Networks (LANs), we used mainframes from IBM, Honeywell, DEC, and others. The first LANs used coax connectivity but distance and amount of hosts that could be on a network were limited.

On a basic network, hardware addresses (MAC addresses) are usedto communicate between the hosts.

Hosts communicate with a language referred to as binary code – which is 0’s and 1’s.



The Basic InternetworkThe Basic Internetwork

A router creates an internetwork

In a basic network, hosts use hardware addresses to communicate between each host on the LAN. However, in an internetwork, hosts use logical addresses (IP addresses) to communicate with hosts on a different LAN (other side of the router).

Each connection into a router is a different logical network (broadcast domain).

A network is a connected collection of devices and end systems, such as computers and servers, which can communicate with each other.Networks carry data in many types of environments, including homes, small businesses, and large enterprises. Large enterprises may have various parts such as a Main Office, Remote Locations and BranchOffices along with Home Offices and Mobile Users.



Routing ProtocolsRouting Protocols

When you have more then one router, a routing protocol is used to share network information between the routers. Examples of routing protocols are RIP, RIPv2, IGRP, EIGRP and OSPF.

Routing protocols are used to tell neighbor routers about networks that they are not directly connected to. The routers place these networks in their routing table (map of the internetwork)

Examples of routing protocols are RIP, RIPv2, IGRP, EIGRP and OSPF. EIGRP is a Cisco proprietary routing protocol and is the preferred routing protocol for most networks. You only have Cisco routers in your internetwork, right?

Once all the routers have converged (all have the same routing table), then a routed protocol (typically and hopefully just IP) can send packets through the internetwork.

In smaller networks, you can create static routes instead of using a routing protocol. However, EIGRP works well in small and large networks, so why go through the hassle of static routes? (except for maybe a default route to the Internet).



Internetworking TermsInternetworking Terms

• Collision Domain• Network segment with multiple hosts in which they

all share the same bandwidth. If two hosts transmit

at the same time a collision occurs. Typically

created by using hubs in the network.

• Broadcast Domain• Boundary in which all devices see and participate in

broadcasts sent from hosts and servers. Broadcast

domains created by routers.

By default, switches break up collision domains. This is an Ethernet term used to describe a network scenario wherein one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it. At the same time, a different device tries to transmit, leading to a collision, after which both devices must retransmit, one at a time. Not good—very inefficient! This situation is typically found in a hub environment where each host segment connects to a hub that represents only one collision domain and only one broadcast domain. By contrast, each and every port on a switch represents its own collision domain.

Routers, by default, break up a broadcast domain, which is the set of all devices on a network segment that hear all broadcasts sent on that segment. Breaking up a broadcast domain is important because when a host or server sends a network broadcast, every device on the network must read and process that broadcast—unless you’ve got a router.

Switches create separate collision domains, but a single broadcast domain. Routers provide a separate broadcast domain.



Common Network ComponentsCommon Network Components

Devices used in an internetwork:PC: Computers serve as end pointsInterconnections: i.e. Network Interface Cards (NICs)Hub: Multiple port repeaterBridge: Segments network with hardware addressesSwitch: Multiport bridge with more intelligenceRouter: Segments networks with logical addresses (i.e. IP)

This next section will cover the various Internetworking devices.



MultiMulti--Port Repeater (Hub)Port Repeater (Hub)

One collision domainOne broadcast domain

A hub is really a multiple-port repeater. A repeater receives a digital signal and reamplifies or regenerates that signal, and then forwards the digital signal out all active ports without looking at any data. An active hub does the same thing. Any digital signal received from a segment on a hub port is regenerated or reamplified and transmitted out all ports on the hub. This means all devices plugged into a hub are in the same collision domain as well as in the same broadcast domain.



Transparent BridgesTransparent Bridges

One broadcast domain

Collision domains

Bridges reduce collisions within a broadcast domain while increasing the number of collision domains

Bridge

Bridges and switches read each frame as it passes through the network. The layer-2 device then puts the source hardware address in a filter table and keeps track of which port the frame was received on. This information (logged in the bridge’s or switch’s filter table) is what helps the machine determine the location of the specific sending device.



MultiMulti--Port Bridge (Switch)Port Bridge (Switch)

One broadcast domain

Each port is a separate collision domain

The term bridging was introduced before routers and hubs were implemented, so it’s pretty common to hear people referring to bridges as “switches.”That’s because bridges and switches basically do the same thing—break up collision domains on a LAN. After a filter table is built on the layer-2 device, it will only forward frames to the segment where the destination hardware address is located. If the destination device is on the same segment as the frame, the layer-2 device will block the frame from going to any other segments.If the destination is on a different segment, the frame can only be transmitted to that segment. This is called transparent bridging.



RouterRouter

WAN Services

Each interface is a separate collision domain and broadcast domain

S0/0

E0

E1

Fa0

Here are some points about routers:Routers, by default, will not forward any broadcast or multicast packets.Routers use the logical address in a Network layer header to determine the next hop router to forward the packet to.Routers can use access lists, created by an administrator, to control security on the types of packets that are allowed to enter or exit an interface.Routers can provide layer-2 bridging functions if needed and can simultaneously route through the same interface.Layer-3 devices (routers in this case) provide connections between virtual LANs (VLANs).Routers can provide quality of service (QoS) for specific types of network traffic.



Impact of Applications on the NetworkImpact of Applications on the Network

•Batch Applications•TFTP, FTP•Bandwidth important but not critical•No direct human interaction

•Interactive Applications•Human to Machine Interaction•Inventory Inquiries, Database Updates

•Real-Time Applications•VoIP, Video•Mission Critical Applications (end to end latency critical)•Human to Human Interaction

When considering the interaction between the network and applications that ran on the network, bandwidth was historically the main concern. Batch applications such as FTP, TFTP, and inventory updates would be initiated by a user, then run to completion by the software with no further direct human interaction. Like interactive applications, real time applications such as VoIP and video applications involve human interaction. Because of the amount of information that is transmitted, bandwidth has become critical. In addition, because these applications are time-critical, latency (delay through the network) has become critical. Even variations in the amount of latency can affect the network. Not only is proper bandwidth mandatory, QoS is mandatory. VoIP and video applications must be given the highest priority.



Characteristics of a NetworkCharacteristics of a Network

• Speed• Cost• Security• Availability• Scalability• Reliability• Topology

Speed: Speed is a measure of how fast data is transmitted over the network. Another term to describe speed is data rate.Cost: Cost indicates the general cost of components, installation, and maintenance of the network.Security: Security indicates how secure the network is, including the data that is transmitted over the network. Availability: Availability is a measure of the probability that the network will be available for use when it is required. Scalability: Scalability indicates how well the network can accommodate moreusers and data transmission requirements. If a network is designed and optimized for just the current requirements, it can be very expensive and difficult to meet new needs when the network grows.Reliability: Reliability indicates the dependability of the components (routers, switches, PCs, and so on) that make up the network. This is often measured as a probability of failure, or mean time between failures (MTBF).Topology: In networks, there are two types of topologies: the physical topology, which is the arrangement of the cable, network devices, and end systems (PCs and servers), and the logical topology, which is the path that the data signals take through the physical topology.



Collision and Broadcast DomainsCollision and Broadcast Domains

How many broadcast domains are shown?

How many collision domains are shown?

Two collision domains, two broadcast domains.

A router breaks up both collision domains and broadcast domains and a hub breaks up no collision domains.



How many collision domains are shown?

How many broadcast domains are shown?


Hub HubHub HubHub Hub

Switch Switch

One broadcast domain, six collision domains are shown.

By default, switches break up collision domains with each port, but are one broadcast domain by default.



Which of the hosts can transmit simultaneously without causing collisions?


How many collision and broadcast domains are show?

HubSwitch

Only the hosts connected to the switch can transmit simultaneously without causing collisions.

Four collision domains are shown, one broadcast domain. By default, switches break up collision domains with each port, but they are only one broadcast domain by default.



Hardware and Logical AddressingHardware and Logical Addressing

Communicate on LAN via hardware addresses

Communicate on LAN via hardware addresses

Communicate via logical address

Hardware AddressUniquely identifies a host on a LAN

Logical AddressUniquely identifies a host on an internetwork



Physical TypologiesPhysical Typologies

•Bus: In early networks, computers and other network devices were cabled together in a line using coaxial cable. Modern bus topologies connect the host devices to the bus using twisted-pair wiring.•Ring: Computers and other network devices are cabled together, with the last device connected to the first to form a circle, or ring. This category includes both ring and dual-ring topologies. The physical connection can be made using either coaxial or fiber.•Star: A central cabling device (i.e. switch) connects the computers and other network devices. The physical connection is commonly made using twisted-pair wiring. Most prevalent in today’s networks.•Mesh: There are both full-mesh and partial mesh topologies. In a full-mesh topology each node is connected to every other node for redundancy.



Common Threats to Physical Common Threats to Physical InstallationsInstallations

• Hardware threats

• Environmental threats

• Electrical threats

• Maintenance threats

What should be part of a comprehensive network security plan?*Physically secure network equipment from potential access by unauthorized individuals.

Hardware threats: The threat of physical damage to the router or switch hardware. Mission-critical network equipment should be located in locked room with restricted access.Environmental threats: Threats such as temperature extremes (too hot or too cold) or humidity extremes (too wet or too dry). The room should have dependable temperature and humidity control systems. If possible, remotely monitor and alarm the environmental parameters of the room. Electrical threats: Threats such as voltage spikes, insufficient supply voltage

(brownouts), unconditioned power (noise), and total power loss. Electrical supply problems can be limited by installing uninterruptible power supply (UPS) or backup generator.:Maintenance threats: Maintenance threats include poor handling of equipment (ESD), lack of spares, poor cabling. Clearly label all equipment cabling and secure the cabling to equipment racks to prevent accidental damage, disconnection, or incorrect termination. Do not leave a console connected to and logged into any console port. Always log off administrative interfaces when leaving a station.



Need for Network SecurityNeed for Network Security

• Closed Network – No outside connectivity, networks

designed in this way can be considered safe from

outside attacks. However, internal threats still exist.

• Open Network - Corporate networks require access

to the Internet and other public networks. It is not

uncommon for corporate networks have several access

points to public and other private networks. Securing

open networks is extremely important. Open networks

have not only internal threats but external threats as

well.



Balancing Network SecurityBalancing Network Security

• There is a huge challenge of balancing network

security needs against e-business needs, legal

issues, and government policies.

• The overall security challenge is to find a balance

between two important needs: open networks to

support evolving business requirements and

freedom-of-information initiatives, versus

protection of private, personal, and strategic

business information.



Common AttackCommon Attack

• Denial of Service (DoS): a flood of packets

that are requesting a TCP connection to a

server

company.com

Bad Guy

Internet

65,000 timesSY N

SY NSY N

ACKACK

…CRASH!



Security AppliancesSecurity Appliances• IDS

An intrusion detection system is used to detect several types of

malicious behaviors that can compromise the security and trust of a

computer system. This includes network attacks against vulnerable

services, data driven attacks on applications, host based attacks such

as privilege escalation, unauthorized logins and access to sensitive

files, and malware (viruses, trojan horses and worms).

• IPSAn intrusion prevention system is a computer security device that

monitors network and/or system activities for malicious or unwanted

behavior and can react, in real-time, to block or prevent those

activities. Network-based IPS, for example, will operate in-line to

monitor all network traffic for malicious code or attacks. When an

attack is detected, it can drop the offending packets while still

allowing all other traffic to pass.



The OSI Reference ModelThe OSI Reference Model

(OSI) Open System Interconnection

was created by the

(ISO) International Organization for

Standardization

The OSI reference model was created in the late 1970s, and the main reason the International Organization for Standardization (ISO) released the OSI model was so different vendor networks could work (communicate) with each other. One of the greatest functions of the OSI specifications is to assist in data transfer between disparate hosts, meaning, they enable us to transfer data between a Unix host and a PC or a Mac, for example.The OSI isn’t a physical model, though. Rather, it’s a set of guidelines that application developers can use to create and implement applications that run on a network. It also provides a framework for creating and implementing networking standards, devices, and internetworking schemes.



ISOISOISO is the Greek term for “equal”

• Why the OSI?• It divides the network communication process into smaller

and simpler components, thus aiding component development, design, and troubleshooting

• Changes in the OSI model at one layer do not affect other

layers

• It encourages industry standardization by defining what

functions occur at each layer of the model

Macintosh Unix PC IBM

Advantages of using the OSI layered model include, but are not limited to, the following:Allows multiple-vendor development through standardization of network componentsAllows various types of network hardware and software to communicatePrevents changes in one layer from affecting other layers, so it does not hamper development



File, print, message, database, and application services

End to end connectionRouting

Framing

Physical Topology

Data Translation

Application

Presentation

Session

Transport

Network

Data Link

Physical

OSI Layer & FunctionsOSI Layer & Functions

Dialog control (Maintains, tracks, and closes sessions between applications.)

Concerned with host-to-host communication

Concerned with local and physical network

765

43

21

The OSI reference model has seven layers:Application layerPresentation layerSession layerTransport layerNetwork layerData Link layerPhysical layer



OSI Model (Rational)OSI Model (Rational)

Application

Presentation

Session

Transport

Network

Data Link

Physical

• Manageable• Standardizes interfaces• Ensures interoperability• Promotes modular engineering• Reduces development cycle• Simplifies teaching

Early network development was chaotic. The early 1980s saw tremendous increases in the number and sizes of networks. By the mid-1980s, companies began to experience difficulties from all of the expansions they had made. It became more difficult for networks using different specifications and implementations to communicate with one another. To address the problem of networks being incompatible and unable to communicate with one another, the International Organization forStandardization (ISO) researched different network schemes. As a result of this research, the ISO created a model that would help vendors create networks that would be compatible with, and operate with, other networks, hence the OSI reference model.The OSI reference model was released in 1984. It provided vendors with a set of standards that ensured greater compatibility and interoperability between the various types of network technologies produced by companies around the world. The OSI model is considered the best tool available for teaching people about data networks.



OSI Model (Remembering)OSI Model (Remembering)

Application

Presentation

Session

Transport

Network

Data Link

Physical

Easy way to remember the order of the OSI reference model:All People Seem To Need Data Processing.Or in the reverse order:Please Do Not Teach Sales People Anything. ☺Translates to:

Sentences to help remember the layers of the OSI Reference Model:

Please Do Not Throw Sausage Pizza Away.

Or

All People Seem To Need Data Processing.



Application LayerApplication Layer

Application

Presentation

Session

Transport

Network

Data Link

Physical

Remote LoginTelnet, rlogin

File TransferTFTP, FTP

EmailSimple Mail Transfer Protocol (SMTP)

Network Management SNMP

Internet BrowsingHTTP, HTTPS

Closest to the user. Provides services directly to applications. Does not provide any services to other OSI layers

Name ManagementDNS

The Application layer of the OSI model marks the spot where users actually communicate to the computer. This layer is responsible for identifying and establishing the availability of the intended communication partner, and determining if sufficient resources for the intended communication exist.

A vast array of protocols combine at the DoD model’s Process/Application layer to integrate the various activities and duties spanning the focus of the OSI’s corresponding top three layers (Application, Presentation, and Session).



Presentation LayerPresentation Layer

Application

PresentationSession

Transport

Network

Data Link

Physical

Rich Text Format

MPEG files

Musical Instrument Digital Interface

Quick Time Movies

Provides for code formatting, conversion and representation. Ensures that information sent by the application layer of one system is readable by another. Can include encryption services.

JPEG files

The Presentation layer gets its name from its purpose: It presents data to the Application layer and is responsible for data translation and code formatting.This layer is essentially a translator and provides coding and conversion functions. A successful data-transfer technique is to adapt the data into a standard format before transmission.



Session LayerSession Layer

Application

Presentation

SessionTransport

Network

Data Link

Physical

XWindow

Remote Procedure Call (RPC)

Network File System (NFS)

Structured Query Language (SQL)

Establishes, manages and terminates sessions between applications. Coordinates service requests and responses when applications communicate between different hosts. Responsible for inter-host communication.

The Session layer is responsible for setting up, managing, and then tearing down sessions between Presentation layer entities. This layer also provides dialogue control between devices, or nodes.



Transport LayerTransport Layer

Establishes a reliable communication stream between a pair of systems. Responsible for end-to-end communications. Deals with issues such as reliable service and flow control.

Application

Presentation

Session

Transport

Network

Data Link

Physical

Provides mechanisms for the establishment, maintenance, and termination of virtual circuits.

User Datagram Protocol (UDP)

Transmission Control Protocol (TCP)

The Transport layer segments and reassembles data into a data stream. Services located in the Transport layer both segment and reassemble data from upper-layer applications and unite it onto the same data stream. They provide end-to-end data transport services and can establish a logical connection between the sending host and destination host on an internetwork.Provides mechanisms for the establishment, maintenance, and termination of virtual circuits. The Transport layer can use positive acknowledgement and retransmission to ensure reliable delivery.Information flow control. The Transport Layer sends Segments between peer transport layers.



Network LayerNetwork Layer

Establishes the connection between two end nodes and provides path selection. This is where routing takes place.

Application

Presentation

Session

Transport

NetworkData Link

Physical

PDU: Packet

TCP/IP Suite•IP – Internet Protocol•ICMP – Internet Control Message

Protocol•ARP – Address Resolution Protocol•RARP – Reverse Address Resolution

Protocol

The Network layer (also called layer 3) manages devices addressing, tracks the location of devices on the network, and determines the best way to move data, which means that the Network layer must transport traffic between devices that aren’t locally attached. Routers (layer-3 devices) are specified at the Network layer and provide the routing services within an internetwork.

Device addressingTracks locations of devices on the networkDetermines the best way to move data

PDU at the Network layer is called “Packet”.

The Network layer sends Packets between peer network layers.



Data Link LayerData Link Layer

Provides transport of data across a physical link. Specifies topology and hardware (physical) addressing.

Application

Presentation

Session

Network

Transport

Data LinkPhysical

Ethernet

Frame Relay

HDLC

PPP

The Data Link layer provides the physical transmission of the data and handles error notification, network topology, and flow control.

This means the Data Link layer will ensure that messages are delivered to the proper device on a LAN using hardware addresses, and translates messages from the Network layer into bits for the Physical layer to transmit.

The Data Link layer sends Frames between peer data link layers.



Logical Link Control (LLC)

Media access control (MAC)

802.2802.3802.11

IEEE Data Link SubIEEE Data Link Sub--LayersLayers

PDU: Frame

The IEEE has divided this layer into two sub-layers:The MAC sublayerThe LLC sublayer

The IEEE Ethernet Data Link layer has two sublayers:

Media Access Control (MAC) 802.3This defines how packets are placed on the media. Contention media access is “first come/first served” access where everyone shares the same bandwidth—hence the name. Physical addressing is defined here, as well as logical topologies.

Logical Link Control (LLC) 802.2This sublayer is responsible for identifying Network layer protocols and then encapsulating them. An LLC header tells the Data Link layer what to do with a packet once a frame is received.

PDU at the Data Link layer is called “Frame”.



MAC AddressMAC Address

MAC address is burned into ROM on a network interface card

0080.0c45. 6789

24 bits24 bits

Vendor CodeVendor Code Serial NumberSerial Number

0000.0c98.7654

E0: 0000.0c45.6789

S0

0080.0c45.6789

Unique for each local area interface48-bit addresses

Expressed as 12 hexadecimal digits0000.0c12.abcd

First six hexadecimal digits contain manufacturer identification(vendor code) also called Organizational Unique Identifier (OUI).Manufacturer IDs administered by IEEE



Physical LayerPhysical Layer

Application

Presentation

Session

Transport

Network

Data Link

Physical

Specifies electrical signaling and hardware interface. This includes voltage levels, data rates, maximum transmission distances and physical connectors

EIA/TIA-449

HSSI

EIA-530

V.35

Finally arriving at the bottom, we find that the Physical layerdoes two things: It sends bits and receives bits. Bits come only in values of 1 or 0—a Morse code with numerical values.

The physical layer defines the electrical, mechanical, procedural and functional specifications for:activatingmaintainingdeactivating

the physical link between end systems.

The Physical layer sends Bits between peer physical layers.



Peer to Peer CommunicationPeer to Peer Communication

Each layer of the OSI Model communicates with its peer layer.

Segments

Bits

Packets

Frames

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Each layer of the OSI model at the source must communicate with its peer layer at the destination. During the protocols ateach layer exchange packets of information called protocol data units (PDUs) between peer layers.

Bits are sent between physical layer peers.Frames are sent between data link layer peers.Packets are sent between transport layer peers.Segments are sent between transport layer peers.



TCP/IP Stack compared to OSI TCP/IP Stack compared to OSI

Application

Presentation

Session

Transport

Network

Data Link

Physical

Process/Application

Host to Host

Internet

NetworkAccess

The TCP/IP model is basically a condensed version of the OSI model—it’s composed of four, instead of seven, layers:

Process/Application layerTransport layerInternet layerNetwork Access layer

The OSI model and the TCP/IP stack were developed, by different organizations, at approximately the same time as a means to organize and communicate the components that guide the transmission of data.



Data EncapsulationData Encapsulation

Transport

Data Link

Physical

Network

Upper Layer Data

Upper Layer DataTCP Header

DataIP Header

DataLLC Header

0101110101001000010

DataMAC Header

Presentation

Application

Session

Segments

Packets

Bits

FramesFCS

Data

Following the data stream:Alphanumeric user input is converted to data for transmission on the network (At the upper layers)Data is converted to segments, which allow hosts to reliably communicate (At the Transport Layer)Segments are converted to packets or datagrams with a source and destination logical address (At the Network layer)Packets or datagrams are converted to frames for transmission over an interface to the network (At the Data Link Layer)Frames are converted to bits, and uses a synchronization and clocking function (At the Physical Layer)

When going from layer 7 to layer 1, encapsulation occursWhen going from layer 1 to layer 7, de-encapsulation occurs



Ethernet TechnologiesEthernet Technologies

Chapter 1 Continued

Ethernet is a contention media access method that allows all hosts on a network to share the same bandwidth of a link. Ethernet is popular because it’s readily scalable, meaning it’s comparatively easy to integrate new technologies, like FastEthernet and Gigabit Ethernet, into an existing network infrastructure. It’s also relatively simple to implement in the first place, and with it, troubleshooting is reasonably straightforward. Ethernet uses both Data Link and Physical layer specifications



Physical

MAC layerEt

hern

e t

100b

aseT

X

10B

aseT

IEEE 802.3

10B

ase5

10B

ase2

100b

aseF

X

802.3 Specifications for 10mb Ethernet

802.3u Specifications for 100mb FastEthernet

100b

aseT

4

10B

aseF

DIX Standard

LLC layer IEEE 802.2

1000

base

TX

1000

base

FX

1000

base

T4

802.3ab\z Specifications for 1000mb Gigabit Ethernet

IEEE 802.3 LANIEEE 802.3 LAN

Ethernet was first implemented by a group called DIX (Digital, Intel, and Xerox).They created and implemented the first Ethernet LAN specification, which the IEEE used to create the IEEE 802.3 Committee. This was a 10Mbps network that ran on coax, twisted-pair, and fiber physical media.The IEEE extended the 802.3 Committee to new committees known as 802.3U (FastEthernet) and 802.3aband 802.3z (Gigabit Ethernet) and 802.3ac (10-Gig). These are both specified on twisted-pair and fiber physical media.



Preamble7 Bytes

DA6 Bytes

SA6 Bytes

Ether-Type2 Bytes

Data46-1500

FCS4 Bytes

Ethernet_II

802.3_Ethernet (IEEE 802.3 RAW)

Preamble7 Bytes

DA6 Bytes

SA6 Bytes

Length2 Bytes

Data46-1500

FCS2 Bytes

Frame TypesFrame Types

SOF

SOF

Ethernet at the Data Link layer is responsible for Ethernet addressing, commonly referred to as hardware addressing or MAC addressing. Ethernet is also responsible for framing packets received from the Network layer and preparing them for transmission on the local network through the Ethernet contention media access method. There are four different types of Ethernet frames available:Ethernet_IIIEEE 802.3IEEE 802.2SNAP

The function of Ethernet stations is to pass data frames betweeneach other using a group of bits known as a MAC frame format.

This provides error detection from a cyclic redundancy check (CRC). But remember—this is error detection, not error correction.



802.3 with LLC (802.2)802.3 with LLC (802.2)

Dest SAP Source SAP802.2 Ctrl

Dest SAP

AA

Source SAP

AA

SNAPCtrl03

OUI ID

EtherType

802.3_EthernetDA6 Bytes

SA6 Bytes

LengthBytes

DATA FCS

Since the 802.3 Ethernet frame cannot by itself identify the upper-layer (Network) protocol, it obviously needs some help. The IEEE defined the 802.2 LLC specifications to provide this function and more.

802.2 uses Destination and Source Service Access Points (SAP’s) to identify the Network layer protocol

The SNAP frame has its own protocol field to identify the upper-layer protocol. This is really a way to allow an Ethernet_II Ether-Type field to be used in an 802.3 frame.



EthernetEthernet

Ethernet is a physical star, logical bus technology

Physical star topology means that the network is physically connected in the center

Physical star topology means that the network is physically connected in the center, as shown in the hub diagram in this slide.The logical bus means the signal must run from the beginning of a network segment to the end, and everyone on that segment must listen to the signal on the bus.Switches break up these segments into smaller logical bus’s



CSMA/CDCSMA/CD

• Carrier Sense, Multiple Access with Collision Detection (CSMA/CD)

• Statistical limit to the number of devices on segment

As devices increase:• Collisions increase• Effective bandwidth decreases (through-put)• Increased delay• Increased congestion

Ethernet networking uses Carrier Sense Multiple Access with Collision Detect (CSMA/CD), a protocol that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium. CSMA/CD was created to overcome the problem of those collisions that occur when packets are transmitted simultaneously from different nodes.

Used in Half-Duplex Ethernet networks.Half-duplex is single pair for both transmit and receive.If a collision does occur, the transmitting host sends an extended jam

signal, which tells all hosts to stop transmitting.Backoff algorithm is the retransmission delay that is enforced when a

collision occurs. This causes global synchronization which reduces performance.



Duplex OverviewDuplex OverviewDuplex Overview

802.3 Half duplex (CSMA/CD)Unidirectional data flowHigher potential for collisionHubs connectivity One wire pair Shared collision domainLower Effective Throughput

Hub

Full duplexPoint-to-point onlyAttached to dedicated switched portRequires full-duplex support on both endsCollision free Collision detect circuit disabledTwo wire pair

Half-duplex Ethernet is defined in the original 802.3 Ethernet and uses only one wire pair with a digital signal running in both directions on the wire.It also uses the CSMA/CD protocol to help prevent collisions and to permit

retransmitting if a collision does occur. If a hub is attached to a switch, it must operate in half-duplex mode because the end stations must be able to detect collisions. Half-duplex Ethernet—typically 10BaseT—is only about 30 to 40 percent efficient as Cisco sees it, because a large 10BaseT network will usually only give you 3- to 4Mbps—at most.But full-duplex Ethernet uses two pairs of wires, instead of one wire pair like half duplex. And full duplex uses a point-to-point connection between the transmitter of the transmitting device and the receiver of the receiving device. This means that with full duplex data transfer, you get a faster data transfer compared to half-duplex. And because the transmitted data is sent on a different set of wires then the received data, no collisions will occur—sweet!

Full-Duplex is collision freeHalf-Duplex is subject to collisionsFull-Duplex provides higher throughput than Half-Duplex Ethernet of the

same bandwidthHalf-Duplex operates in a shared collision domainFull-Duplex operates in a private collision domain



Straight

Cisco DTE device(Ethernet 0)

12345678

12345678

Switch device(Ethernet Interface)

RJ-45 pinsEIA/TIA 568B

Pair 4

Pair 1Pair 1

Pair 3

Pair 4

Pair 3Pair 2

Pair 2

Pair 4

Pair 1Pair 1

Pair 3

Pair 4

Pair 3Pair 2

Pair 2

RJRJ--45 Wiring and CAT 5 Cables45 Wiring and CAT 5 Cables

This type of Ethernet cable is used to connect:-Host to switch or hub-Router to switch or hubFour wires are used in straight-through cable to connect Ethernet devices. It is relatively simple to create this type of cable.



RJRJ--45 Wiring and Cables45 Wiring and Cables

RJ-45 pinsEIA/TIA 568B

Cross over


12345678

12345678


Pair 4

Pair 1Pair 1

Pair 3

Pair 4

Pair 3Pair 2

Pair 2

Pair 4

Pair 1Pair 1

Pair 3

Pair 4

Pair 3Pair 2

Pair 2

Hub

This type of Ethernet cable can be used to connect:-Switch to switch-Hub to hub-Host to hostThe same four wires are used in this cable as in the straight-through cable, but we just connect different pins together.



Console CablesConsole Cables

PC or other DTE device (Com 1)

87654321

Rolled

TxDDTRRTS

GNDGND

CTSDSR/CDRxD

Cisco DTE device(Console)

RTSDTRTxDGNDGNDRxD

DSR/CDCTS

12345678

RJ-45 pinsand signals

Adapter

DB 9

Although this type isn’t used to connect any Ethernet connections together, you can use a rolled Ethernet cable to connect a host to a router console serial communication (com) port.If you have a Cisco router or switch, you would use this cable to connect your PC running HyperTerminal to the Cisco hardware. Eight wires are used in this cable to connect serial devices.

As you can see, Cisco console cables are rolled cables where pin 1 maps to pin 8, pin 2 maps to pin 7 and so on.



Chapter 1 LabChapter 1 Lab

Written Lab 1.1

Open your lab books and complete written lab 1.1



IP RoutingIP Routing

Chapter 5

In this chapter, we’re to discuss the IP routing process. This is an important subject to understand since it pertains to all routers and configurations that use IP. IP routing is the process of moving packets from one network to another network using routers. And by routers, we mean Cisco routers, of course!

This chapter correlates directly with chapter 5 of the SybexCCNA Study Guide.



To route a router need to know:• Remote Networks• Neighbor Routers• All Possible routes to remote network• The absolute best route to all remote

networks• Maintain and verify the routing information

What is Routing?What is Routing?

D C B A

Once you create an internetwork by connecting your WANs and LANs to a router, you then need to configure logical network addresses, such as IP addresses, to all hosts on the internetwork so that they can communicate across that internetwork.The term routing is used for taking a packet from one device and sending it through the network to another device on a different network. Routers don’t care about hosts—they only care about networks and the best path to each network. The logical network address of the destination host is used to get packets to a network through a routed network, then the hardwareaddress of the host is used to deliver the packet from a router to the correct destination host.



Basic Path SelectionBasic Path Selection

What interface will the router send out a packet if it has destination address of 10.10.10.18?

Fa0/0

Fa0/2

Fa0/1

S0/010.10.20.2 /24

10.10.10.2 /24

10.10.40.1 /24

10.10.30.1 /24

The router will packet switch the packet to the FastEthernet 0/0 interface and then frame it and send it out the LAN



Longest Match RuleLongest Match Rule

Ping Outgoing Interface

10.1.1.9

10.4.4.4

10.1.4.7

209.41.3.7

Routers will compare the destination ip address with entries in their route table and choose the path that provides the longest applicable match.

Assuming you want to ping the addresses as indicated in the table, through which interface will the packets be forwarded?

Route Outgoing Interface

10.0.0.0/8 E1

10.1.0.0/16 E0

10.1.4.0/24 E2

0.0.0.0/0 E3

E0

E1

E2

E3

Ping to 10.1.1.9 would be sent out of E0Ping to 10.4.4.4 would be sent out of E1Ping to 10.1.4.7 would be sent out of E2Ping to 209.41.3.7 would be sent out of E3

Don’t confuse this with Administrative Distance. Administrative Distance is how the best routes are selected for the route table.If there are multiple entries to the same network, the longest match rule always wins. Look at the prefix



Simple IP RoutingSimple IP Routing

172.16.1.0

BA

172.16.2.0

172.16.2.2

172.16.1.2172.16.2.1 172.16.1.1

e0 e0

>ping 172.16.1.2>ping 172.16.1.2

B

172.16.3.1 172.16.3.2

s0s0

Host A

Host B

The IP routing process is fairly simple and doesn’t change, regardless of the size of network you have. For an example, we’ll describe step by step what happens when Host A wants to communicate with Host B on a different network.In this example, a user on Host A pings Host B’s IP address.



show ip show ip arparp

What will Router1 do when it receives the above frame?

Router1# show ip arp

Protocol Address Age(min) Hardware Adddr Type Interface

Internet 192.168.10.2 9 0000.0c09.ff76 ARPA FastEthernet0/0Internet 192.168.30.9 8 0000.0c89.a400 ARPA FastEthernet0/1Internet 192.168.20.3 - 0000.0c67.ue29 ARPA FastEthernet0/0Internet 192.168.30.3 9 0000.0c00.142d ARPA FastEthernet0/2Internet 192.168.50.5 - 0000.0c35.11p8 ARPA FastEthernet0/1Internet 192.168.40.2 - 0000.0c36.ku57 ARPA FastEthernet0/2

0000.0c09.ff76 192.168.10.2 0000.0c67.ue29 192.168.30.3Source MAC Source IP Destination MAC Destination IPData Frame

Answer on next slide



Answer to Previous SlideAnswer to Previous Slide

0000.0c00.142d192.168.30.3

F0/2

F0/1

F0/0192.168.40.2

0000.0c36.ku57192.168.20.3

0000.0c67.ue29

192.168.10.20000.0c09.ff76

192.168.50.5

0000.0c89.a400192.168.30.9

0000.0c35.11p8

Dest Mac0000.0c00.142d

Source Mac0000.0c36.ku57

Dest Mac0000.0c67.ue29

Source Mac0000.0c09.ff76

Router1 will strip off the source MAC address and replace it with the MAC address 0000.0c36.6965Router1 will strip off the destination MAC address and replace it with the MAC address 0000.0c07.4320Router1 will forward the data packet out interface Fa0/2



Host A Web browses to the HTTP Host A Web browses to the HTTP ServerServer……..

3. The destination port number in a segment header will have a value of __

1. The destination address of a frame will be the _______________________

2. The destination IP address of a packet will be the IP addressof the ________________________________

A BS0

S1E0 E0

Host A HTTP Server

This slide represents how segments, packets and frames are used to send data from HostA to the HTTP server. It’s important to remember that frames are “ALWAYS” on a local network and hardware addressees are used.Packets are used to route a segment from one network to another networkSegments are used to rebuild a datastream on a remote host, in this case, the HTTP server.

3. The destination port number in a segment header will have a value of 80

1. The destination address of a frame will be the MAC address of the E0 interface of the Lab_A router

2. The destination IP address of a packet will be the IP addressof the network interface of the HTTP server



How will the frames sent from host A be How will the frames sent from host A be addressed when the frames reach host B?addressed when the frames reach host B?

192.168.23.100c0.6AE6.EAEF

Router

192.168.20.500c0.0c36.f892

192.168.23.200a0.3D3A.66BC

192.168.20.600a0.3C22.1122

A B

Final Frame received by Host BSource MAC = 00c0.0c36.f892Destination MAC = 00a0.3C22.1122Source IP = 192.168.23.2Destination IP – 192.168.20.6

Initial Frame sent by Host ASource MAC = 00a0.3d3a.66bcDestination MAC = 00c0.6ae6.eaefSource IP = 192.168.23.2Destination IP – 192.168.20.6



Host A is sending to Host BHost A is sending to Host B

How will Router1 handle the data received from Host A?

Router1# show ip arpProtocol Address Age(min) Hardware Adddr Type InterfaceInternet 192.168.10.2 9 0000.0c09.ff76 ARPA FastEthernet0/0Internet 192.168.30.9 8 0000.0c89.a400 ARPA FastEthernet0/1Internet 192.168.20.3 - 0000.0c67.ue29 ARPA FastEthernet0/0Internet 192.168.30.3 9 0000.0c00.142d ARPA FastEthernet0/2Internet 192.168.50.5 - 0000.0c35.11p8 ARPA FastEthernet0/1Internet 192.168.40.2 - 0000.0c36.ku57 ARPA FastEthernet0/2

Router 1

Switch 1

Switch 2

Switch 3Host A

192.68.10.2 Host B192.68.30.3

Host C192.68.50.5

Fa0/0

Fa0/2

Fa0/1

An ethernet frame will be sent out fa0/2 with a destination address of 0000.0c07.4320 since 192.168.40.5 is in Router1’s ARP table.



172.16.3.2

SO

Static RoutesStatic Routes

172.16.1.0

B172.16.3.1

A B

Stub Network

172.16.2.0

SOA

Routes must be unidirectional

Static routing occurs when you manually add routes in each router’s routing table. There are pros and cons to static routing, but that’s true for all routing processes.Things that are good about static routing:-No overhead on the router CPU-No bandwidth usage between routers-Security (because the administrator can only allow routing to certain networks)Things that aren’t so good about static routing:-The administrator must really understand the internetwork and how each router is connected super well in order to configure routes correctly.-If a network is added to the internetwork, the administrator has to add a route to it on all routers—by hand.-It just won’t work for you in large networks because maintaining it would be a full-time job in itself.



ip route 172.16.1.0 255.255.255.0 172.16.3.2orip route 172.16.1.0 255.255.255.0 s0

Static Route ExampleStatic Route Example

172.16.3.2

SO

172.16.1.0

B172.16.3.1

A B

Stub Network

172.16.2.0

SO

This slide shows an example of a simple static route command.

Static routes are used to send all unknown destination packets to a next hop router.



Default RoutesDefault Routes

172.16.3.2

SO

172.16.1.0

B172.16.3.1

A B

Stub Network

172.16.2.0

SO

ip route 0.0.0.0 0.0.0.0 172.16.3.1 ip classless

We use default routing to send packets with a remote destination network not in the routing table to the next-hop router. You can only use default routing on stub networks—those with only one exit port out of the network.



Default Route ExampleDefault Route Example

• ip route 0.0.0.0 0.0.0.0 172.16.3.2• ip route 0.0.0.0 0.0.0.0 s0

this works too….• ip default-network 172.16.3.0 (EIGRP)• default-information originate (OSPF)

172.16.3.2

S0

Internal Network

172.16.3.1Gateway

S0ISP

This slide shows multiple examples to configure default routes.

The “ip route 0.0.0.0 0.0.0.0 172.16.3.2” has an Administrative Distance of 1.The “ip route 0.0.0.0 0.0.0.0 s0” has an Administrative Distance of 0 just as a connected interface.

Administrative Distance will be discussed later.



Routing LoopsRouting Loops

172.16.3.2

SO

B172.16.3.1A B

SO



Be careful NOT create routing loops!



Larger Static Route ExampleLarger Static Route Example

config tip route 0.0.0.0 0.0.0.0 172.16.40.1ip classless

E0 E0

S1 S1S0

S0

S0

S0

config tip route 172.16.10.0 255.255.255.0 172.16.30.1ip route 172.16.20.0 255.255.255.0 172.16.30.1ip route 172.16.50.0 255.255.255.0 172.16.40.2

10

20

30

50

40

.1

.2

.1

This slide shows an example of using both static and default routing on a network with four router. Every router would need to have the routing tables built.



Chapter 5 LabChapter 5 Lab

Hands-on Lab 5.1

Open your lab books and perform hands-on lab 5.1.



Dynamic RoutingDynamic Routing

Chapter 5 Continued

Dynamic routing is when protocols are used to find and update routing tables on routers. True—this is easier than using static or default routing, but it’ll cost you in terms of router CPU processes and bandwidth on the network links. A routing protocol defines the set of rules used by a router when it communicates between neighbor routers.



• Routing protocols are used between routers to: • Determine the path of a packet through a network• Maintain routing tables• Examples?

• RIP, EIGRP, OSPF

• Routed protocols are:• Assigned to an interface• Once the path is determined by the Routing protocol, determines

method of delivery• Examples?

• IP, IPX

What is a Routing Protocol?

A routing protocol is used by routers to dynamically find all the networks in the internetwork and to ensure that all routers have the same routing table.Basically, a routing protocol determines the path of a packet

through an internetwork. Examples of routing protocols are RIP, IGRP, EIGRP and OSPF.

Okay—once all routers know about all networks, a routed protocol can be used to send user data (packets) through the established enterprise. Routed protocols are assigned to an interface and determine the method of packet delivery. Examples of routed protocols are IP and IPX.



Autonomous System 1 Autonomous System 2

IGPs: RIP, IGRPEIGRP, OSPF EGPs: BGP

Routing ProtocolsRouting Protocols

• An autonomous system is a collection of networks under a common administrative domain.

• IGPs operate within an autonomous system.• EGPs connect different autonomous systems.

There are two types of routing protocols used in internetworks: interior gateway protocols (IGPs) and exterior gateway protocols (EGPs).IGPs are used to exchange routing information with routers in the same autonomous system (AS). An AS is a collection of networks under a common administrative domain, which basically means that all routers sharing the same routing table information are in the same AS.EGPs are used to communicate between ASs. An example of an EGP is Border Gateway Protocol (BGP).


Classful routing means that all devices in the network must use the same subnet mask.


ClassfulClassful Routing OverviewRouting Overview

• Classful routing protocols do not include the subnet mask with the route advertisement.

• Within the same network, consistency of the subnet masks is assumed.

• Summary routes are exchanged between foreign networks.

• Examples of classful routing protocols:• RIP Version 1 (RIPv1)• IGRP


Prefix routing does send subnet mask information with the route updates. This is called classless routing.


Classless Routing OverviewClassless Routing Overview

• Classless routing protocols include the subnet mask with the route advertisement.

• Classless routing protocols support Variable-Length Subnet Masking (VLSM).

• Advantages of classless routing:• Fewer IP addresses are wasted• Summarization can be manually controlled

within the routing protocol• Examples of classless routing protocols:

• RIP Version 2 (RIPv2)• EIGRP• OSPF• IS-IS



Classes of Routing ProtocolsClasses of Routing Protocols

A

B

C

D

A

B

C

DDistance VectorHybrid Routing

Link State

There are three classes of routing protocols:Distance vector: The distance-vector protocols find the best path to a remote network by judging distance. Each time a packet goes through a router, that’s called a hop. The route with the least number of hops to the network is determined to be the best route. The vector indicates the direction to the remote network. Both RIP and IGRP are distance-vector routing protocols. They send the entire routing protocol to directly connected neighbors.Link state: In link-state protocols, also called shortest-path-first protocols, the routers each create three separate tables. One of these tables keeps track of directly attached neighbors, one determines the topology of the entire internetwork, and one is used as the routing table. Link-state routers know more about the internetwork than any distance-vector routing protocol. OSPF is an IP routing protocol that is completely link state. Link State protocols send updates containing the state of their own link to all other routers on the network. Hybrid: The hybrid protocols use aspects of both distance vector and link state—for example, EIGRP.



Routing Protocol Comparison ChartRouting Protocol Comparison Chart

This slide shows the various routing protocols available and their characteristics.

RIPv2 is exactly like RIPv1, except that it send out subnet maskinformation with the route table updates. This allows RIPv2 to support VLSM networks and discontiguous networks.



Administrative Distance: Administrative Distance: Ranking RoutesRanking Routes

Default Administrative Distance:Directly Connected: 0Static Route: 1RIP: 120IGRP: 100EIGRP: 90OSPF: 110

A

B

D

C

E

IGRP Administrative Distance = 100

RIP Administrative Distance = 120

I need to send data to Network

E. Routers B and C will get it there, but which

route is best?

The Administrative Distance (AD) is used to rate the trustworthiness of routing information received on a router from a neighbor router. An administrative distance is an integer from 0 to 255, where 0 is the most trusted and 255 means no traffic will be passed via this route.If a router receives two updates listing the same remote network, the first thing the router checks is the AD. If one of the advertised routes has a lower AD than the other, then the route with the lowest AD will be placed in the routing table.If both advertised routes to the same network have the same AD, then routing protocol metrics (such as hop count or bandwidth of the lines) will be used to find the best path to the remote network. The advertised route with the lowest metric will be placed in the routing table. But if both advertised routes have the same AD as well as the same metrics, then the routing protocol will load-balance to the remote network.



Distance Vector MetricsDistance Vector Metrics

• IP RIP uses only Hop count

• IGRP uses a composite metric of

bandwidth and delay of the line by

default. MTU, Reliability and Load can be

administratively configured

Metrics are used to determine the best path to a remote network if more then one path exists.



Distance VectorDistance VectorDistance Vector

CC BB AADD

RoutingTable

RoutingTable

RoutingTable

RoutingTable

RoutingTable

RoutingTable

RoutingTable

RoutingTable

Distance—How farVector—In which direction

Distance—How farVector—In which direction

• Routers pass periodic copies of their routing table to neighboring routers and accumulate distance vectors.

The distance-vector protocols find the best path to a remote network by judging distance.

Each time a packet goes through a router, that’s called a hop. With RIP, the route with the least number of hops to the network is determined to be the best route. IGRP utilizes a more complex algorithm for determining the best route. It is a combination of bandwidth, delay, load, reliability and mtu.

The vector indicates the direction to the remote network. Both RIP and IGRP are distance-vector routing protocols.

Distance vector routing protocols are sometimes referred to as routing by rumor.Distance vector algorithms do not allow a router to know the exact topology of an internetwork.This information is somewhat analogous to the information found on signs at a highway intersection. A sign points toward a road leading away from the intersection and indicates the distance to the destination.

Further down the highway, another sign also points toward the destination, but now the distance to the destination is shorter.

As long as each successive point on the path shows that the distance to the destination is successively shorter, the traffic is following the best path.



AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0

Routing TableRouting Table

172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 00


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

Discovering RoutesDiscovering RoutesDiscovering Routes

Routers, when powered up and the interfaces are enabled, have only their directly connected networks in the routing table



AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 00


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011

11172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.012 S1

S0S0S0

Discovering RoutesDiscovering RoutesDiscovering Routes

Router C is directly connected to network 172.16.4.0 with a distance of 0. Router A’s path to 172.16.4.0 is through Router B, with a hop count of 2.



Routing LoopsRouting LoopsRouting Loops

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 00


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011

11172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.012 S1

S0S0S0

XX

Router C has detected the failure of network 172.16.4.0 and stops routing packets out its E0 interface. However, Router A has not yet received notification of the failure and still believes it can access network 172.16.4.0 through Router B.

Router A’s routing table still reflects a path to network 10.4.0.0 with a distance of 2.



Symptom: Counting to InfinitySymptom: Counting to InfinitySymptom: Counting to Infinity

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.0E0E0 00

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 S0 22


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0E0

E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.0

11

33172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.014 S1

S0S0S0

XX

Because Router B’s routing table indicates a path to network 172.16.4.0, Router C believes it now has a viable path to 172.16.4.0 through Router B. Router C updates its routing table to reflect a path to network 172.16.4.0 with a hop count of 2.



Symptom: Counting to InfinitySymptom: Counting to InfinitySymptom: Counting to Infinity

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 33


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011

44172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.015 S1

S0S0S0

XX

Router A receives the new routing table from Router B, detects the modified distance vector to network 172.16.4.0, and recalculates its own distance vector to network 172.16.4.0



Solution: Defining a MaximumSolution: Defining a MaximumSolution: Defining a Maximum

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 1616


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011 172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.01

16 S1S0S0

S0 1616

XX

To avoid prolonging the count-to-infinity time span, distance vector protocols define infinity as some maximum number.

This number refers to a routing metric, such as a hop count.



Solution: Split HorizonSolution: Split HorizonSolution: Split Horizon

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 00


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011

11172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.012 S1

S0S0S0

XX

Periodic Update

Network 4 not sent in update

The rule of Split Horizon states: Never advertise a route out of the interface through which you learned it.



Solution: Route PoisoningSolution: Route PoisoningSolution: Route Poisoning

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 1616


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011

1616172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.012 S1

S0S0S0

XX

Route Poisoning sends a “infinite hop count” for a downed link.



Solution: Poison ReverseSolution: Poison ReverseSolution: Poison Reverse

AA BB CC

172.16.1.0 172.16.2.0 172.16.3.0 172.16.4.0

E0 S0 S0 S1 S0 E0


172.16.2.0172.16.2.0

172.16.3.0172.16.3.000

00S0S1


172.16.3.0172.16.3.0 S0 00

172.16.4.0172.16.4.0 E0 1616


172.16.1.0172.16.1.0

172.16.2.0172.16.2.0E0S0

00

172.16.1.0172.16.1.0

172.16.4.0172.16.4.011

1616172.16.1.0172.16.1.0 S0 22

172.16.2.0172.16.2.0 S0 11172.16.3.0172.16.3.0

172.16.4.0172.16.4.01

16 S1S0S0

S0

XX

Poison Reverse is an acknowledgement to a route poison. Poison reverse overrides the split-horizon solution

Poison Reverse states: Once you learn of a route through an interface, advertise it as unreachable back through that same interface.



• The router keeps an entry for the “possibly down state” in the network, allowing time for other routers to recompute for this topology change.

• Hold-down timers are used to prevent regular update messages from inappropriately reinstating a route that may have gone bad.

Holddown TimersHolddown Timers

A B C E0S0S1S0S0E0

10.1.1.1 10.2.1.1 10.3.1.1 10.4.1.1

Network 10.4.1.1 is Down….. Then Back Up……Then Back Down…..

Update After Hold Down Time

Update After Hold Down Time

Network 10.4.1.1 is unreachable

Hold-down timers are used to prevent regular update messages from inappropriately reinstating a route that may have gone bad.Hold-downs tell routers to hold any changes that might affect routes for some period of time. The hold-down period is usually calculated to be just greater than the period of time necessary to update the entire network with arouting change.



Chapter 5 ContinuedChapter 5 Continued

RIP Version 1 and

Version 2



64kbps

T1

T1 T1

• Hop count metric selects the path, 16 is unreachable

• Full route table broadcast every 30 seconds

• Load balance maximum of 6 equal cost paths (default = 4)

• RIPv2 supports VLSM and Discontiguous networks

RIP Overview

Routing Information Protocol (RIP) is a true distance-vector routing protocol. It sends the complete routing table out to allactive interfaces every 30 seconds. RIP only uses hop count to determine the best way to a remote network, but it has a maximum allowable hop count of 15 by default, meaning that 16 is deemed unreachable. RIP works well in small networks, but it’s inefficient on large networks with slow WAN links or on networks with a large number of routers installed.RIP version 1 uses only classful routing, which means that all devices in the network must use the same subnet mask.



Router(config)# router rip

Router(config-router)# network network-number*

network 172.16.0.0network 192.168.10.0

router ripnetwork 172.16.0.0network 10.0.0.0

router rip

*Network is a classful network address. Every device on network uses the same subnet mask

172.16.10.0 192.168.10.010.3.5.0

RIP Routing Configuration

To configure RIP routing, just turn on the protocol with the router rip command and tell the RIP routing protocol which networks to advertise. That’s it. Understand that RIP is configured with classful routing network addresses!



RIP Version 2RIP Version 2

• Allows the use of Variable Length Subnet Masks (VLSM) by sending subnet mask information with each route update

• Distance Vector – same AD, and timers.• Easy configuration, just add the command “version 2” under

the router rip configuration• Uses Multicast address 224.0.0.9 versus broadcast like RIP

version 1• RIPv2 allows routing update authentication

router ripnetwork 10.0.0.0version 2

Easy configuration, just add the command “version 2” under the router rip configuration.RIPv2 is the preferred choice over RIPv1 because it supports VLSM and discontiguous networks.



Discontiguous AddressingDiscontiguous Addressing

• Two networks of the same classful networks are separated

by a different network address

192.168.10.16/28

10.1.1.0/24

192.168.10.32/28

– RIPv1 and IGRP do not advertise subnet masks, and therefore cannot support discontiguous subnets.

– OSPF, EIGRP, and RIPv2 can advertise subnet masks, and therefore can support discontiguous subnets.

– To fix discontiguous networking, use the no auto-summary command

If you create VLSM network, sometimes you may find that the backbone connecting buildings together is a different class of network. This is called discontiguous addressing. By default routing protocols will not work across discontiguous networks. By using the “no auto-summary” command on the network boundaries, routing protocols will be able do work across a discontiguous addressed network.



Passive InterfacePassive Interface

Maybe you don’t want to send RIP updates out your router

interface connected to the Internet. Use the passive-

interface command:

Router(config)#router rip

Router(config-router)#passive-interface serial0

This allows a router to receive route updates on an interface, but not send updates via that interface

S0 GatewayInternet

UpdatesXX

You probably don’t want your RIP network advertised everywhere on your LAN and WAN—there’s not a whole lot to be gained by advertising your RIP network to the Internet, now is there?No worries—there are a few different ways to stop unwanted RIP updates from propagating across your LANs and WANs. The easiest one is through the passive-interface command. This command prevents RIP update broadcasts from being sent out a defined interface, but that same interface can still receive RIP updates.



Verifying RIPVerifying RIP

Router#show ip protocols

Router#show protocols

Router#show ip route

Router#debug ip rip

Router#undebug all (un all)

Show ip protocols: show routing protocols information and timersShow protocols: show routed protocol informationShow ip route: displays the routing tableDebug ip rip: show rip updates being sent and received on your routerUndebug all or no debug ip rip: turns off debugging



Verifying the RIP ConfigurationVerifying the RIP Configuration

A B CE0

S3S3S2S2E0172.16.1.0

10.2.2.3

192.168.1.0

10.2.2.210.1.1.210.1.1.1

172.16.1.1 192.168.1.1

This figure shows how the show ip protocol command is used to monitor RIP operation.The command displays the routing protocols that are active on the router for IP. It also gives network and timer information.Notice the list of networks for which the router is injecting routes and lastly, notice the administrative distance metric.



Displaying the IP Routing TableDisplaying the IP Routing Table

A B CE0

S3S3S2S2E0172.16.1.0

10.2.2.3

192.168.1.0

10.2.2.210.1.1.210.1.1.1

172.16.1.1 192.168.1.1

This figure displays the show ip route command, which displays the contents of the router’s IP routing table.Notice the locations of the hop count (metric) and the administrative distance (120).

R—Refers to routes learned from RIP.via—Refers to the router that informed us about this route.00:00:07 timer value—RIP updates are every 30 seconds. Ask, “How long until the next update?”The interfaces used for the best path

Documents

CCENT - · PDF fileCCENT Course Outline Chapter 3: The Cisco Router and Switch Interface - Cisco IOS - Cisco CLI - Administrative Functions - Configuring Interfaces