Chapter 11 Configuring and Testing Your Network

In this chapter they use the Cisco Internetwork Operating System to interconnect and configure the computers, switches, routers into an Ethernet LAN. The Cisco IOS services are generally accessed using a command line interface (CLI). T here is several ways to access the CLI environment. The most usual methods are: Console; Telnet or SSH; and AUX port. When the networking services have not been started or have failed, the console port is frequently used to contact a device.

Samples of console use are:

·         The initial configuration of the network device

·         Disaster recovery procedures and troubleshooting where remote access is not possible

·         Password recovery procedures

Telnet session needs dynamic networking services on the device. Another way for remotely accessing a CLI session is to telnet to the router. The Secure Shell (SSH) protocol is a more safe way for remote device access. This protocol gives the composition for a distant login similar to Telnet, but it utilizes safer network services.

Other way to establish a CLI session distantly is using a telephone dialup connection using a modem connected to the router's AUX port. The same as to the console connection, this other way doesn’t involve any networking services to be configured or existing on the device.

Startup Configuration File (startup-config) is used at some point in system startup to organize the device. The startup configuration file or startup-config file is stored in non-volatile RAM (NVRAM).

Running Configuration - Changes to the running configuration will directly influence the function of the Cisco device.     

Router(config)# - the default prompt for the global configuration mode on a router

The two primary modes of operation are:

User EXEC- this is useful for some basic operations but still it has limited capabilities. That’s why it only allows a limited number of basic monitoring commands.

               

The user EXEC mode is identified by the CLI prompt that ends with the > symbol.

SAMPLE:              Switch> -

Privileged EXEC – Its mode can be identified by the prompt ending with the # symbol

-          It doesn’t require authentication. But still a good practice to guarantee that the authentication is configured.

SAMPLE:              Switch# -).

Enable mode – This is the term used to represent the privileged exec mode.

disable command -  This is used to exit in the privileged EXEC mode and to the return in user EXEC mode.

The basic IOS command is first the prompt, then the command, space and lastly the argument or keyword.

Commands are used to execute an action, and the

Keywords are used to classify where or how to complete the command.

Summary of IOS features and commands:

User EXEC Mode

enable - Enter Privileged EXEC mode

Privileged EXEC Mode

copy running-config startup-config - Copy the active configuration to NVRAM.

copy startup-config running-config - Copy the configuration in NVRAM to RAM.

erase startup-configuration - Erase the configuration located in NVRAM.

ping ip_address - Ping to that address.

traceroute ip_address - Trace each hop to that address.

show interfaces - Display statistics for all interfaces on a device.

show clock - Show the time set in the router.

show version - Display currently loaded IOS version, hardware, and device information.

show arp - Display the ARP table of the device.

show startup-config - Display the saved configuration located in NVRAM.

show running-config - Display the contents of the currently running configuration file.

show ip interface - Display IP statistics for interface(s) on a router.

configure terminal - Enter terminal configuration mode.

Terminal Configuration Mode

hostname hostname - Assign a host name to device.

enable password password - Set an unencrypted enable password.

enable secret password - Set a strongly encrypted enable password.

service password-encryption - Encrypt display of all passwords except secret.

banner motd# message # - Sets a message-of-the-day banner.

line console 0 - Enter console line configuration mode.

line vty 0 4 - Enter virtual terminal (Telnet) line configuration mode.

interface Interface_name - Enter interface configuration mode.

Line Configuration Mode

login - Enable password checking at login.

password password - Set line password.

Interface Configuration Mode

ip address ip_address netmask - Set interface IP address and subnet mask.

description description - Set interface description.

clock rate value - Set clock rate for DCE device.

no shutdown - Set interface to up.

shutdown - Administratively set interface to down.

Chapter 9 - Ethernet

Ethernet is a new largest LAN technology uses today. The first foundation of the Ethernet has begun on 1970 with a program Alohanet. Alohanet was a digital radio network designed to transmit information over a shared radio frequency between the Hawaiian Islands. There first attempt was to use thick coaxial cables, directly connected in a backbone and can cover only 500 meters. But still, the Ethernet was designed to accommodate multiple computers that were interconnected on a shared bus topology. Because of LANs grew larger and  increasing demands , the thick coaxial cables are replaced by a UTP cables which are less expensive, easy to use and lightweight. And its physical topology was replaced by a hub. And recently today, the hubs are replaced a switch because switches can control the flow of data by isolating each port and sending a frame only to its proper destination (if the destination is known), rather than send every frame to every device, and later it called full duplex communication. While the hub shared a media, it means it can successfully transmit only one station at a time, this type of connection is called half duplex communication. The switch has enabled the development of 1Gbps Ethernet and beyond. Because of its increasing demand the Ethernet beyond the LAN has fully developed.

                In 1985, the Institute of Electrical and Electronics Engineers (IEEE) standards committee for Local and Metropolitan Networks published standards for LANs. The standard for Ethernet is 802.3 in the layer 1 and layer 2 of the Ethernet it is used. In the Data Link layer (which is known as Media Access Control sublayer) and the Physical layer this are the two layers of the OSI model which the Ethernet operates. At Ethernet Layer 1 involves signals, bit streams that travel on the media, physical components that put signals on media, and various topologies. Ethernet Layer 1 performs a key role in the communication that takes place between devices, but each of its functions has limitations. At Ethernet Layer 2 addresses limitations. The MAC sublayer is concerned with the physical components that will be used to communicate the information and prepares the data for transmission over the media. Media Access Control (MAC) is implemented by hardware, it is in the computer Network Interface Card (NIC).The Ethernet MAC sublayer has two primary responsibilities: Data Encapsulation and Media Access Control. In the data encapsulation this provides three primary functions: Frame delimiting; Addressing; and Error detection. In MAC sublayer controls the placement of frames on the media and the removal of frames from the media. This includes the initiation of frame transmission and recovery from transmission failure due to collisions. MAC addressing is a part of a Layer 2 PDU. An Ethernet MAC address is a 48-bit binary value expressed as 12 hexadecimal digits.

                In Ethernet, different MAC addresses are used for Layer 2 unicast, multicast, and broadcast communications. In a unicast MAC address is the unique address used when a frame is sent from a single transmitting device to single destination device. In a broadcast the packet contains a destination IP address that has all ones (1s) in the host portion. The multicast represent a group of addresses (sometimes called a host group), they can only be used as the destination of a packet. The source will always have a unicast address.

                Using hubs in an extended star it can create large collision domains. Collision domain is a network segment where if one particular device sends a frame on a network segment, every other device on that same segment will process that frame. This also means that if two or more devices on that same segment transmit a frame at the same time there will be a collision. Importantly, only one device in the entire network can send data at any one time.

The Ethernet LAN switches use five basic operations:

Learning - the switch needs the source MAC address from the frame received on a port and stores it in the MAC address table for use in the forwarding of frames to host.

Aging - The entries in the MAC table acquired by the Learning process are time stamped. This timestamp is used as a means for removing old entries in the MAC table.

Flooding – The sending of frames through all outgoing ports.

Selective forwarding - is the process of examining a frame's destination MAC address and forwarding it out the appropriate port.

Filtering – a frame that is not forwarded.

The ARP protocol provides two basic functions: Resolving IPv4 addresses to MAC addresses and Maintaining a cache of mappings. Ethernet uses the Address Resolution Protocol to determine the MAC addresses of destinations and map them against known Network layer addresses.

Chapter 10 - Planning and Cabling Networks

In this chapter we must know how to identify and connect the cables to make a successful LAN and WAN connections. Router is an example of an intermediary device, a device that connects directly to the end user or provides the end user routing to other networks. In choosing in an appropriate LAN device in the Internetwork devices, the UTP cable is the one to connect the router’s LAN interfaces to the LAN media but modules can be added for using fiber-optics but also it depends on the series or model of router. In the intranetworking devices there are two most common devices used which are hubs and switches. A hub is a piece of equipment that acts as a multiport repeater. This is typically chosen to a very small LAN connection and less expensive than the switch. The switch is expensive than the hub because of its enhanced performance and reliability that cause of its cost. But before you decide in selecting a device you must have meet this factors: Cost; Speed and Types of Ports/Interfaces; Expandability; Manageability; and Additional Features and Services. The switch is more efficient than a hub but a redundant system is one of the goals in the switch because it allows the physical network to continue its operation even if one device fails. In a router this are the advantages: Expandability; Media; and Operating System Features. Its expandability comes to both fixed and modular physical configurations. Its operating system features are: Security; Quality of Service (QoS); Voice over IP (VoIP); Routing multiple Layer 3 protocols; and Special services such as Network Address Translation (NAT) and Dynamic Host Configuration Protocol (DHCP).

In planning the installation of LAN cabling, there are four physical areas to consider: Work area; Telecommunications room, also known as the distribution facility; Backbone cabling, also known as vertical cabling; and Distribution cabling, also known as horizontal cabling.

In selecting a type of media to the LAN and WAN connections there are advantages and disadvantages to be consider. This are:

 Cable length - Does the cable need to span across a room or from building to building?

Cost - Does the budget allow for using a more expensive media type?

Bandwidth - Does the technology used with the media provide adequate bandwidth?

Ease of installation - Does the implementation team have the ability to install the cable or is a vendor required?

Susceptible to EMI/RFI - Is the local environment going to interfere with the signal?

In making a LAN connection you will use a RJ-45 connector which is the male component crimped on the end of the cable. If you want to connect different types of devices use a straight-through cable and when connecting the same type of device, use a crossover cable. In short these are the devices in connecting a straight-through cable and cross-over cable:

In a straight-through cable: Switch to router; Computer to switch; and Computer to hub

In a crossover cables: Switch to switch; Switch to hub; Hub to hub; Router to router; Computer to computer; and Computer to router

In making WAN connection you will consider the chart, the serial and the DSL.

In designing an Internetwork Address Standard this are the hosts: the general users; special users; network resources; router LAN interfaces; management access; and Router WAN Links.

In WAN Interfaces the serial used for connecting WAN devices to the CSU/DSU is the Serial WAN interfaces. A CSU/DSU is a device used to make the physical connection between data networks and WAN provider's circuits. In the LAN interfaces the Ethernet is used for connecting cables that terminate with LAN devices such as computers and switches. This interface can also be used to connect routers to each other. The console interface is the primary interface for initial configuration of a Cisco router or switch. The Auxiliary (AUX) Interface is used for remote management of the router. A modem is connected to the AUX interface for dial-in access.

The device management connection needs an:

PCs require an RJ-45 to D-9 or RJ-45 to DB-25 adapter.

COM port settings are 9.600 bps, 8 data bits, no parity, 1 stop bit, no flow control.

This provides out-of-board console access.

AUX switch port may be used for a modem-connected console.

Chapter 8 - Physical Layer

What is an OSI Physical layer? It’s the layer 1 in the OSI model. Physical layer is the one who transmit binary data over media between devices. Physical layer protocols define media specification. In other words, the OSI Physical layer provides the means to transport across the media the bits that make up a Data Link layer frame. When this layer accepts the complete frame from the Data Link layer, then this layer encodes it as a series of signals that are transmitted onto the local media. And there are three basic forms of network media on which the bits are represent depend on the type of media. These are the copper cable which the signals are patterns of electrical pulses; the fiber which the signals are patterns of light; the wireless media which the signals are patterns of radio transmissions.

                There are appropriate standards in this layer that governing the hardware that relevant electrical pulses electrical and communications engineering organizations. The TCP/IP standards are set by the Internet Engineering Task Force (IETF) in RFCs. The technologies of this layer are defined by these organizations: International Organization for Standardization (ISO), Institute of Electrical and Electronics Engineers (IEEE), American National Standards Institute (ANSI), International Telecommunication Union (ITU), Electronics Industry Alliance/Telecommunications Industry Association (EIA/TIA), and the National telecommunications authorities such as the Federal Communication Commission (FCC) in the USA. These organizations defined that this layer standards are: Physical and electrical properties of the media; mechanical properties (materials, dimensions, pinouts) of the connectors; bit representation by the signals (encoding); and definition of control information signals.

                The three fundamental functions of the Physical layer are: the physical components; data encoding; and signaling.

The physical elements are the electronic hardware devices, media and connectors that transmit and carry the signals to represent the bits.

The encoding function is to convert a stream of data bits into a predefined code. The Manchester Encoding is a sample even though it represents bits as voltage transition and not efficient enough to be used at higher signaling speeds, it is the signaling method employed by 10BaseT Ethernet.

The signaling is when the physical layer generates the electrical, optical, or wireless signals that represent the "1" and "0" on the media. The signaling method can be amplitude, frequency, or phase. The NRZ signaling is a simple signaling method, its bit stream are transmitted into a series of voltage.

                In calculating the data transfer. These are the three ways: Bandwidth which is typically measured in kilobits per second (kbps) or megabits per second (Mbps); Throughput is the measure of the transfer of bits across the media over a given period of time; Goodput is the measure of usable data transferred over a given period of time, and is therefore the measure that is of most interest to network users.

The physical media or the connecting communication are the copper media, the unshielded twist pair(UTP), the coaxial cable, the other copper media, the fiber media,the wireless media and the media connectors.