牛鞭能擦进去一米多吗

牛鞭能擦进去一米多吗

Monday, August 15, 2011

Exploration 1 (Chapter 11)

                   This chapter is all about CONFIGURATION AND TESTING YOUR NETWORK, the term configuration has several meanings , in computing it may refer to: Computer configuration or system configuration , Configure (computing) is the output of Autotools and used to detect system configuration (This is referred to as "./configure" in Unix) , Configuration file is a software file used to configure the initial settings for a computer program. In Cisco configuration, the term is all about configuring computers, switches, and routers to build an Ethernet-based local area network this configuration is through the CLI interface in the packet tracer. This chapter is just an introduction of all the configuration mode of the devices need to be configured, it discusses only the basic configuration modes, other configuration modes are located in exploration 2 chapters 1,2,3,4,5, i think or most of the half of the whole exploration 2....

Router Configuration
               In this chapter we need to use the packet tracer in order to execute the configuration discussed, the main configuration is in the router, the router is a device connected to a network. The router is a computer also but it does'nt have a screen so in the real world we configure the router by mean of another computer, there's a cable must be connected to a router and computer in order to manipulate the configuration. In the packet tracer we usually configure the router directly to the router alone in his CLI interface but before configuring we need to buy first a WIC-2T  on the router that's the first thing to be done, then we will go the CLI to start configuring the router, upon configuring it has a default commands (the right term is MODES) to execute configuration, basic modes as stated below. We can configure a router in a packet tracer also like what must be done in a real world, what I mean is we will configure the router by the computer connected to it the packet tracer`, this must be done only we connect router and computer by the CONSOLE cable, then by opening the computer we can go to its terminal to configure a router, the same modes as configuring the router directly. Routers also has a Flash memory like in the computer because as what I said router also is a computer... when the configuration is done you can test the network by means of sending message to computer to router or computer to computer, if the message successfully sent it means that the configuration is successful also and the network is successfully built... Configuring and testing of the network is all done in CISCO Packet Tracer. . .


Below are some coding on Basic configuration for cisco router:

Enter Privilege Mode
Router > enable
Enter Configuration Mode
Router# configuration terminal
Password need when enter into Privilege Mode next time

Router(config)# enable password p@ssw0rd
Router(config)#enable secret s3cr3t
Configure Hostname / Router Name

Router(config)#hostname myrouter1
[Set the hostname to myrouter1]
Configure the Message of the Day(MOTD)
myrouter1(config)# banner motd # This is a secure system. Authorized access ONLY!!!. . . # 
[set a banner for welcome message] 
Configure Ethernet Port Command
myrouter1(config)# inte f0/0
[Enter Ethernet Interface Mode ( f0/0 for interface1, f0/1 for interface 2)]
myrouter1(config-if)# ip add 192.168.0.1 255.255.255.0
[Set IP address and subnet mask]
myrouter1(config-if)#no shut
[Active the port]
Configure Serial Port Command
myrouter1(config-if)#inte s 0/0/0
[Enter Serial Interface Mode]
myrouter1(config-if)#ip add 192.168.20.1 255.255.255.0
[Set IP address and subnet mask]
myrouter1(config-if)#no shut
[Active the port]
Set the Router BandwidthSet the bandwidth to 1G, Clock Rate only apply at Master Router
myrouter1(config-if)#clock rate 1000000
[Set the bandwidth to 1Gig]
myrouter1(config-if)#exit
Secure Console
myrouter1(config)#line con 0
myrouter1(config-line)#password c0ns0l3

myrouter1(config-line)#login
myrouter1(config-line)#exit
Secure Aux line– Auxiliary Password, use to connect a modem to a router for remoteconsole connection, Aux only available for old router, new router doesnot apply
myrouter1(config)#line aux0
myrouter1(config-line)#password auXo

myrouter1(config-line)#login
myrouter1(config-line)#exit
Secure VTY line – Virtual Terminal Password, Use to secure your login from telnet or ssh
myrouter1(config)#line vty 0 4
myrouter1(config-line)#password v1rtu@1
myrouter1(config-line)#login
myrouter1(config-line)#exit
myrouter1(config)#exit
Save setting
myrouter1#wr me

or
myrouter1#copy run start
Checking configuration
myrouter#show ip interface brief 
[make sure that u are in the privilege mode before checking]

The above code are just a very basicconfiguration for cisco router, there are more advance configurationneed for routing purpose such as static routes, default routes and dynamic routes. Within dynamic routes, there are also RIP Routes (Routing Information Protocol), IGRP Routes (Interior Gateway Routing Protocol)OSPF Routes (Open Shortest Path First) and EIGRP Routes (Enhanced Interior Gateway Routing Protocol), you can search all the advance configuration in the cisco exploration 2 or in the internet. . .

Sunday, August 14, 2011

Cisco Exploration 1( Chapter 10)

            The chapter 10 of Exploration 1 discusses the Planning and cabling of the network. We as human we plans for what must be done and we plan for our future, in Computer Networking side there is planning also as well as cabling in order to have a successful communication process in the network and for the future growth as well. This chapter discuss the basic computer network end devices, cables and intermediary devices/internetwork devices such as routers that connects to a different network and routes packets between the networks and  has the ability to break up broadcast domains and collision domains in order to meet the requirements to build a LAN or WAN connection.

Planning and Cabling Network   
             Choosing the appropriate LAN devices is one of the factor need to be planned to have a connection, we need to have an Internetwork devices the most two common devices are HUBS and SWITCHES. Hubs are less expensive than switches, it creates logical bus, receives signal and sends the signal over all ports. Switches are chosen for connecting devices to a LAN , it is more expensive than a hub, its enhanced performance and reliability make it cost effective, it receives a frame and regenerates each bit of the frame on to the appropriate destination port. Each port on the switch creates a separate collision domain. In selecting devices there are factors that need to be considered the Cost, the Speed and Types of Ports/Interfaces, the Expandability, the Manageability, and the Additional Features and Services. In Planning and cabling network we need to consider the work area, how big it is and where must the cable built and implemented, we need to consider the telecommunication room. Cabling distance is a significant factor in data signal performance, signal attenuation and exposure to possible interference increase with cable length. In order to have a successful connection in a network we need to determine the number of hosts by this formula ( 2 to the nth power minus 2 (2^n-2) and the subnet mask of a network and need to plan a future expansion of the network when in the future we need to expand the network in other department or other building. We also need to ensures that data communications are available at the best combination of cost and performance so that the networks work well with provisions to scale as needed and addressing schemes also facilitate easy configuration and troubleshooting.

Key Terms and Important Factors

Data Communications Equipment (DCE) - A device that supplies the clocking services to another device. Typically, this device is at the WAN access provider end of the link.
Data Terminal Equipment (DTE) - A device that receives clocking services from another device and adjusts accordingly. Typically, this device is at the WAN customer or user end of the link.

Subnet Masks - A unique subnet and subnet mask for each physical segment, a range of usable host addresses for each subnet.

Use straight-through cables for connecting:  
Switch to router , Computer to switch , Computer to hub 

Use crossover cables for connecting: 
Switch to switch , Switch to hub, Hub to hub , Router to router, Computer to computer , Computer to router

UTP INTERFACES:
MDI - media-dependent interface
MDIX - media-dependent interface, crossover

End devices requiring IP addresses include:
User Computers , Administrator Computers , Servers , Other end devices( printers, IP phones, and IP cameras)

Network devices requiring IP addresses include:
Router LAN gateway interfaces , Router WAN (serial) interfaces


Reasons for subneting:
Manage Broadcast Traffic , Similar Network Requirements , Security

Network Addressing Scheme:
Scalability , Reliability , Flexibility , Dynamic , Availability

Types of interfaces found in Cisco:
Ethernet Interface , Serial Interface, Console interface , Auxiliary (AUX) interface




*Note: I enumerate the most important term in KEYTERM AND IMPORTANT FACTORS for my benefit when time of review for the upcoming examination..
              

Saturday, August 13, 2011

CISCO Exploration 1 (chapter 9)

          The chapter 9 in cisco exploration 1 talks about the Ethernet, how it evolve , its functions, how it connects, how it communicate and how it works in the society nowadays. Upon reading the title of this chapter in Cisco exploration 1 I have some questions build in my mind like What is Ethernet? Does Ethernet and Internet the same or not? If not , how they differ to each other? so in order to answer all my question I read the chapter.

What is Ethernet?
            Ethernet is a family of computer networking technologies for local area networks (LANs) commercially introduced in 1980 by a consortium of Digital Equipment Corporation, Intel, and Xerox (DIX). It is also Standardized in Institute of Electrical and Electronics Engineers (IEEE) 802.3 which defines several wiring and signaling  and it has largely replaced competing wired LAN technologies. Systems communicating over Ethernet divide a stream of data into individual packets called frames who contains source and destination address and it has also an error-checking data so that damaged data can be detected and re-transmitted. Ethernet uses a bus or star topology and supports data transfer rates of 10 Mbps.

Functions, Evolution and Others
            Ethernet function by means of first two layers in the OSI Model which is the Physical Layer and the Data Link Layer. In Physical Layer it defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. In the data link layer it covers the two sublayers of the datalink layer the Media Access Control Sublayer and the Logical Link Control Layer. In MAC Sub layer, it works on the physical components which is useful for computer communications  and it has an  IEEE 802.3 standard.  The LLC Sublayer of the data link layer creates a connection with the upper layers and and contribute significantly to technological compatibility in the computer, it also has an IEEE 802.2 standard.  Ethernet also uses the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method to handle simultaneous demands and it is one of the most widely implemented LAN standards. Base in exploration 1 CSMA/CD is the first known Ethernet. CSMA/CD is a Media Access Control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared transmission medium, such as an electrical bus, or a band of the electromagnetic spectrum. How it works? Carrier sense has a transmitter that uses feedback from a receiver that detects a carrier wave before trying to send and it tries to detect the presence of an encoded signal from another station before attempting to transmit. If a carrier is sensed, the station waits for the transmission in progress to finish before initiating its own transmission while in Multiple Access it describes the fact that multiple stations send and receive on the medium and transmissions by one node are generally received by all other stations using the medium.

Does Ethernet and Internet the same or not? How they differ?
            This is one of the questions built in my mind when I see the word Ethernet in chapter 9 of exploration 1 before reading it as a whole that is why I searched the answer and I want to share it to everyone.

ETHERNET: LAN [local area network] - it connects your computer to computers close by and around you

INTERNET : WAN [wide area network] - basically, this is the internet as you know it. It connects your computer to computers around the world

ethernet is almost always faster than internet
and ethernet can be connected to an internet, sometimes making things confusing

just remember: ethernet = close
                       internet = worldwide

Sunday, August 7, 2011

COMS 113 -Data Communication (chapter 8)

In the previous chapters of Cisco we already tackle about the OSI Model in which the Physical Layer is the first step or the first layer of the model, we all know that it supports the electrical or mechanical interface to the physical medium. Chapter 8 is all about the Physical Layer upon reading it I found out that the chapter explains the purpose, operation, the standards and the basic characteristic of copper, fiber and wireless media of the Physical Layer and how it connects to the data networks. 
This Layer works for the communication and in order to communicate we need to have a signal to connect to network. The physical layer create electrical, optical and microwave signal that represented by the bits from data link layer and bits are encoded for transmission with NRZ (Non-Return to Zero) encoding and ManchesterEncoding, after transmission it will go to its destination. The signal will be sent to the media one at a time. The type of the signal depends on the type of media who carries the signals and it has three basic forms the copper cable media, the fiber media and the wireless media. Copper cable has electrical hazards and the signals are patterns of electrical pulses the example of its connector are RJ-45 and RJ-11. Fiber cables are not electrical conductor and the signals are pattern of Lights, it has low signal loss that can operate with much greater lengths compare to copper cable media, examples of its connectors are Straight-Tip (ST), Subscriber Connector (SC), and LucentConnector (LC). Wireless media is not restricted to conductors of pathways, as are copper and fiber media and the signals are patterns of radio transmissions, some types of wireless connections are Standard IEEE 802.11  Wi-Fi/ Wireless LAN(WLAN)), Standard IEEE 802.15(Wireless Personal Area Network(WPAN), Standard IEEE 802.16 (Worldwide Interoperabilityfor Microwave Access (WiMAX) and Global System for Mobile Communications (GSM). If we all observed the commonly used wireless connection nowadays is Wi-Fi.
 Bits are encoded as symbols to represent encoded data or control information called code group before transmission to its destination. Transferring of data can be measured in three ways: Bandwidth, Throughput and Goodput.  Bandwidth measures the amount of information that can flow one place to another in a given amount of time; Throughput is the measure of the transfer of bits across the media over a given period of time; and Goodput measure of usable data transferred over a given period of time. 

SELECTED TERMS


NRZ(Non-Return to Zero)encoding -  a "0" may be represented by one voltage level on the media during the bit time and a "1" might be represented by a different voltage on the media during the bit time.

Manchester Encoding - uses transitions, or the absence of transitions, to indicate a logic level. For example, a "0" is indicated by a high to low transition in the middle of the bit time. For a "1" there is a low to high transition in the middle of the bit time...

Code group - is a consecutive sequence of code-bits interpreted and mapped as data bit patterns.

Purpose of Physical Layer – It provides the means to transport across the network media the bits that make up a Data Link layer frame.

Operation of the Physical Layer – The media does not carry the frame as a single entity. The media carries signals, one at a time, to represent the bits that make up the frame.

Standards of Physical Layer – It consists of hardware, developed by engineers, in the form of electronic circuitry, media, and connectors. Therefore , it is appropriate that the standards governing this hardware are defined by the relevant electrical and communications engineering organizations.