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Audio training is perfect anywhere, especially during your long commute to work or school. Click the link above called "Download the accompanying reference guide. I really enjoy the audio, lecture series. The lectures reference these diagrams a few times, they are referenced in a way that you need the resource material diagrams to follow along.
Granted if you are driving and listening you cannot follow diagrams, but you could review the diagrams that spark interest and re-play audio portion again. The clear voice of the narrator as well has his way of explaining the material. What did you like best about this story? I liked that it went over a lot of sub-topics in a reasonably short amount of time without confusing you with unneeded information. Any additional comments? For the people talking about not being able to find the reference It's there, open your eyes.
Also, to the guy talking about how it's not good for listening to in the car because of not being able to use the reference guide. I agree with you, but when I bought this audio book I knew fair well before hand that I would not be listening to it in the car.
Unlike many other audio books, this one is definitely more of a sit at your computer while looking at the reference guide type of audio book. TLDR: There is a link to the reference guide on the same page that you purchased the book from the product page Also, this is much more efficient listening to at home with the reference guide in front of you, not while out and about.
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Books in this series provide officially developed self-study solutions to help networking professionals understand technology implementations and prepare for the Cisco Career Certifications examinations. This book provides you with the knowledge needed to configure Cisco switches and routers to operate in corporate internetworks. By reading this book, you will gain a thorough understanding of concepts and configuration procedures required to build a multiswitch, multirouter, and multigroup internetwork that uses LAN and WAN interfaces for the most commonly used routing and routed protocols.
Many notes, tips, and cautions are also spread throughout the book. For example, You cannot assign this address to any network device. Private addresses are functionally the same as public IP addresses addresses that operate on the Internet ; however, every Internet Service Provider ISP that allows you to connect to the Internet blocks private addresses from reaching the Internet. This allows an organization to have a full network infrastructure between all of their offices without any fear of users in their organization reaching the Internet or anyone on the Internet reaching users in the organization.
Home Office They are as follows: n. Class A: These addresses will function on internal networks, but will not function on the Internet. As a sneak peek of technology to come later in this guide, most organizations will use Network Address Translation NAT to allow their users to access the Internet despite the use of private addresses on the internal network. Common IP Services When building a network infrastructure, you will need to assign the devices on the network IP addresses from the appropriate network ranges.
This can be done either statically or dynamically. In Microsoft Windows XP, you can statically assign an address by opening the Control Panel, double-clicking Network Connections, right-clicking the network adapter you would like to configure and selecting Properties.
In Microsoft Vista, you can statically assign an address by opening the Control Panel, doubleclicking Network and Sharing Center, clicking on Network Connections on the left, right-clicking on the network adapter you would like to configure and selecting Properties. While statically assigning addresses is absolutely necessary for key network devices such as servers, printers and routers, it can become quite tedious and unmanageable for hundreds, if not thousands, of individual PCs.
Once that is created, the administrator no longer needs to statically assign IP addresses to each network client. The process of DHCP can be depicted as follows on the page below:. For example, it is much easier to remember www.
Client These DNS server lookups occur anytime a client is attempting to access anything using a common name rather than an IP address. Ready to pass the CCNA exam? Download a free practice exam preview to find out if youre ready to pass.
Common Client Tools While much of the Cisco configuration work involves interacting with routers and switches in the IOS, the majority of your troubleshooting will be done from a network client.
Because of this, it is absolutely critical that you understand a few of the common command line test tools. To run this utility, simply open a command line and type ipconfig. By typing this simple command shown on the next page , you will be given the IP address, subnet mask and default gateway assigned to the PC. For example, after a client resolves www. If the IP address of Google changes during that time, it may be necessary to manually flush the cached DNS entries on a client.
If there were a flathead screwdriver in the network world, the ping command would be it. The ping command tests network connectivity to a remote device.
Technically, it puts the entire alphabet a through z in a packet and sends that packet to whatever device you specify. When the device receives it, it sends it right back. You can then measure the time it took to reach the remote device. The following is an example of a ping to www. As you can see, the Microsoft Windows PC will send four ping requests to the destination by default and display the response time in milliseconds for each attempt.
There are three common arguments used with the ping command: n. For example, issuing the command ping a You can increase the size by using the l argument that is a lowercase L not a 1. For example, you could type ping l www. This is useful when stress-testing connections or servers. The traceroute command implemented as tracert in Microsoft Windows is an enhanced version of a ping that shows every router you are passing through on the way to your destination.
As you can see, the tracert command sends three ping requests to each router that it passes through. This allows you to find the bottleneck between the source and the destination. In the example above, There is only one common argument for the tracert command: n.
For example, ip This speeds up the traceroute command considerably. The nslookup command allows you to send multiple queries to a DNS server. There are many cases in network troubleshooting where problems originate because a DNS server has incorrect name-to-IP-address mappings in its database.
Nslookup can help diagnose these issues. The following is an example of using nslookup to query a local DNS server:. When you enter a domain name to resolve, nslookup will provide the name and IP address of the DNS server resolving the name adtec.
This is because Google has a large enough web presence to have redundant servers supporting its domain name. There are many options that can be used with the nslookup command; two of them have common relevance to Cisco technicians.
Keep in mind that both of these commands are entered after you have entered the base nslookup command: n. For example, in the nslookup output above, I was using the server adtec. Perhaps I suspected that the adtec server was returning incorrect information.
Using the server command, I could redirect my DNS requests to a different server. Tip: the DNS server 4.
For example, google. Typing ls google. Please keep in mind that many DNS servers restrict this command because of the secure information it can display. Whenever a network device attempts to communicate, it will need to have both the Layer 3 IP address and Layer 2 MAC address of its destination. For example, if the network client Using the arp command-line utility, you are able to verify these mappings as shown below:.
In the example above, the IP address The arp command is unique in that you cannot issue the command without any arguments. The following are common arguments for use with the arp command: n. This command is demonstrated in the previous graphic.
In a network where IP addresses are changing usually due to network maintenance or upgrades , it may be beneficial to flush the arp cache and allow it to dynamically rebuild.
The following list will provide the hard-facts for both protocols. Connectionless: Does not notify receiving device that information is about to be sent; the UDP application just sends information and assumes it is received. Limited Error Checking: UDP can optionally include a header checksum, which can be used to test if header corruption occurred when the message was sent. No Sequencing: UDP does not have the ability to tell what order packets were sent in. Therefore, any data received out of order may be dropped by the receiving device.
Connection Oriented: Before any data is sent, an active session connection is set up between network devices. Error Checking: TCP always includes a header checksum, which can be used to test if any header corruption occurred when the message was sent. Data Recovery: After the initial session is created between two network devices, all transmissions are acknowledged ACKed to ensure data is not lost.
If a message is not acknowledged, it will be retransmitted. TCP uses sequence numbers on all transmitted data to ensure it is able to be placed in the correct order. Because of its reliability, TCP is by far the most popular protocol for day-to-day application such as web browsing, email and file transfers. As seen before in our OSI Model discussion, the communication will come from a source port, which designates the client application it came from, and will be directed to a destination port, which designates the server application it would like to access.
All four packets are sent without warning and without expecting any acknowledgement. The foundation that TCP communication relies on is in building a session. Its very similar to when you first meet someone. You dont run at them initially spewing information data ; instead, you take the time to introduce yourself and find out the identity of this new person. In the figure below, the TCP client In the initial packet, the client uses two TCP header fields to relay some key information.
The first is the Control CTL field. In this case, it is a Synchronization SYN message, letting the remote server know the client is beginning communication. As data is sent, this sequence number will continue to increase to ensure the data remains in order.
This initial packet is telling the server the starting sequence number for the client. In this case its Now lets see how the server responds:.
Since the server is a completely different device than the client, it will have its own starting sequence numbers for communication.
In this case, it will begin by starting with SEQ You can also notice a new field in the packet, which is the acknowledgement ACK number.
Notice that it is , one more than the TCP clients sequence number. The ACK numbers should always be one more than the last sequence number unless data was lost during transmission. Once this third packet is received by the TCP server, the session is built and data can be sent. When the server acknowledges receipt of the data, it will reply with ACK number If the client has 1,, bytes 1 Megabyte of data to send, sending one byte of data at a time is an extremely inefficient process to accomplish this.
Think of it as having a conversation with a person, but you can only say one word at a time and must wait for each word to be acknowledged before saying another word.
To help with this issue, the idea of TCP windowing was introduced. As the devices detect a more reliable connection, the amount they send known as the window size increases. The figure below demonstrates this concept. Rather than start by sending a single byte of data, most operating systems will begin somewhere around bytes of data.
Each time a successful acknowledgement comes back, the sending PC increases its window size by a factor of two, sending , then , then bytes of data. Again, the amount the window size increases is dependent on the operating system, but doubling the window size each time is typical.
This process will continue until the sending computer loses some data during the transmission due to the receiving computer or some network device between the sender and receiver not being able to keep up or until the receiving computer communicates back that its maximum TCP window size has been reached.
So, for the final transmission, the PC is most likely sending multiple packets for each acknowledgement received. IP: Router User IP: If you have ever copied a large file to a server, you may have seen the idea of TCP sliding windows in effect.
Initially, the amount of time to copy the file is reported as some astronomically large amount, such as 15 hours. As you let a few seconds pass, you notice that the time has decreased dramatically to 4 or 5 hours. After a few more seconds, the copy time estimate has decreased to 2 to 3 hours. You are seeing the effect of TCP sliding windows before your very eyes. As the window size becomes greater, the transmissions become more efficient and the time to copy the data becomes significantly less.
End-to-End Network Communication After seeing all of these concepts, you may find it helpful to see a complete example of end-to-end network communication between two devices.
For this example, we will use the following network diagram: The user shown on the left of the diagram has opened a web browser to access the web server on the right. The following describes the general process of communication: Phase 1: Initial Network Communication n. The web browser passes the request down to the operating system.
Based on the application being used, the operating system realizes this will be TCP-based communication. In order to direct the data to the correct application, the operating system tags the packet with the destination port number of 80 the well-known port number for HTTP.
To allow return traffic to the client, the operating system dynamically assigns port 53, to the web browser application as the source port number. The users PC is able to determine that the remote web server is on a different network.
The router receives the frame and checks the destination MAC address. Since the router sees The router looks at its routing table and sees it is attached to the Before it can send the data to the web server, it must replace these addresses with MAC address information relevant to the web servers network.
Since the web server sees As the web server processes the Transport layer information, it realizes this is a TCP SYN packet, which indicates a host is attempting to begin network communication.
The web server realizes the destination IP address is not on its network and adds its own source MAC address f3:cc33 and the destination MAC address of the router 00a9:ffca. The frame is sent to the router. Before it can return the data to the user, it must replace these addresses with MAC address information relevant to the users network. The router adds its own MAC address as the source 00a and the users MAC address bcb51 as the destination. The frame is sent to the users PC.
This initial introduction is designed to hit the high-points of Ethernet networking. So, lets work through Ethernet, starting with the Physical layer aspects. This physical cabling standard specifies eight individual wires that are twisted together into a cable and crimped using an RJ tip. Simply put, Cisco wants to know, Do you know which Ethernet cable to use?
This decision comes down to a choice between Ethernet Straight-Through and Ethernet Crossover cabling. In the LAN environment, there are devices that are designed to naturally connect. For example, a server, PC or router will typically plug directly into a network switch or hub.
Because the devices are engineered to connect this way, the network plugs are designed physically differently. A PC will send data on pins 1 and 2 of the Ethernet cable known as Tx pins. A switch or hub is designed to receive data on pins 1 and 2. Likewise, a PC is designed to receive data on pins 3 and 6 known as the Rx pins , and a switch or hub is designed to send data on these pins.
Whenever you are making these natural connections, you are able to use an Ethernet straight-through cable. An easy way to remember this is that it is used when you are connecting unlike devices. Some examples of these include: n. While these connections are the most common in LAN environments, you will also run into cases where you have a need to connect like devices. If you attempt to do this using an Ethernet straight-through cable, the devices will not be able to communicate since they are wired to send and receive on the same pins.
It would be synonymous to two individuals attempting to speak without listening or listen without speaking. Ethernet: The Data Link Layer Physically connecting devices using the correct cables is just a small portion of Ethernet communication. The connected devices must now understand what they are saying, which is the job of the Ethernet Data Link layer: correctly formatting electrical signals so they are understandable by each end.
To accomplish this, the Ethernet layer is divided into two, smaller sub-layers: n. Since the functions of the LLC sub-layer are simpler, lets discuss those first. Without this layer, Ethernet would be tied to a specific Network layer protocol that could never change unless the whole Ethernet standard was changed. The MAC sub-layer is primarily responsible for error correction and addressing functions.
The error correction comes in through a small check known as the Frame Check Sequence FCS , which is added on at the end of the frame:. The FCS is the result of a mathematical formula run on the entire frame.
This is technically known as a hash. When a PC decides to send data across the network, just before it is sent, it runs a mathematical formula on the entire frame and puts the result of this formula the hash in the FCS field at the end. When the data is received, the first thing the receiving device does is to run the same formula on the data and compare the result to the result contained in the FCS. If the results match, the frame is considered good and will be processed.
If the results do not match, it means the data in the frame must have become corrupted or maliciously modified by a network intruder. The frame is considered damaged and will be dropped. The second major function of the MAC sub-layer is addressing. In the Network Foundations section, we discussed the concept behind the MAC address but never looked specifically at its format.
The Ethernet MAC address is 6-bytes long and can be written in a variety of formats, depending on the type of equipment you are working with. The following are examples of the same MAC address written different ways: n. This can sometimes throw off network technicians who are used to the rigidity of the format of an IP address. Each MAC address uniquely identifies each network card in the world. With 6-bytes of data bits , it is possible to have or ,,,, possible MAC addresses.
The OUI is assigned to organizations producing network equipment. For example, if Intel decided to create a new network card, they would apply for an OUI which is assigned to the Intel organization. If Intel were assigned b as their OUI, they would begin creating network cards starting with this OUI as the MAC address for example, b, b, and so on.
This standard defines the rules Ethernet must live by when communicating. Based on the Ethernet standard, only one device connected to an Ethernet segment is able to send or receive at a time, otherwise a collision occurs and the data must be re-sent.
Send the network device packages data into a frame to be sent. The network device listens to the Ethernet wire to see if another device is already transmitting. If a device is transmitting, wait until it finishes. If the line is idle, send the data. This system works flawlessly unless two network devices happen to be listening to the Ethernet wire at the same time. The more devices you add to the network, the chances of this happening increase.
Collision is detected by the sending network devices. A jam signal is transmitted on the Ethernet wire. This signal causes all devices to stop sending. The sending devices set a random retransmit time and send the data again, hoping not to collide. If another collision is detected, the random retransmission timer is continually increased until the data can be sent without colliding.
Ethernet Network Equipment From the network client side, anything with an Ethernet-capable NIC is obviously part of the Ethernet network equipment realm; however, as Cisco engineers, were mostly interested in the network infrastructure realm. In this realm, there are two network devices of concern: the hub and the switch. To have a complete appreciation for these devices, you must understand the concept of collision domains.
Understanding Collision Domains A collision domain represents a shared Ethernet segment where only one device can send or receive at a time. Hubs, which are older network equipment, can only support a single collision domain. This means that no matter how many ports a hub has or how many hubs are connected using crossover cables, there will only be a single collision domain:.
This brings us to the major difference between hubs and switches. A network switch isolates each port into its own collision domain:.
A switch-based network allows a network to be tremendously more efficient than a hub-based environment. As I just mentioned, switches provide the capability of full-duplex. This allows a network device to send and receive at the same time rather than half-duplex, which allows a network device to send or receive at the same time.
All network equipment is rated as if it were running at half-duplex, so when you use a Mbps NIC, you can actually achieve Mbps of throughput if operating in full-duplex Mbps sending and Mbps receiving at the same time.
Hubs and Switches, Exposed In addition to multiple collision domains, switches offer additional benefits over hubs: n. Dedicated Bandwidth Since each host is isolated into their own network segment collision domain , they are dedicated the full amount of bandwidth the switch port can provide.
If you have a Mbps switch, each attached port will receive a full Mbps of bandwidth. If you have a Mbps hub, the bandwidth is divided among the devices needing to transmit data. If four devices have data to send, the bandwidth of the hub would be divided between them. By building a MAC address table in memory, it can then direct messages out specific ports. For example, if HostA wanted to send data to HostB, the switch could allow the data to only reach HostB rather than sending it to all attached devices.
When using hubs which is a Physical layer device , every message is sent out of all ports regardless of the destination. Speed Mismatches Since each of the ports are handled individually, switches are able to handle variable speed ports. For example, you can have a port switch equipped with 22 1Gbps ports and two Gbps ports. Hubs must have all ports set to equal bandwidth amounts. When a switch initially boots, its MAC address table is completely empty. As network devices transmit data, the switch becomes more intelligent.
This process is shown below:. HostA sends data to HostB. Because the switch does not know the location of HostB, it floods the message from HostA out all ports except the port where the message was received. HostB sends data back to HostA on Port 3. Since the switch knows the location of HostA, the information is only forwarded out Port 1. HostC and HostD do not receive the information. Learning the operation of this command-line interface is critical to your survival in the Cisco realm.
Cisco has designed this command-line interface to be easy to use and navigate once you have learned the foundations. This section is focused on just that: learning the foundations of working with the Cisco IOS. Think of this as being similar to getting a training course on how to work with Microsoft Windows.
In the Windows realm, we would look at things such as learning to use the mouse, the Start menu and the Control Panel.
In this introductory training, we will focus not so much on how to perform configurations but, rather, just how to get around. Connecting to the Cisco Switch or Router When you pull a Cisco switch or router out of the box, it will have little or no configuration. In order to connect to the Cisco switch or router, we must use a specialized Console cable. This type of cable is also known as a rollover cable since the eight Ethernet pins roll over between the ends. On one end of the console cable, you will need a DB-9 serial port adapter, which connects to the PC.
Many of the newer Cisco console cables have these serial adapters built-in:. After you have connected one end of the console cable to your PC and the other end to the Cisco switch or router, you will need a terminal emulator program to interact with the Cisco router.
The following is a list of common terminal emulators: n. Once you have opened one of these programs, you will need to select your PC COM port for the connection. Once you have configured these settings, you can click OK and press the Enter key a few times in the terminal program. A prompt from the Cisco device should appear. Understanding the Cisco IOS Modes When working with the Cisco IOS, understanding the relevance of the mode you are in is almost as important as understanding the command you should type.
There are hundreds of different modes, each of which allows you to configure a different aspect of a Cisco device. The modes are always accessed through this general flow:. From User Mode, you have extremely limited access to view information such as interface status, router uptime and IOS version information. Commands that could expose any security-related information are disabled in this mode. Privileged Mode This mode allows you to view the full configuration of the Cisco IOS device and provides access to troubleshooting and testing utilities such as the debug commands.
This is the only mode which allows you to save your IOS configuration. Some examples of these settings are the name of the IOS device, a logon banner and the privileged mode password. More importantly, from global configuration mode, you can access any of the sub-configuration modes. These modes give you an interface to configure specific aspects of the router or switch.
For example, you could configure an individual interface by moving into Interface configuration mode. The IOS prompt always consists of two pieces: the hostname of the device and the mode you are currently accessing. The following is an example of what each of the modes look like: n.
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