Ccna command quick reference cisco networking academy program pdf

For purposes of this example, select the. Therefore, you are left with: 10N where: 10 represents the original pattern of subnetting. N represents the extra bit. This is the basis of VLSM. Each of these sub-subnets will have a new subnet mask. The mask now equals: You want to make sure the addresses are not overlapping with each other. So go back to the original table. You now have a choice as to where to put these networks.

But you only need 4 H bits, not 5. Therefore you are left with: N where: 10 represents the original pattern of subnetting. N represents the extra bit you have. Each sub-subnet now has 4 N bits and 4 H bits, so their new masks will be: Now all you need to do is determine the network numbers for the serial links between the routers.

Step 5 Determine Network Numbers for Serial Links Serial links between routers all have the same property in that they only need two addresses in a network—one for each router interface. You have two of the original subnets left to work with.

Therefore, you are left with: 00NNNN00 where: 00 represents the original pattern of subnetting. NNNN represents the extra bits you have. This is the power of VLSM! Remember that for every route you advertise, the size of your update grows. It has been said that if there were no route summarization, the Internet backbone would have collapsed from the sheer size of its own routing tables back in !

Routing updates, whether done with a distance vector or link-state protocol, grow with the number of routes you need to advertise. The more routes you have to advertise, the bigger the packet. The bigger the packet, the more bandwidth the update takes, reducing the bandwidth available to transfer data.

But with route summarization, you can advertise many routes with only one line in an update packet. This reduces the size of the update, allowing you more bandwidth for data transfer. The larger the routing tables, the longer this takes, leading to more used router CPU cycles to perform the lookup. NOTE: This example is a very simplified explanation of how routers send updates to each other.

This book has been around for many years and is considered by most to be the authority on how the different routing protocols work. Example for Understanding Route Summarization Refer to Figure to assist you as you go through the following explanation of an example of route summarization.

Without route summarization, Vancouver would have to advertise 16 networks to Seattle. You want to use route summarization to reduce the burden on this upstream router. What you are looking for are common bits on the network side of the addresses. You are left with the summarized address of By sending one route to Vancouver with this supernetted subnet mask, you have advertised four routes in one line, instead of using four lines.

The summarized route is therefore: You continue in the same format as before. Take the routes that Winnipeg, Calgary and Edmonton sent to Vancouver and look for common bit patterns: Figure shows what the routing updates would look like with route summarization taking place. Route summarization can help insulate upstream neighbors from these problems.

Consider router Edmonton from Figure Suppose that network Without route summarization, Edmonton would advertise Vancouver to remove that network. Vancouver would forward that same message upstream to Calgary, Winnipeg, Seattle, and so on. Now assume the network comes back online a few seconds later. Edmonton would have to send another update informing Vancouver of the change. Each time a change needs to be advertised the router must use CPU resources. Route summarization enables you to avoid this problem.

Even though Edmonton would still have to deal with the route constantly going up and down, no one else would notice. Edmonton advertises a single summarized route, Even though one of the networks is going up and down, this does not invalidate the route to the other networks that were summarized.

It does us no good if Winnipeg has network No summarization could take place from the edge routers to Vancouver. TIP: Because most networks use NAT and the 10 network internally, it is important when creating your network design that you assign network subnets in a way that they can be easily summarized. A little more planning now can save you a lot of grief later. Figure shows the newer smart serial end of a serial cable that connects to a smart serial port on your router.

Figure shows examples of the male data terminal equipment DTE and the female data communications equipment DCE ends that are on the other side of a serial or smart serial cable. Laptops released in the past few years come equipped with USB ports, not serial ports. For these newer laptops, you need a USB-to-serial connector, as illustrated in Figure Table describes which cable should be used when wiring your devices together.

It is important to ensure you have proper cabling; otherwise, you might be giving yourself problems before you even get started. Which Cable to Use? Although B is newer, and is the recommended standard, either one can be used.

The difference between these two standards is pin assignments, not in the use of the different colors. In both A and USOC standards, the blue and orange pairs are now on the center four pins; therefore, the colors match more closely with A than with the B standard.

So which one is preferred? Information here from the standards bodies on this matter is sketchy at best. However, A is now becoming more dominant in the USA as well. A straight-through cable is one with both ends using the same standard A or B. A crossover cable is one that has A on one end, and B on the other end.

Although these are great to use in the real world, when it comes time to write a vendor exam, make sure you know the full commands, and not just the shortcuts. Lists all commands available in the current command mode c? Router c Lists all the possible choices that start with c clear clock cl? Router c Shows all subcommands for this command. NOTE: Setup mode cannot be used to configure an entire router.

It does only the basics. You can assign an IP address to an interface, but not a subinterface. All in all, setup mode is very limiting.

Entering setup mode is not a recommended practice. Instead, you should use the command-line interface CLI , which is more powerful: Would you like to enter the initial configuration dialog?

If you say yes, you will have to wait for a few minutes while it looks for a configuration to load. Very frustrating. Say no. Be careful when you set the size to something larger than the default. By telling the router to keep the last commands in a buffer, you are taking memory away from other parts of the router.

What would you rather have: a router that remembers what you last typed in, or a router that routes as efficiently as possible?

Not all commands work in all modes. Be careful. If you type in a command that you know is correct—show run, for example—and you get an error, make sure that you are in the correct mode. This Router config prompt indicates that you can start making changes Configuring a Router Name This command works on both routers and switches. For this reason, recommended practice is that you never use the enable password. Use only the enable secret password in a router configuration.

Doing so defeats the use of encryption. Password Encryption service password- Router config s Applies a weak encryption to encryption passwords enable password cisco Router config e Sets enable password to cisco line con 0 Router config l … password Cisco Router config-line p Continue setting passwords as above … no service password- Router config n Turns off password encryption encryption CAUTION: If you have turned on service password encryption, used it, and then turned it off, any passwords that you have encrypted will stay encrypted.

New passwords will remain unencrypted. With all of the different Cisco devices that are in production networks today, some administrators are becoming confused on the names of their interfaces. The following chart is a sample of some of the different interface names for various routers. This is by no means a complete list.

There must be a clock rate set on every serial link between routers. It does not matter which router has the DCE cable plugged into it, or which interface the cable is plugged into. Serial 0 on one router can be plugged into Serial 1 on another router. Authorized Personnel Only! The delimiting Router config character must surround the banner message and can be any character so long as it is not a character used within the body of the message Setting the Clock Time Zone clock timezone EST —5 Router config c Sets the time zone for display purposes.

The router is set by default to try to resolve any word that is not a command to a DNS server at address If you are not going to set up DNS, turn this feature off to save you time as you type, especially if you are a poor typist. Information items sent to console will not interrupt the command you are typing.

The command will be moved to a new line TIP: Ever try to type in a command and an informational line appears in the middle of what you were typing? Lose your place? The logging synchronous command will tell the router that if any informational items get displayed on the screen, your prompt and command line should be moved to a new line, so as not to confuse you. The informational line does not get inserted into the middle of the command you are trying to type.

If you were to continue typing, the command would execute properly, even though it looks wrong on the screen. Set to 0 0 minutes seconds means console never logs off Router config-line TIP: exec-timeout 0 0 is great for a lab because the console never logs out.

This bad security is very dangerous in the real world. Reload the router to clear the running-config. But plugging the cable back in does not add that static route back into the routing table. The only way to get that route back into the table is to reload the router or use the permanent keyword in your ip route command.

This option is especially useful when the night janitor knocks a cable loose and replaces it, hoping no one will notice Can your network afford to lose a route for a few hours until the next morning when you or your IT staff comes in to work?

However, you must be careful when using this optional keyword. You might want that route to be removed from the routing table. Static Routes and Administrative Distance Optional ip route AD is a number from , where 0 is absolutely trusted, and cannot be trusted at all. There- fore, an AD of 1 is an extremely reliable rating, with only an AD of 0 being better. An AD of 0 is assigned to a directly connected route. The following table lists the administrative distance for each type of route.

By adding an AD number to your ip route statement, however, you can effectively create a backup route to your routing protocol. This is known as a floating static route. Default Routing ip route 0. A static route is described by the letter S. Commands are listed here for reference only. Version 1 is default network w. The autonomous system number AS-number used in the IGRP routing process must match all other routers that are going to share routing updates in order for communication to take place Router config-router network w.

It does not change interface performance. If you are using Cisco IOS A poorly designed network with discontiguous subnets could have problems with connectivity if the summarization feature is left on. You could have two rout- ers advertise the same network— Recommended practice is that you turn off automatic summarization, use the ip summary-address command, and summarize manually what you need to.

The process ID is any value between 1— Uses the wildcard mask to determine which interfaces to advertise. Read this line to say: Any interface with an address of Example 1: An octet of all ones means that the address can be ignored. Example 2: A priority of 0 guarantees that the router never wins a designated router DR election, and guarantees a tie in the election tie broken by highest router ID.

Routing Fundamentals and Subnets Target Audience Anyone desires a practical, technical introduction to the field of networking. High-school, community college, and lifelong-learning students interested in careers as network technicians, network engineers, network administrators, and network help-desk staff.

In addition, instruction and training are provided in the proper care, maintenance, and use of networking software, tools, and equipment and all local, state, and federal safety, building, and environmental codes and regulations. Course Objectives The CCNA certification indicates knowledge of networking for the small-office, home-office SOHO market and the ability to work in small businesses or organizations whose networks have fewer than nodes.

Approximately 35 hours will be designated to lab activities and 35 hours on curriculum content. A case study on structured cabling is required, but format and timing are determined by the Local Academy. What has changed from CCNA versions 2. Course Outline Module 1. Introduction to Networking Overview 1. Networking Fundamentals Overview 2. Networking Media Overview 3.

Cable Testing Overview 4. Author : Glen E. The application layer provides the user interface. The presentation layer determines how data is represented to the user. It is not designed for independent study or professional certification preparation. Publishing in Potomac , MD E - mail : aman