Router RIP Command

To enable a dynamic routing protocol, enter the global configuration mode and use the router command. As shown in the figure, if you type a space followed by a question mark, a list of all the available routing protocols supported by the IOS displays.

To enter the router configuration mode for RIP, enter router rip at the global configuration prompt. Notice that the prompt changes from a global configuration prompt to the following:

R1(config-router)#

This command does not directly start the RIP process. Instead, it provides access to configure routing protocol settings. No routing updates are sent.

If you need to completely remove the RIP routing process from a device, negate the command with no router rip. This command stops the RIP process and erases all existing RIP configurations.

IGP versus EGP

An autonomous system (AS) - otherwise known as a routing domain - is a collection of routers under a common administration. Typical examples are a company's internal network and an Internet service provider's network. Because the Internet is based on the autonomous system concept, two types of routing protocols are required: interior and exterior routing protocols. These protocols are:

• Interior Gateway Protocols (IGP) are used for intra-autonomous system routing - routing inside an autonomous system
• Exterior Gateway Protocols (EGP) are used for inter-autonomous system routing - routing between autonomous systems

The figure is a simplified view of the difference between IGPs and EGPs. The autonomous system concept will be explained in more detail later in the chapter.

Characteristics of IGP and EGP Routing Protocols
IGPs are used for routing within a routing domain, those networks within the control of a single organization. An autonomous system is commonly comprised of many individual networks belonging to companies, schools, and other institutions. An IGP is used to route within the autonomous system, and also used to route within the individual networks themselves. For example, CENIC operates an autonomous system comprised of California schools, colleges and universities. CENIC uses an IGP to route within its autonomous system in order to interconnect all of these institutions. Each of the educational institutions also uses an IGP of their own choosing to route within its own individual network. The IGP used by each entity provides best path determination within its own routing domains, just as the IGP used by CENIC provides best path routes within the autonomous system itself. IGPs for IP include RIP, IGRP, EIGRP, OSPF, and IS-IS.

Routing protocols, and more specifically the algorithm used by that routing protocol, use a metric to determine the best path to a network. The metric used by the routing protocol RIP is hop count, which is the number of routers that a packet must traverse in reaching another network. OSPF uses bandwidth to determine the shortest path.





EGPs on the other hand, are designed for use between different autonomous systems that are under the control of different administrations. BGP is the only currently-viable EGP and is the routing protocol used by the Internet. BGP is a path vector protocol that can use many different attributes to measure routes. At the ISP level, there are often more important issues than just choosing the fastest path. BGP is typically used between ISPs and sometimes between a company and an ISP. BGP is not part of this course or CCNA; it is covered in CCNP.

Classification of Dynamic Routing Protocols

Routing protocols can be classified into different groups according to their characteristics. The most commonly used routing protocols are: RIP, IGRP, OSPF, IS-IS, EIGRP, BGP

• RIP - A distance vector interior routing protocol
• IGRP - The distance vector interior routing developed by Cisco (deprecated from 12.2 IOS and later)
• OSPF - A link-state interior routing protocol
• IS-IS - A link-state interior routing protocol
• EIGRP - The advanced distance vector interior routing protocol developed by Cisco
• BGP - A path vector exterior routing protocol

Physically Connecting a WAN Interface

The WAN Physical layer describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE). Generally, the DCE is the service provider and the DTE is the attached device. In this model, the services offered to the DTE are made available either through a modem or a CSU/DSU.

Typically, the router is the DTE device and is connected to a CSU/DSU, which is the DCE device. The CSU/DSU (DCE device) is used to convert the data from the router (DTE device) into a form acceptable to the WAN service provider. The CSU/DSU (DCE device) is also responsible for converting the data from the WAN service provider into a form acceptable by the router (DTE device). The router is usually connected to the CSU/DSU using a serial DTE cable, as shown.

Serial interfaces require a clock signal to control the timing of the communications. In most environments, the service provider (a DCE device such as a CSU/DSU) will provide the clock. By default, Cisco routers are DTE devices. However, in a lab environment, we are not using any CSU/DSUs and, of course, we do not have a WAN service provider.(more information)

Ethernet Connector

A different connector is used in an Ethernet-based LAN environment. An RJ-45 connector for the unshielded twisted-pair (UTP) cable is the most common connector used to connect LAN interfaces. At each end of an RJ-45 cable, you should be able to see eight colored strips, or pins. An Ethernet cable uses pins 1, 2, 3, and 6 for transmitting and receiving data.

Two types of cables ..

can be used with Ethernet LAN interfaces:

• A straight-through, or patch cable, with the order of the colored pins the same on each end of the cable
• A crossover cable, with pin 1 connected to pin 3, and pin 2 connected to pin 6

Straight-through cables are used for:

• Switch-to-router
• Switch-to-PC
• Hub-to-PC
• Hub-to-server

Crossover cables are used for:

• Switch-to-switch
• PC-to-PC
• Switch-to-hub
• Hub-to-hub
• Router-to-router
• Router-to-server

Connection for WAN

For WAN connections, Cisco routers support the EIA/TIA-232, EIA/TIA-449, V.35, X.21, and EIA/TIA-530 standards for serial connections, as shown. Memorizing these connection types is not important. Just know that a router has a DB-60 port that can support five different cabling standards. Because five different cable types are supported with

this port, the port is sometimes called a five-in-one serial port. The other end of the serial cable is fitted with a connector that is appropriate to one of the five possible standards.(more information)

IBM helps companies in cutting emissions and costs

International Business Machines Corp. (IBM) consulting tool on Thursday that allows both companies to reduce costs and carbon dioxide emissions in the supply chain mereka.hal aim to reduce the bad impact of the environment.

Built with brand-IBM software, Supply Chain Network Optimization Workbench (Snow) to help the client to check the number of distribution centers and they must decide whether to conduct its own production or through third parties.

In tests, the Chinese logistics company and shipper COSCO Ltd system that is used to reduce the number of distribution centers use up to 40 from 100, lowering the cost by 23 percent and cut carbon dioxide emissions by 15 percent, IBM said.

"When you increase the efficiency of the system you can almost automatically reduce costs, waste, and environmental impact," Eric Riddleberger, head of IBM's business strategy consulting practice, said in a statement.

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The Blue Screen of Death and Antivirus 2010

I have to admit that AntiVirus 2010 is one of the better pieces of rogue (fake) anti-spyware out there. If you have fallen into the clutches of this program, I can see how you were easily tricked. These guys worked hard on creating a program that even some of the most experienced computer users might overlook as the real thing. If you think you may have come across AntiVirus 2010, then keep reading. I will tell you some of the tell-tale signs and symptoms and discuss the best removal options..

AntiVirus 2010 is a duplicate copy of AntiVirusXP 2008. It goes by other aliases as well, like Vista Antivirus, Smart Antivirus, and MICRO AV 2009, among several others with similar names. This program uses some of the best scare tactics out there. A moment's hesitation could lead to cleaning out your entire hard drive. It is imperative that you remove it immediately.

You probably want to know how this happened in the first place so it doesn't happen again. The most common way that these spyware programs infect your computer is through a video codec. Have you ever been to a peer to peer (P2P) file sharing community? You may have Windows Security and another antivirus program running that detect nothing on the files that you are about to download.

Rogue anti-spyware programs don't actually hide on the files. They are attached to Trojans that hide in the decoding process of the video codec. Have you been asked to authenticate a certificate when you downloaded something? This is like giving a Trojan permission to infect your computer.

Antivirus 2010 comes on slowly at first. You may notice your computer takes a little longer to start up. Next, come the pop-ups. I could easily see how someone could click on the pop-up under the impression that it is a standard security program that almost all computers have. If you click on the pop-up, the scan starts without your permission. You will be pressured to buy the fake software that will not protect you at all.

If you still haven't bought into it, AntiVirus 2010 has an added feature that I like to call "The Blue Screen of Death." This is that screen that comes up after your computer crashes. The fake blue screen will carry a message about a fake infection called:

d Card Security with Lamination

ID card lamination involves putting a clear layer of PVC over the card surface. Lamination is used..

to protect the card image, particularly for high levels of use where the card is regularly swiped through a magnetic stripe reader or taken out of a wallet every day. Lamination will allow 10,000’s of swipes before any visible wear of the image occurs. ID card lamination is either done at the same time as printing (with an in-line laminator) or separately with a dedicated laminator.

For added security, laminate films containing an optical security logo or hologram are available. These can be both standard or custom.

Many of the security features available in ID cards are also used in banknotes, and some of the manufacturers of laminate films are also banknote producers, so the highest security features are available depending on how much a user wants to pay.

Visual security features that can be incorporated into laminates include :
• Fine-detail printing and complex images (e.g. Guilloche patterns)
• Micro-text
• Nano-text
• Holograms
• Morphing and changing images
• Laser readable images

Standard laminates are those available from a catalogue, with pre-designed features. Custom laminates have features specifically tailored to an end-users needs; e.g. incorporating a government seal.

Visit Ultra Magicard’s website to find out more about ID Card Laminators. Our ID card laminator delivers single-sided and double-sided lamination. Ultra Magicard's Prima 3 printer integrates with the ID card laminator for quick and easy lamination.

Avoid Xpert Antivirus at All Costs!

When you come across Xpert Antivirus, you may be fooled by its charm. You need to be aware of what this program actually is. This program is a rogue anti-spyware program that will pretend to be helpful, but is actually only around to do harm to you and your computer
.

These rogue anti-spyware programs will pretend to be able to scan and remove malicious software (malware) but..

in reality they cannot do either of these functions. Such rogue anti-spyware programs are only able to give you malware that will slow down your computer and possibly rob you of your personal information, including your credit card numbers. With all of this said, when you see Xpert Antivirus, you may not have had any idea that such trouble was brewing.

Xpert Antivirus will appear as a pop-up, and once it does, it will warn you that you are at risk for malware. Please note that computer programs cannot know much of anything about your computer unless they have been downloaded onto your system, so Xpert Antivirus is just trying to get you to believe that it knows something you do not.

Once you are warned about the potential malware problem, Xpert Antivirus will offer you a free scan of your computer to be sure. If you have bought into this, you will always get the free scan. We all love free, especially if it is for the safety of our computer. However, clicking "Ok" on this free scan will allow the program the access it needs to download itself onto your computer without your knowledge.

The results of the scan will typically be a list of your temporary files. Xpert Antivirus will tell you that these files are corrupt and need to be removed—it classifies them as malware. However, these files are not corrupt. If you have just one malware program on your computer it will hard for your operating system to run, so if you had as many corrupt files as Xpert Antivirus claims that you do, then your computer would not be running at all. This scan is a false indicator of any type of malware problem you may be facing.

However, the purpose of this free scan is to gain access to download Xpert Antivirus malware onto your computer, and then to persuade you into purchasing the full version of the program to remove the so-called "malware" that the program has found. Then the real malware will continue to try to record your personal information from your computer and use it to make more of a profit off of you.

To rid yourself of this malware, you need to contact an expert in dealing with these types of programs. Xpert Antivirus is very sneaky and will try to linger as long as it can to make maximum profit off of you. However, if you find a company that offers you a great guarantee on their services, you can rest assured that your malware problem will be taken care of.

Xp Protection Center is Another Rogue Cloning Windows Xp

It’s become one of the oldest tricks in the book. Rogue security programs like XP Protection Center have become rather fond of pretending to be a part of the Windows OS. It’s time to set the record straight.

XP Protection Center, despite its deceptive skin, bears no real resemblance to the actual XP Security Center. Even if it was an actual protection program, XP Protection Center just doesn’t act...

like the real thing.

First of all, the XP Security Center only monitors certain security features on your computer. It lets you know that your Firewall, Automatic Updates and Antivirus Program are running and working correctly. Unlike XP Protection Center, it does not tell you whether or not you’re infected.

Actually, XP Protection Center only tells you that you’re infected once it infects you itself. This whole process goes further, far beyond the scope of the real XP Security Center. The real thing is preinstalled on your computer, and you don’t have to pay for updates or upgrades. You may never see it unless you open it in the Control Panel.

With XP Protection Center, however, it pops up once you’re infected. It does a scan, telling you that your temporary files are infected. In reality, your temporary files are almost never infected. They’re only your Internet browsing history.

Then XP Protection Center tells you that you need to buy the upgrade to kill your infection. You would never see this with the real Security Center. Of course, if you buy it, you open up a whole different can of worms.

If you buy the XP Protection Center “upgrade,” you get a junk program for an insane amount of money. Not only that, but you might have more problems with your credit account. It has been known to happen that whoever is running this program can take every cent out of credit accounts. Unfortunately, they can’t be touched by the United States legal system.

You may also notice that the XP Protection Center web page isn’t on the Windows website. If you weren’t suspicious about it before, this should really clue you in. With Windows products, you will only go to the Windows page.

The biggest difference between the XP Protection Center and the real Security Center is that the first is a bundle of spyware, while the second is a monitoring program that’s part of the Windows OS. The scanning pop up is an old spyware trick, as is the browser redirection. These are all delivered by a Trojan Downloader spyware program called Zlob.

Also, you only get the real XP Security Center as part of your Windows XP Operating System package. You can only get XP Protection Center from infected websites and corrupt downloads. There’s a world of difference in that alone.

Before you even see the fateful pop up screen, you should get a real antispyware program. It should be complete with removal and prevention. Even better, try looking for a 100% removal guarantee, since not all antispyware programs are the same.

Sample Configuration R1 and R3

In this moment, we will be using a simple three router network, as shown in the figure. R1 and R2 share a common 172.16.0.0/16 network with 172.16.0.0/24 subnets. R2 and R3 are connected by the 192.168.1.0/24 network. Notice that R3 also has a 172.16.4.0/24 subnet that is disconnected, or discontiguous, from the 172.16.0.0 network that R1 and R2 share. The effects of this discontiguous subnet will be examined later in this chapter when we look at the route lookup process.

Loopback Interface

Notice that R3 is using loopback interfaces (Lo0, Lo1, and Lo2). A loopback interface is a software-only interface that is used to emulate a physical interface. Like other interfaces, it can be assigned an IP address. Loopback interfaces are also used by other routing protocols, such as OSPF, for different purposes. These uses will be discussed in Chapter 11 OSPF.

In a lab environment, loopback interfaces are useful in creating additional networks without having to add more physical interfaces on the router. A loopback interface can be pinged and the subnet can be advertised in routing updates. Therefore, loopback interfaces are ideal for simulating multiple networks attached to the same router. In our example, R3 does not need four LAN interfaces to demonstrate multiple subnets and VLSM. Instead, we use loopback interfaces.

RFC 1918 Private Addresses

You should already be familiar with RFC 1918 and the reasoning behind private addressing. All the examples in the curriculum use private IP addresses for the inside addressing example.

The RFC 1918-compliant addresses are shown in the table. But when IP traffic is routed across WAN links through an ISP, or when inside users need to access outside sites, a public IP address must be used.

Cisco Example IP Addresses

You may have noticed that the WAN links between R1, R2, and R3 are using public IP addresses. Although these IP addresses are not private addresses according to RFC 1918, Cisco has acquired some public address space to use for example purposes.

The addresses shown in the figure are all valid public IP addresses that are routable on the Internet. Cisco has set these addresses aside for educational purposes. Therefore, this course and future courses will use these addresses when there is a need to use public addresses.

In the figure, R1, R2, and R3 are connected using the 209.165.200.224/27 Cisco public address space. Because WAN links need only two addresses, 209.165.200.224/27 is subnetted with a /30 mask. In the topology, subnet 1 is assigned to the WAN link between R1 and R2. Subnet 2 is assigned to the WAN link between R2 and R3.

What is Variable Length Subnet Masking (VLSM)

Variable Length Subnet Masking (VLSM) allows the use of different masks for each subnet. After a network address is subnetted, those subnets can be further subnetted. As you most likely recall, VLSM is simply subnetting a subnet. VLSM can be thought of as sub-subnetting.

Classfull IP Addressing

When the ARPANET was commissioned in 1969, no one anticipated that the Internet would explode out of the humble beginnings of this research project. By 1989, ARPANET had been transformed into what we now call the Internet. Over the next decade, the number of hosts on the Internet grew exponentially, from 159,000 in October 1989, to over 72 million by the end of the millennium. As of January 2007, there were over 433 million hosts on the Internet.

Without the introduction of VLSM and CIDR notation in 1993 (RFC 1519), Name Address Translation (NAT) in 1994 (RFC 1631), and private addressing in 1996 (RFC 1918), the IPv4 32-bit address space would now be exhausted.

RIP Historical Impact

RIP is the oldest of the distance vector routing protocols. Although RIP lacks the sophistication of more advanced routing protocols, its simplicity and continued widespread use is a testament to its longevity. RIP is not a protocol "on the way out." In fact, an IPv6 form of RIP called RIPng (next generation) is now available.

Click the dates in the figure to compare RIP and network protocol development over time.

RIP evolved from an earlier protocol developed at Xerox, called Gateway Information Protocol (GWINFO). With the development of Xerox Network System (XNS), GWINFO evolved into RIP. It later gained popularity because it was implemented in the Berkeley Software Distribution (BSD) as a daemon named routed (pronounced "route-dee", not "rout-ed"). Various other vendors made their own, slightly different implementations of RIP. Recognizing the need for standardization of the protocol, Charles Hedrick wrote RFC 1058 in 1988, in which he documented the existing protocol and specified some improvements. Since then, RIP has been improved with RIPv2 in 1994 and with RIPng in 1997.

Enchaned Interior Gateway Routing Protocol

Enhanced IGRP (EIGRP) was developed from IGRP, another distance vector protocol. EIGRP is a classless, distance vector routing protocol with features found in link-state routing protocols. However, unlike RIP or OSPF, EIGRP is a proprietary protocol developed by Cisco and only runs on Cisco routers.

EIGRP features include:

• Triggered updates (EIGRP has no periodic updates).
• Use of a topology table to maintain all the routes received from neighbors (not only the best paths).
• Establishment of adjacencies with neighboring routers using the EIGRP hello protocol.
• Support for VLSM and manual route summarization. These allow EIGRP to create hierarchically structured large networks.

Advantages of EIGRP:
Although routes are propagated in a distance vector manner, the metric is based on minimum bandwidth and cumulative delay of the path rather than hop count.
Fast convergence due to Diffusing Update Algorithm (DUAL) route calculation. DUAL allows the insertion of backup routes into the EIGRP topology table, which are used in case the primary route fails. Because it is a local procedure, the switchover to the backup route is immediate and does not involve the action in any other routers.
Bounded updates mean that EIGRP uses less bandwidth, especially in large networks with many routes.
EIGRP supports multiple network layer protocols through Protocol Dependent Modules, which include support for IP, IPX, and AppleTalk.

Routing Information Protokol (RIP)

Over the years, RIP has evolved from a classful routing protocol (RIPv1) to a classless routing protocol (RIPv2). RIPv2 is a standardized routing protocol that works in a mixed vendor router environment. Routers made by different companies can communicate using RIP. It is one of the easiest routing protocols to configure, making it a good choice for small networks. However, RIPv2 still has limitations. Both RIPv1 and RIPv2 have a route metric that is based only on hop count and which is limited to 15 hops.

Features of RIP:
Supports split horizon and split horizon with poison reverse to prevents loops.
Is capable of load balancing up to six equal cost paths . The default is four equal cost paths.

RIPv2 introduced the following improvements to RIPv1:
Includes the subnet mask in the routing updates, making it a classless routing protocol.
Has authentication mechanism to secure routing table updates.
Supports variable length subnet mask (VLSM).
Uses multicast addresses instead of broadcast.
Supports manual route summarization.

What are the Implications of Routing Loops?

A routing loop can have a devastating effect on a network, resulting in degraded network performance or even a network downtime.

A routing loop can create the following conditions:

• Link bandwidth will be used for traffic looping back and forth between the routers in a loop.
• A router's CPU will be strained due to looping packets.
• A router's CPU will be burdened with useless packet forwarding that will negatively impact the convergence of the network.
• Routing updates may get lost or not be processed in a timely manner. These conditions would introduce additional routing loops, making the situation even worse.
• Packets may get lost in "black holes."

What is routing loop

A routing loop is a condition in which a packet is continuously transmitted within a series of routers without ever reaching its intended destination network. A routing loop can occur when two or more routers have routing information that incorrectly indicates that a valid path to an unreachable destination exists.

The loop may be a result of:

• Incorrectly configured static routes
• Incorrectly configured route redistribution (redistribution is a process of handing the routing information from one routing protocol to another routing protocol and is discussed in CCNP-level courses)
• Inconsistent routing tables not being updated due to slow convergence in a changing network
• Incorrectly configured or installed discard routes

Distance vector routing protocols are simple in their operations. Their simplicity results in protocol drawbacks like routing loops. Routing loops are less of a problem with link-state routing protocols but can occur under certain circumstances.

Distance vektor routing protokol

Dynamic routing is the most common choice for large networks like the one shown. Distance vector routing protocols include RIP, IGRP, and EIGRP.

RIP

Routing Information Protocol (RIP) was originally specified in RFC 1058. It has the following key characteristics:
-Hop count is used as the metric for path selection.
-If the hop count for a network is greater than 15, RIP cannot supply a route to that network.
-Routing updates are broadcast or multicast every 30 seconds, by default.

IGRP

Interior Gateway Routing Protocol (IGRP) is a proprietary protocol developed by Cisco. IGRP has the following key design characteristics:
-Bandwidth, delay, load and reliability are used to create a composite metric.
-Routing updates are broadcast every 90 seconds, by default.
-IGRP is the predecessor of EIGRP and is now obsolete.

EIGRP

Enhanced IGRP (EIGRP) is a Cisco proprietary distance vector routing protocol. EIGRP has these key characteristics:
-It can perform unequal cost load balancing.
-It uses Diffusing Update Algorithm (DUAL) to calculate the shortest path.
-here are no periodic updates as with RIP and IGRP. Routing updates are sent only when there is a change in the topology.

Purpose of Administrative Distance

Administrative distance (AD) defines the preference of a routing source. Each routing source - including specific routing protocols, static routes, and even directly connected networks - is prioritized in order of most- to least-preferable using an administrative distance value. Cisco routers use the AD feature to select the best path when it learns about the same destination network from two or more different routing sources.

Administrative distance is an integer value from 0 to 255. The lower the value the more preferred the route source. An administrative distance of 0 is the most preferred. Only a directly connected network has an administrative distance of 0, which cannot be changed.

It is possible to modify the administrative distance for static routes and dynamic routing protocols. This is discussed in CCNP.

An administrative distance of 255 means the router will not believe the source of that route and it will not be installed in the routing table.

Purpose of metric

To select the best path, the routing protocol must be able to evaluate and differentiate between the available paths. For this purpose a metric is used. A metric is a value used by routing protocols to assign costs to reach remote networks. The metric is used to determine which path is most preferable when there are multiple paths to the same remote network.
For example, RIP uses hop count, EIGRP uses a combination of bandwidth and delay, and Cisco's implementation of OSPF uses bandwidth. Hop count is the easiest metric to envision. The hop count refers to the number of routers a packet must cross to reach the destination network. For R3 in the figure, network 172.16.3.0 is two hops, or two routers away.

The Evolution of Dynamic Routing Protocols

Dynamic routing protocols have been used in networks since the early 1980s. The first version of RIP was released in 1982, but some of the basic algorithms within the protocol were used on the ARPANET as early as 1969.

One of the earliest routing protocols was Routing Information Protocol (RIP). RIP has evolved into a newer version RIPv2. However, the newer version of RIP still does not scale to larger network implementations. To address the needs of larger networks, two advanced routing protocols were developed: Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS). Cisco developed Interior Gateway Routing Protocol (IGRP) and Enhanced IGRP (EIGRP), which also scales well in larger network implementations.

Introducing the routing table

The primary function of a router is to forward a packet toward its destination network, which is the destination IP address of the packet. To do this, a router needs to search the routing information stored in its routing table.

A routing table is a data file in RAM that is used to store route information about directly connected and remote networks. The routing table contains network/next hop associations. These associations tell a router that a particular destination can be optimally reached by sending the packet to a specific router that represents the "next hop" on the way to the final destination. The next hop association can also be the outgoing or exit interface to the final destination.

The network/exit-interface association can also represent the destination network address of the IP packet. This association occurs on the router's directly connected networks.

A directly connected network is a network that is directly attached to one of the router interfaces. When a router interface is configured with an IP address and subnet mask, the interface becomes a host on that attached network. The network address and subnet mask of the interface, along with the interface type and number, are entered into the routing table as a directly connected network. When a router forwards a packet to a host, such as a web server, that host is on the same network as a router's directly connected network.

A remote network is a network that is not directly connected to the router. In other words, a remote network is a network that can only be reached by sending the packet to another router. Remote networks are added to the routing table using either a dynamic routing protocol or by configuring static routes. Dynamic routes are routes to remote networks that were learned automatically by the router, using a dynamic routing protocol. Static routes are routes to networks that a network administrator manually configured.

Note: The routing table-with its directly-connected networks, static routes, and dynamic routes-will be introduced in the following sections and discussed in even greater detail throughout this course.

The following analogies may help clarify the concept of connected, static, and dynamic routes:
Directly Connected Routes - To visit a neighbor, you only have to go down the street on which you already live. This path is similar to a directly-connected route because the "destination" is available directly through your "connected interface," the street.
Static Routes - A train uses the same railroad tracks every time for a specified route. This path is similar to a static route because the path to the destination is always the same.
Dynamic Routes - When driving a car, you can "dynamically" choose a different path based on traffic, weather, or other conditions. This path is similar to a dynamic route because you can choose a new path at many different points on your way to the destination.

The show ip route command

As shown in the figure the routing table is displayed with the show ip route command. At this point, there have not been any static routes configured nor any dynamic routing protocol enabled. Therefore, the routing table for R1 only shows the router's directly connected networks. For each network listed in the routing table, the following information is included:
C - The information in this column denotes the source of the route information, directly connected network, static route or a dynamic routing protocol. The C represents a directly connected route.
192.168.1.0/24 - This is the network address and subnet mask of the directly connected or remote network. In this example, both entries in the routing table, 192.168.1./24 and 192.168.2.0/24, are directly connected networks.
FastEthernet 0/0 - The information at the end of the route entry represents the exit interface and/or the IP address of the next-hop router. In this example, both FastEthernet 0/0 and Serial0/0/0 are the exit interfaces used to reach these networks.

When the routing table includes a route entry for a remote network, additional information is included, such as the routing metric and the administrative distance. Routing metrics, administrative distance, and the show ip route command are explained in more detail in later chapters.

PCs also have a routing table. In the figure, you can see the route print command output. The command reveals the configured or acquired default gateway, connected, loopback, multicast, and broadcast networks. The output from route print command will not be analyzed during this course. It is shown here to emphasize the point that all IP configured devices should have a routing table.

router are computers

A router is a computer, just like any other computer including a PC. The very first router, used for the Advanced Research Projects Agency Network (ARPANET), was the Interface Message Processor (IMP). The IMP was a Honeywell 316 minicomputer; this computer brought the ARPANET to life on August 30, 1969.

Note: The ARPANET was developed by Advanced Research Projects Agency (ARPA) of the United States Department of Defense. The ARPANET was the world's first operational packet switching network and the predecessor of today's Internet.

Routers have many of the same hardware and software components that are found in other computers including:
CPU
RAM
ROM
Operating System