|
|
 SIGN
UP FOR FREE |
|
|
|
Sign Up for a free account or
learn more. |
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
Most Recent Articles
|
- Ccnp Certification Bcmsn Exam Tutorial: Mac Address Flooding
Network attacks take many forms, and it's important to know how the potential security issues with ARP, DHCP, and MAC addresses. They're innocent looking enough, but each of these common network protocols and addresses can be turned against us. Today, we'll talk about what MAC Address Flooding is, how it can be used against our network, and the best defense against this attack.
A MAC Address Flooding attack is an attempt by a network intruder to overwhelm the switch memory reserved for maintenance of the MAC address table. The intruder generates a large number of frames with different source MAC addresses - all of them invalid. As the switch's MAC address table capabilities are exhausted, valid entries cannot be made - and this results in those valid frames being broadcast instead of unicast. - Cisco Ccnp Bcmsn 642-812 Certification Exam Tutorial: Dhcp Snooping
An important part of passing the Cisco CCNP BCMSN exam and protecting your network from intruders is to recognize that even everyday protocols and services can work against us once that intruder is in our network.
It may be hard to believe, but something as innocent as DHCP can actually lead to trouble for your network. When a host sends out a DHCPDiscovery packet, it listens for DHCPOffer packets - and accepts the first Offer it gets! - Cisco Ccnp Bsci 642-901 Exam: Ospf And Passive Interfaces
Your BSCI exam may well be the most challenging of the four exams you must pass to become a CCNP, so you have to have the details of every protocol on the exam mastered! Today, we'll look at the passive-interface command as it relates to OSPF.
Passive interfaces accept routing updates, but do not send them. Regarding OSPF, even though OSPF does not sent "routing updates" in the form that RIP, IGRP, and EIGRP do, you can still configure an OSPF-enabled interface as passive in order to prevent OSPF traffic from exiting that interface. No OSPF adjacency can be formed if one of the interfaces involved is a passive interface, and if you configure an OSPF-enabled interface as passive where an adjacency already exists, the adjacency will drop almost immediately. - Microsoft Vista Certification Tutorial: An Introduction To Windows Defender
You don't have to be working on a Microsoft Windows Vista certification to know about the security problems that past versions of Windows have encountered. As a result, Microsoft is paying special attention to security with Vista, and one of the new features Vista features is Windows Defender.
What exactly are we defending against with Defender? Spyware. Spyware programs range from annoying (one pop-up banner after another) to downright destructive (capturing your computer's keystrokes). Windows Defender is designed to operate much like an antivirus program in that Defender will detect the offending spyware and then quarantine or delete the spyware. - Cisco Ccna / Ccnp Certification Exam Tutorial: Eigrp And Split Horizon
EIGRP is a major topic for your CCNA and CCNP studies, and one basic skill you’ll need to pass your Cisco certification exams is to identify situations where you need to enable or disable split horizon. EIGRP commands tend to be a little different than those used with other protocols, so let’s take a look at how EIGRP and split horizon interoperate.
R1 is our hub router, with R2 and R3 as the spokes. There are no subinterfaces, and each router is advertising a single loopback network using its router number for each octet. R1 will see both R2 and R3’s loopback network, but the spokes will not have a route to the other spoke’s loopback. “show ip route eigrp” verifies this. - Cisco Ccnp Bsci 642-901 Tutorial: Clear Text Ospf Neighbor Authentication
An OSPF adjacency can be authenticated with MD5 (Message Digest 5) or with a clear-text password. I’m not much on clear-text passwords, and hopefully you aren’t either! Whether you’re working in the real world or the certification exam room, though, it’s always a good idea to know more than one way to do things. Let’s take a look at how to configure clear-text authentication of an OSPF neighbor relationship.
The commands we’ll use are “ip ospf authentication-key” and “ip ospf authentication”. In this example, we have preexisting adjacencies between three routers in an OSPF NBMA network. The hub router (R1) has an adjacency with two spoke routers, R2 and R3. - Cisco Ccnp 642-901 Bsci Exam Tutorial: Eigrp Adjacencies And Secondary Addresses
I've read some non-Cisco documentation that EIGRP will not allow adjacencies to form when secondary addresses are used. This is incorrect, but there is one common error that can result if both addresses are not secondary. To fully prepare for the 642-901 BSCI exam, you should know about this error. Let's take a look at R2 and R3, which will be using secondary addresses to form an EIGRP adjacency across an ethernet segment.
R2(config)#interface ethernet0 - Cisco Ccnp Certification Bsci 642-901 Exam Training: The Eigrp Adjacency
EIGRP is an important part of real-world networking as well as being a major topic on the 642-901 CCNP BSCI exam. As with any networking topic, before you try to master intermediate and advanced skills, you must master the fundamentals. It doesn’t get any more fundamental than the EIGRP adjacency process – and it doesn’t get any more important, because without that adjacency, we don’t have an EIGRP deployment!
In today’s CCNP tutorial, we’ll work with R1 and R2, two Cisco routers communicating over a serial interface. EIGRP is already running on R2’s serial interface, but was just enabled on R1’s serial interface. The EIGRP adjacency process begins with R1 sending an EIGRP Hello packet to the multicast address 224.0.0.10 in an attempt to find potential neighbors. - Cisco Tac : An Introduction To The Cisco Technical Assistance Center
The Cisco Technical Assistance Center (TAC) is Cisco's tech support center, and they've got some very talented people working there. Before you pick up the phone to call the TAC, though, you should do your best to resolve the problem and document each step along the way. One of the first things the TAC will do is ask what you've done so far to resolve the issue, and giving them an accurate answer is a huge step toward getting the problem resolved.
If you're used to "tech support" where calls are prioritized by the order in which they come in, the TAC will open your eyes! Cisco's TAC uses four priority levels to determine which cases should be handled first: - Cisco Ccnp Cit Exam Training: Creating A Network Baseline
The first thing we've got to do in order to document our network is to create a network baseline. After all, if we don't know our goals, we can't accomplish them. A baseline is really a "network snapshot", a picture of our network devices and their performance - which also helps us spot issues before they happen.
Every network has its "breaking point", the point at which it can no longer transfer data effectively. By creating a baseline, you can see what the current network load is now - and by maintaining that baseline, you can spot network issues well before they become critical. For example, say you baseline all your network routers, and part of that is noting the CPU capability and usage. By maintaining the network baseline, you can note smaller, gradual increases in CPU usage and do something about it before the situation becomes critical. - Cisco Ccna And Ccnp Bcran Exam Training: Frame Relay Pvc, Svc, Dlci, And Map Statements
In today's CCNP certification tutorial, we'll concentrate on the BCRAN exam and Frame Relay PVCs, SVC, and DLCIs in particular.
There are actually two kinds of virtual circuits - Permanent Virtual Circuits (PVCs) and Switched Virtual Circuits (SVCs). An SVC doesn't have anything to do with an L2 switch - it's a VC that is built only under predefined circumstances, similar to an ISDN connection that is only built when interesting traffic hits the line. SVCs go through a basic four-step process, and it's a lot like ISDN: - Ccna Certification Exam Training: Do Your Best And Get Some Sleep!
CCNA certification is tough enough without you making it tough on yourself. There are a few simple things you can do that will increase your exam day performance greatly. Let's take a look at these simple yet powerful techniques.
First, get plenty of sleep the night before. I've taken certification exams from the CCNA to the CCIE, and I'm always amazed at the number of bleary-eyed test takers that show up at the testing center looking like they're about to fall asleep. Don't cram the night before - if you don't know it by 10 PM the night before the exam, you just don't know it. In the words of Dave Attell, "Get some sleep!" - Microsoft Vista Certification Exams Announced
Microsoft Vista certification is on the way, and Microsoft recently announced the first Vista exams. In keeping with trends in certification, these particular exams are designed for different job roles. These exams are scheduled to be released in "early 2007", according to Microsoft's website:
MCITP - Microsoft Certified IT Professional - "Consumer Support Technician" and "Enterprise Support Technician" certifications - Cisco Ccna Certification: The Proper Use Of Default Static Routes
Earning your Cisco CCNA certification means knowing the details of Cisco routing, and that includes knowing when Cisco routing terms don't quite mean what they sound like they mean. For example, the general meaning of "default" is a setting that is used unless you or I change it. On the other hand, a default route is a route taken by packets that have no other route they can take. Let's take a look at how a default static route is configured and used on a Cisco router.
Here's our current routing table: - Ccna Certification: Three Occasions To Reload Or Reopen A Cisco Router Interface
Passing the CCNA certification exam means that you know how to configure and troubleshoot a Cisco router instead of using what I call the "hope method" - you know, "Let's reload the router and hope that takes care of it." The majority of Cisco router configurations take effect without the need for a reload, but every once in a while you just have to reload a router or shut and reopen an interface. Let's take a look at three such scenarios.
The first is when you change an OSPF Router ID from its default. For the new RID to take effect, you must either reload the router or clear the OSPF process, which means that all existing adjacencies will come down. Cisco routers are kind enough to tell you this with the following message after you configure a new RID: "Reload or use "clear ip ospf process" command, for this to take effect". - Ccna Certification Training: Configuring Static Routes On A Cisco Router
The great thing about CCNA certification training is that the skills you learn will truly come in handy when working with Cisco routers and switches in production networks. That's particularly true of static route configuration. While most networks use dynamic routing protocols such as RIP, EIGRP, and OSPF to build routing tables, static routes still come in handy sometimes - especially if a routing protocol configuration goes awry.
Let's say that you just added a new segment to your network and you've successfully added it to your network's routing tables. Suddenly, on Monday morning, users on that segment can't get to a network resource such as an email server, or they can't get out to the Internet. We all know what it's like to try to fix something while the phone's ringing like crazy. That's when we have to do two things. - Cisco Ccna Certification Training: Etherchannels And Spanning Tree Protocol (stp)
Cisco CCNA certification looks great on your resume, and it also teaches you vital real-world networking skills. One exam topic that you'll definitely see in today's networks is the configuration of an Etherchannel on a Cisco router. You need to know how to build and verify one - so let's build one right now!
In this Cisco training tutorial, we'll use two switches that are connected at ports 0/11 and 0/12 via crossover cables. SW1 is the root bridge, SW2 is the non-root bridge. Even though there are two separate physical connections, spanning tree protocol (STP) will only allow the use of one, as verified by the partial output of "show spanning vlan 1" on SW2. - Cisco Ccnp Certification Training Tutorial: The New Ont 642-845 Exam
The Cisco CCNP certification is changing at the end of 2006, with the BSCI and BCMSN exams being updated and the BCRAN and CIT exams being dropped. One of the two new exams is the 642-845 Optimizing Converged Cisco Networks (ONT) test, and the name of the exam doesn't give many hints as to the material covered!
According to Cisco's exam blueprint, the major topics on this new exam will be Voice over IP (VoIP) and Quality of Service (QoS). This exam change is an excellent move on Cisco's part, since VoIP is one of the fastest-growing network technologies today, and implementing VoIP demands the ability to implement QoS! - Cisco Ccna Certification Training Tutorial: Ppp Multilink And Isdn Bri
Earning your CCNA certification means you have to notice details about Cisco routers that others might miss, and that's true in the exam room and on the job. In today's tutorial, we'll take a look at multilink PPP - a topic that seems simple enough, but has details that trip up some CCNA certification candidates.
ISDN BRI (Basic Rate Interface) has two B-channels that both carry data, and they each have a capacity of 64 KBPS. Interestingly enough, they don't share the load by default - the first channel has to be at capacity before the second channel starts taking some of the load. It's more efficient to have the channels share the load before then, and we can do just that by configuring PPP multilink. (Note that it's called PPP multilink for a reason. We can't configure it if the BRI interface is running at the default of HDLC.) - Cisco Ccnp Certification Training Tutorial: The New 642-825 Iscw Ccnp Exam
Cisco CCNP certification is getting a brand-new look, and that new look includes two new exams! The BCRAN and CIT exams are retiring at the end of 2006, and the exam replacing the BCRAN is the 642-825 Implementing Secure Converged Wide Area Networks exam, which is thankfully known as ISCW.
The key word in this Cisco exam is "secure". Very few of the BCRAN topics are moving to the ISCW exam, and an emphasis is being placed on VPNs and network security configurations and methods. According to Cisco's exam blueprint, the only BCRAN topics you can expect to possibly see on the ISCW exam are PPPoE and PPPoA. The importance of network security has never been higher, and it's to Cisco's credit that their new CCNP exams are emphasizing security. - Ccna Cisco Certification Training Case Study: How Multiple Passwords Affect Router Access
Your CCNA certification exam efforts must include practicing with different password types and knowing how to configure them on a Cisco router - but for CCNA exam success and to thrive in real-world networks, you also have to know how to examine a Cisco router configuration and determine the level of network security that is already present. After all, most routers you work with already have passwords set, and it's up to you to determine if those passwords are getting the job done.
Let's start with a telnet password. Telnet passwords are configured on the VTY lines, and no telnet access is enabled on a Cisco router by default. If you saw the following configuration, what would it mean? - Yahoo And The Peanut Butter Manifesto
One of the great internal battles at any successful company is the desire to expand versus the desire to branch out into other areas. After all, if an organization is wildly successful at one thing, they usually feel that they can be successful at anything.
That line of thinking is particularly true at Yahoo, Google, and MSN, today's three largest search engines. All three companies are continually expanding, and a senior executive at Yahoo recently sent an internal memo that basically said Yahoo is spreading itself too thin. Nothing unusual there, since it's common for executives at rapidly-expanding companies to guard against such things - but the comparison the exec used to draw this conclusion was rather unusual. - Cisco Ccna Certification Exam Training: Telnet, Passwords, And Privilege Levels
Your CCNA certification exam is likely going to contain questions about Telnet, an application-level protocol that allows remote communication between two networking devices. With Telnet use being as common as it is, you had better know the details of how to configure it in order to pass your CCNA exam and to work in real-world networks.
The basic concept is pretty simple - we want to configure R1, but we're at R2. If we telnet successfully to R1, we will be able to configure R1 if we've been given the proper permission levels. In this CCNA case study, R2 has an IP address of 172.12.123.2 and R1 an address of 172.12.123.1. Let's try to telnet from R2 to R1. - Cisco Ccnp Certification Training : The New Ccnp Bcmsn 642-812 Exam
Cisco CCNP certification is about to become more valuable and more difficult! Cisco is making major changes to the CCNP certification program, retiring two exams (BCRAN and CIT) while updating two old friends, the BSCI and BCMSN exam. Today, we'll take a look at the changes in the Building Converged Cisco Multilayer Switched Networks (BCMSN) exam.
According to Cisco's exam blueprint, there are some major additions with the introduction of the 642-812 exam. Wireless access, security, and voice are all rapidly growing features and concerns in today's real-world networks, and Cisco is responding to that by adding all three of these topics to the CCNP BCMSN exam. Cisco CCNP candidates should expect to be questioned on WLANs as well as wireless clients. - Ccna Certification Exam Training: Passwords, Cisco Routers, And Network Security
CCNA certification is important, and so is securing our network's Cisco routers! To reflect the importance of network security, your CCNA certification exam is likely going to contain a few questions about the various passwords you can set on a Cisco router. Let's take a look at some of those passwords and when to apply them.
If the previous user has logged out of the router properly, you will see a prompt like this when you sit down at the router console: - Cisco Ccnp Certification Training: What's New On The Bsci 642-901 Exam?
CCNP certification is getting a new look at the end of 2006. The BSCI and BCMSN exams are being updated, and the CIT and BCMSN exams are being retired. Let's take a look at what to expect from the new BSCI exam.
According to Cisco's exam blueprint - admittedly a very broad blueprint at this time - the major new topics are IP version 6 (IPv6) and multicasting. The addition of these two topics will make an already demanding Cisco certification exam that much tougher, but this is a great change for the exam and for the candidate. IPv6 is just going to become more and more prevalent in today's networks, and multicasting is as well. - Ccna Certification Exam Training: Circuit Switching Vs. Packet Switching
CCNA certification exam training is all about learning the details, and an important part of your CCNA test prep is knowing the differences between Cisco router and switch technologies that are somewhat similar. Packet switching and circuit switching are both methods of getting packets from "point A" to "point B", but the methods used are very different - and you must know these differences to earn your Cisco CCNA certification.
In my last CCNA training tutorial, I discussed packet switching. In case you missed that article, packet switching is a method of transporting packets from source to destination via different paths; that is, the packets will not necessarily share the same physical path. The packets are put into their proper order at the destination. Packet switching is highly effective, but should not be used for delay-sensitive traffic such as voice or video packets. Not only is Frame Relay a big topic for your CCNA certification exam, it's also an excellent example of a packet-switching technology. - Cisco Ccna Certification Exam Case Study: Frame Relay, Pings, And Routing Protocols
Cisco CCNA certification training includes troubleshooting your own work and that of others. The best CCNA training you can do is indeed troubleshooting your own Cisco router and switch configurations - as I'm always telling my students, "I can guarantee that any error you make has been made before, and you'll probably see it again one day." One such common error involves two very important Cisco CCNA certification topics - Frame Relay and routing protocols.
A student was working on her Cisco CCNA exam home lab and came up with an interesting problem. He set Frame Relay up in a hub-and-spoke configuration with R1 as the hub and R2 and R3 as the spokes. He wrote the following frame map statements: - Cisco Ccna Certification Exam Training: What Is Packet Switching?
Cisco CCNA certification exam training means you've got to learn a lot of new terms, and some of them can be a little confusing at first. To pass this tough certification exam, one term you definitely need to understand is packet switching. The first question, of course, is "What is packet switching in the first place?" Let's define this term in today's Cisco CCNA exam prep tutorial.
Packets transmitted from "point A" to "point B" all have to arrive at the same destination, but with packet switching, they do not all have to take the same path to get there. If you and I are standing 10 feet apart and I want to throw a basketball to you, I've got a couple of options. I could bounce the ball off the floor to you, I could throw it straight at you, or I could throw it high into the air to you. Packet switching is really the same thing - packets will take different paths to get from source to destination, but the end result is that all the packets arrive at the destination. The packets are then reassembled to take the form of the original message. - Cisco Ccna Certification Exam Tutorial: The Config Register And Password Recovery
Whether you're preparing for the CCNA certification exam or not, you must be prepared for the following question:
"Hey, I reloaded this router and it wants an enable password. Do you know it?" - Comptia Network+ Certification Exam Tutorial: Antivirus Programs
In the first part of this CompTIA Network+ certification exam tutorial, we looked at the different types of viruses and other invaders trying to get into our network, and how antivirus programs help to stop them. Today, we’ll discuss some tips on how to get the maximum protection from your antivirus program.
I strongly recommend you choose an antivirus program that offers automatic updates. If you rely on manual updates - that is, relying on remembering to go out and check for updates yourself instead of having them automatically downloaded when new updates are available - I can practically guarantee you're going to forget to do so, and this can be a fatal mistake for both your network and your career. - Comptia Network+ Certification Exam Tutorial: Virus Attacks And Antivirus Programs
Whether you’re preparing to pass the Network+ or Cisco CCNA certification exam or not, you must not underestimate the importance of antivirus programs and virus definition updates. With all the attention we pay to viruses and their prevention, I feel a little silly even saying that. But….
If there's one thing you must have working at full capacity in your network, it's the antivirus programs. - Network+ / Ccna Certification Exam Tutorial: Port Numbers And Troubleshooting
Passing the Network+ and CCNA exams demands that you know quite a few port numbers, but they're important to know when working with real-world networks as well. Before we discuss why, here's a partial list of important port numbers to know for these certification exams:
Ports 20 and 21 are used by File Transfer Protocol (FTP). - Comptia Network+ Certification Exam Tutorial: The Five Ip Address Classes
Passing the CompTIA Network+ certification exam and going on to become a subnetting expert is mastering the basics of IP addressing, and that means knowing the different classes, their default masks, and what these masks mean. Let’s get started!
Part of every IP address indicates the network the host is part of, and the other part identifies that particular host. You need to be able to look at an IP address and determine the network and host portions, and you do that by determining the class of the address. - Comptia Network+ Certification Exam Tutorial: Hubs, Repeaters, Bridges, And Switches
To pass your Network+ certification exam, you must know the differences between hubs, repeaters, bridges, and switches. The differences are straightforward for the most part, so let's examine the basic purpose of these devices.
Hubs and repeaters both work at the Physical layer of the OSI model. They do not help to direct traffic toward the proper destination, as routers and switches do. Their purpose in the network is simply to make the signal strong enough to reach its destination, by regenerating the signal. Hubs and repeaters both take an incoming data signal and make a clean, strong copy of the signal. Otherwise, the signal would suffer from attenuation, the gradual weakening of a signal as it gets farther and farther away from the source. - Comptia Network+ Certification Exam Tutorial: Dhcp And Dhcp Relay Agents
As a CompTIA Network+ exam candidate, you’re probably familiar with DHCP – but just in case, we’re going to review DHCP basics here and then go into a discussion of DHCP Relay Agents.
When it comes to assigning an IP address to all the PCs on our network, along with their network mask, DNS server location, and more, we've got two choices on how to do it: - Comptia Network+ Certification Exam Tutorial: Hot Sites, Warm Sites, And Disaster Recovery
Part of passing the Network+ exam and being an outstanding network administrator is being prepared for disaster. Sometimes that's a disaster on a relatively small scale, such as a drive failure. If you're running data backups on a regular basis (and you are, aren't you?), you're prepared for that issue.
What is your network's disaster recovery plan from a true disaster, either natural or man-made? What if the entire building your servers are in disappeared tonight? What is your plan if that happens? In today's world, that's not a rhetorical question. Disaster recovery is taken to the next level by preparing a cold site, warm site, or hot site at another physical location. - Network+ Exam Tutorial: Becoming A Master Troubleshooter
Passing your Network+ exam is the first step on the way to becoming a master network troubleshooter, and that's where you need to be. The average network admin spends 90% of their time troubleshooting and 10% installing hardware and software, so you better be good at troubleshooting!
In my experience, there are two kinds of network troubleshooters in the world: - Network+ Exam Tutorial: Network Interface Cards (nics)
Part of the challenge of passing the Network+ exam is learning about all the different types of hardware a network requires. Today we’ll take a look at a vital part of network connectivity, the Network Interface Card (NIC, pronounced “nick”).
The NIC is the device, or card, that gives the host a physical connection to the network. The NIC is generally an internal device, but one that can be removed and replaced with a different NIC. NICs are considered Physical layer devices and work at Layer 1 of the OSI model. - Ccna Exam Tutorial: Mac Addressing Formats And Broadcasts
Your CCNA exam success depends on your mastery of networking, routing, and switching fundamentals. Those fundamentals have to include knowledge of MAC addresses, so let’s take a close look at Media Access Control addressing.
A typical MAC address looks something like this: - Network+ Certification Exam Tutorial: How And When To Use Virtual Lans (vlans)
From your Network+ exam studies, you know that switches forward broadcasts, and that sounds great, but that's not always a good thing. A switch can have anywhere from 12 ports to 80 or more, and by default all hosts connected to that switch are going to be in the same broadcast domain. Let's say we have an 80-port switch. If one host connected to that switch sends a broadcast, by default, all of the other 79 hosts are going to receive the broadcast. That will unnecessarily take up our network's available bandwidth.
It gets worse. For some network services and protocols, a broadcast received by a host results in that receiving host transmitting a broadcast of its own. Then when all the hosts receive that broadcast, they all end up transmitting even more broadcasts. Pretty soon, all these broadcasts have snowballed into a broadcast storm, which can take up most of a network's bandwidth and make normal network operations almost impossible. - Network+ Exam Tutorial: Ports, Port Numbers, And Sockets
If there's one thing that can be a bit confusing to many Network+ certification exam candidates, it's the concept of ports and sockets. Well, it was confusing to me when I got started with computer certifications! Let's take a look at ports and sockets, and why we need them in the first place.
Past Network+ exam tutorials have focused on how two PCs start communicating, but what we've got to keep in mind is that host PCs may and probably will have several different kinds of communications going on at the same time. A single PC may be sending email, receiving a Telnet request, and accessing the Internet at the same time. These conversations have to kept separate.. but how? - Network+ Exam Certification Tutorial: The Bus Topology
The Physical layer of the OSI model isn't the most exciting or interesting to work with, but it's the foundation for everything we do in networking. The same goes for the physical side of networking - whether it's cable types, network topologies, or network cards, it's not necessarily the most exciting study you'll ever do, but it is the most important. After all, if a network has physical issues such as a bad Network Interface Card or mismatched cables, there's no way the network can work properly!
My next few Network+ exam tutorials will discuss the different network topology types, and we’ll start with a look at the dreaded bus topology. After we define it, I'll tell you why I call it "dreaded". - Network+ Certification Exam Tutorial: Dhcp And Rarp
Part of passing the Network+ exam is mastering the many different protocols and services you're introduced to in your studies, and that's especially hard when two protocols do much the same thing! That's the case with RARP and DHCP, so let's take a close look at these two protocols and why we use them in the first place.
Whether you've been around networks for a while or are just getting started with your IT career, you'll quickly notice that many basic tasks in networking can be handled either statically or dynamically. By "statically", I mean configuring each device in question manually; by "dynamically", I mean having it done (almost) automatically. Generally, you're going to choose the dynamic method, and not because it's easier or quicker - it's because dynamic methods are much more adaptable to change, and today's networks are always changing. - Network+ Certification Exam Tutorial: Arp And Proxy Arp Explained
In yesterday's Network+ tutorial, we talked about the importance of Address Resolution Protocol (ARP) in today's networks. A host PC must have the MAC and IP addresses of a remote host in order to send data to that remote host, and it's ARP that allows the local host to request the remost host to send the local host its MAC address through an ARP Request.
The ARP Request is a layer two broadcast, and like all L2 broadcasts it has a destination MAC address of ff-ff-ff-ff-ff-ff. Switches forward broadcasts, but routers do not, which brings up a basic problem. If there's a router between two hosts, how can one possibly send an ARP Request to the remote host, since routers do not forward broadcasts? - Cisco Ccnp Certification Exam Tutorial: Making The Most Of Cisco's Ccnp Program Changes
As you probably know by now, Cisco's making some sweeping changes in their Cisco Certified Network Professional (CCNP) program. Two longtime exams are being retired at the end of the year, two are being revised, and two new exams will be making their debut in late 2006.
If you're currently working on the CCNP or even thinking about it, the one thing you must NOT do is postpone your studies. On occasion, some certification exam candidates postpone their studies when they hear of an exam change. Cisco has announced these CCNP changes well ahead of time, and you've got plenty of time to pass some CCNP exams by the end of the year - and they still count toward the CCNP! - Network+ Certification Exam Tutorial: Address Resolution Protocol (arp)
When you're studying for the Network+ exam, you've got to master the fundamentals of networking, because the Network+ is a hard exam to pass due to the range of information covered. One such fundamental is the Address Resolution Protocol, commonly referred to as ARP.
ARP operates at the Data Link layer of the OSI model, and its purpose is often overlooked. When Host A wants to send data to Host B, we know Host A must have a destination IP address for Host B (the Network layer address). What we tend to overlook is that Host A must also have a Layer 2 destination address for Host B -- in other words, it's got to have a destination MAC address for Host B. That's where ARP comes in. - Ccna / Network+ Certification Exam Tutorial: Collision Domains And Switches
In the previous Network+ exam tutorial, we talked about how collisions occur when data sent by two hosts on a shared Ethernet segment transmit data at the exact same time. Collisions result in the colliding data being unusable, which means the hosts must retransmit the data - and all this extra activity slows the network down!
Carrier Sense Multiple Access with Collision Detection helps limit the number of collisions, but by dividing one large collision domain into smaller collision domains, we can further reduce or actually eliminate the number of collisions. That's where switches come in! - Network+ Certification Exam Tutorial: Ethernet Csma/cd Explained
When you're studying for the Network+ exam, you've got a lot of new acronyms to learn! One of the basics is CSMA/CD, which stands for Carrier Sense Multiple Access with Collision Detection. That's quite a mouthful, but it's an important term to know for both your exam and real-world success.
On an Ethernet segment, hosts can send data at any time. As you might guess, that's a bit of a problem in itself, because if multiple hosts send data at the same time, a collision will occur and the data will become unusable. That's why CSMA/CD requires a host that wants to send data to listen first. Listen for what? Data being sent by another host. If the host hears data being transmitted, that host will not begin sending data itself. That's the "carrier sense" part of CSMA/CD. If that host hears nothing, the host will begin to transmit. - Cisco Ccna / Ccnp Home Lab Tutorial: The 2520 Router
I hear from CCNA and CCNP candidates every day, and the most common question is "What routers and switches should I buy for my home lab?" There is no one right answer to this question, since every test candidate has a different budget. There are also CCNA candidates who want to go on to the CCNP and want to know what routers and switches are best for future study. Again, there's no one right answer, but there are routers that fit every budget and every study plan - and the Cisco 2520 router is the king of home study labs.
The 2520 has four serial ports, one ethernet port, and a BRI port. You can use a 2520 as a frame relay switch, and still have ports to spare to practice routing protocols and directly connected serial interfaces. I know ISDN home simulators are still expensive if bought new, but you can get a used one on eBay and go from there. Even if you choose not to buy an ISDN simulator now, the 2520 gives you that opportunity for future home lab growth - and "planning for future growth" is important when it comes to your home lab as well as production networks! - Cisco Ccna / Ccnp Certification Exam Tutorial: Troubleshooting Eigrp
Part of earning your CCNA and CCNP - especially passing the difficult CIT exam - is becoming a master network troubleshooter. Today, we'll take a look at troubleshooting EIGRP and spotting common errors.
Most adjacency issues are easily resolved - mistyped IP address, bad wildcard mask in the neighbor statement, mistyped EIGRP AS number, and so forth. You know the AS number has to match, but always double-check that. Next, check the wildcard mask to make sure the correct interfaces are EIGRP-enabled. In the following example, we've configured three loopbacks on R2 and want to advertise all three loopbacks via EIGRP, but R4 only sees one. - Cisco / Microsoft Computer Certification: Be Ready For Your Opportunity
I was reading The Big Moo: Stop Trying To Be Perfect and Start Being Remarkable this morning, and I’d recommend a copy of this to anyone who wants to improve their career and their future. And that’s all of us, right?
There was one particular line that really stood out to me: Betting on change is always the safest bet available. That describes life perfectly, but it also describes a career in Information Technology perfectly as well. There is no field in the world that has the constant and never-ending changes that IT does. And every single one of us can look at this as a massive opportunity for personal and professional growth. - Cisco Ccna / Ccnp Certification Exam: Troubleshooting Direct Serial Connections
A prime topic of your CCNA and CCNP CIT exams will be connecting Cisco routers directly via their Serial interfaces, and while the configuration is straightforward, there are some vital details and show commands you must know in order to pass the exams and configure this successfully in production and home lab networks. Let's take a look at a sample configuration.
Connecting Cisco routers directly via their Serial interfaces works really well once you get it running - and getting such a connection up and running is easy enough. You can use show controller serial x to find out which endpoint is acting as the DCE, and it's the DCE that must be configured with the clockrate command. - Cisco Ccna / Ccnp Certification Exam Lab: Frame Relay Subinterfaces And Split Horizon
Earning your Cisco CCNA and CCNP is a tough proposition, and part of that is the fact that you quickly learn that there’s usually more than one way to do things with Cisco routers – and while that’s generally a good thing, you better know the ins and outs of all options when it comes to test day and working on production networks. Working with Frame Relay subinterfaces and split horizon is just one such situation.
One reason for the use of subinterfaces is to circumvent the rule of split horizon. You recall from your CCNA studies that split horizon dictates that a route cannot be advertised out the same interface upon which it was learned in the first place. In the following example, R1 is the hub and R2 and R3 are the spokes. All three routers are using their physical interfaces for frame relay connectivity, and they are also running RIPv2 172.12.123.0 /24. Each router is also advertising a loopback interface, using the router number for each octet. - Cisco Ccna / Ccnp Certification Exam: Cabling Your Home Lab
More CCNA and CCNP candidates than ever before are putting together their own home labs, and there's no better way to learn about Cisco technologies than working with the real thing. Getting the routers and switches is just part of putting together a great CCNA / CCNP home lab, though. You've got to get the right cables to connect the devices, and this is an important part of your education as well. After all, without the right cables, client networks are going to have a hard time working!
For your Cisco home lab, one important cable is the DTE/DCE cable. These cables have two major uses in a home lab. To practice directly connecting Cisco routers via Serial interfaces (an important CCNA skill), you'll need to connect them with a DTE/DCE cable. Second, if you plan on having a Cisco router act as a frame relay switch in your lab, you'll need multiple DTE/DCE cables to do so. (Visit my website's Home Lab Help section for a sample Frame Relay switch configuration.) - Cisco Ccna / Ccnp Certification Exam: Caller Id Screening And Callback
As a CCNA and/or CCNP candidate, you've got to be able to spot situations where Cisco router features can save your client money and time. For example, if a spoke router is calling a hub router and the toll charges at the spoke site are higher than that of the hub router, having the hub router hang up initially and then call the spoke router back can save the client money (and make you look good!)
A popular method of doing this is using PPP callback, but as we all know, it's a good idea to know more than one way to do things in Cisco World! A lesser-known but still effective method of callback is Caller ID Screening & Callback. Before we look at the callback feature, though, we need to know what Caller ID Screening is in the first place! - Cisco Ccna / Ccnp Certification Exam: Same Command, Different Results
As a CCNA or CCNP, one thing you've got to get used to is that change is constant. Cisco regularly issues new IOS versions, not to mention the many different kinds of hardware they produce! While it's always nice to have "the latest and the greatest" when it comes to routers, switches, firewalls, etc., we have to be prepared for the fact that not all our clients are going to have that latest and greatest!
For instance, there are still quite a few Catalyst 5000 switches out there humming away, and if you're used to working on IOS-driven switches like the 2950, the same command can have dramatically different results. - Cisco Ccna / Ccnp Certification Exam: Frame Relay Encapsulation Types
When you're studying to pass the Cisco CCNA and CCNP certification exams, you quickly learn that there's always something else to learn. (You'll really pick up on this in your CCIE studies, trust me!) Today we'll take a look at an often-overlooked topic in Frame Relay, the encapsulation type. You don't exactly change this on a daily basis in production networks (not if you want to stay employed, anyway!), but it's an important exam topic that you must be familiar with.
The DCE and DTE must agree on the LMI type, but there's another value that must be agreed upon by the two DTEs serving as the endpoints of the VC. The Frame encapsulation can be left at the default of Cisco (which is Cisco-proprietary), or it can be changed to the industry-standard IETF, as shown below. If a non-Cisco router is the remote endpoint, IETF encapsulation must be used. Note that the default of Cisco isn't listed as an option by IOS Help, so you better know that one by heart! - Cisco Ccna / Ccnp Certification Exam: Frame Relay Becns And Fecns
BECNs and FECNs aren't just important to know for your Cisco CCNA and CCNP certification exams - they're an important part of detecting congestion on a Frame Relay network and allowing the network to dynamically adjust its transmission rate when congestion is encountered.
The Forward Explicit Congestion Notification (FECN, pronounced "feckon") bit is set to zero by default, and will be set to 1 if congestion was experienced by the frame in the direction in which the frame was traveling. A DCE (frame relay switch) will set this bit, and a DTE (router) will receive it, and see that congestion was encountered along the frame's path. - Cisco Ccna / Ccnp Exam Tutorial: Testing Isdn Links Without Pings
To earn your Cisco CCNA and CCNP certifications, you've got to master ISDN - and despite what some people say, there's still a lot of ISDN out there that needs to be supported. And when it comes to troubleshooting ISDN, there's a lot to look at. Is the correct ISDN switchtype configured? Are the dialer map statements correct? What about the dialer-group and dialer-list commands? And that's just the start.
I always say that all troubleshooting starts at Layer 1, the Physical layer of the OSI model. The usual method of troubleshooting ISDN is sending pings across the link, but the connection can be tested without using pings or even before assigning IP addresses to the BRI interfaces! - Cisco Ccna / Ccnp Certification Exam Tutorial: Floating Static Routes
To pass the Cisco CCNA and CCNP certification exams, as well as becoming a world-class networker, you've got to know how and when to use floating static routes. And if you're wondering what makes them "float" -- read on!
In this example, R1 and R2 are running OSPF over a Frame Relay network, 172.12.123.0 /24. They're also connected by a BRI ISDN link, 172.12.12.0 /24. R1 is advertising a loopback network, 1.1.1.1 /32, via OSPF. We want R2 to have a route to that loopback even if the frame goes down - and here, we'll use a floating static route to make that happen. - Cisco Ccna / Ccnp Certification Exam Tutorial: Configuring Ppp Callback
You may run into situations where a router in a remote location needs to dial in to a central router, but the toll charges are much higher if the remote router makes the call. This scenario is perfect for PPP Callback, where the callback client places a call to a callback server, authentication takes place, and the server then hangs up on the client! This ensures that the client isn't charged for the call. The server then calls the client back.
In the following example, R2 has been configured as the client and R1 is the callback server. Let's look at both configurations and the unique commands PPP Callback requires. - Cisco Ccna / Ccnp Certification Exam Tutorial: Dialer Watch
Dialer Watch is a vital part of your CCNA and CCNP studies, particularly for the BCRAN exam, but it's one of the most misunderstood technologies as well. To help you pass the CCNA and CCNP certification exams, here's a detailed look at Dialer Watch.
Dialer Watch allows you to configure a route or routes as "watched" when the watched route leaves the routing table and there is no other valid route to that specific destination, the ISDN link will come up. In the following example, R1 and R2 are connected by both a Frame Relay cloud over the 172.12.123.0 /24 network and an ISDN cloud using the 172.12.12.0 /24 network. The routers are running OSPF over the Frame cloud, and R1 is advertising its loopback of 1.1.1.1/32 as well as an Ethernet segment, 10.1.1.0/24, via OSPF. R2 has both of these routes in its OSPF table, as shown below. - Cisco Ccna / Ccnp Certification Tutorial: Frame Relay End-to-end Keepalives
One of the first things you learned about Frame is that the LMI also serves as a keepalive, or a heartbeat - and if three consecutive LMIs are missed, the line protocol goes down. There's a limitation to LMI as a keepalive, though. The LMI is exchanged only between the DTE and the closest DCE. The LMI is therefore a local keepalive that does not reflect any possible issues on the remote end of the virtual circuit.
Taking the LMI concept to the next logical level, Frame Relay End-To-End Keepalives (FREEK, one of the least-heard Cisco acronyms for some reason) are used to verify that endpoint-to-endpoint communications are functioning properly. - Cisco Ccna Certification Exam Tutorial: Port-based Authentication
To pass your CCNA exam and earn this coveted certification, you must understand the details of port-based authentication. This knowledge has a great deal of value in production networks as well, since this authentication scheme is regularly implemented. Let's take a look at this particular CCNA skill.
Consider a situation where you have a server that will be connected to your switch, and you want the port to shut down if a device with a different MAC address that that of the switch attempts to connect to that port. You could also have a situation where you have someone who has a connection to a switch port in his office, and he wants to make sure that only his laptop can use that port. - Cisco Ccna / Ccnp Certification Exam Review: Protocol Basics
To earn your Cisco CCNA certification and pass the BSCI CCNP exam, you have to know your protocol basics like the back of your hand! To help you review these important concepts, here's a quick look at the basics of RIPv1, RIPv2, IGRP, and EIGRP.
RIPv1: Broadcasts updates every 30 seconds to the address 255.255.255.255. RIPv1 is a classful protocol, and it does not recognize VLSM, nor does it carry subnet masking information in its routing updates. Update contains entire RIP routing table. Uses Bellman-Ford algorithm. Allows equal-cost load-balancing by default. Max hop count is 15. Does not support clear-text or MD5 authentication of routing updates. Updates carry 25 routes maximum. - Cisco Ccna / Ccnp Certification Exam Tutorial: Isdn And Multilink Ppp
ISDN is a huge topic on both your Cisco CCNA and BCRAN CCNP exams. While many ISDN topics seem straightforward, it’s the details that make the difference in the exam room and working with ISDN in production networks. Configuring and troubleshooting multilink PPP is just one of the skills you’ll need to pass both of these demanding exams.
With BRI, we've got two B-channels to carry data, and both of them have a 64-kbps capacity. You might think it would be a good idea to have both channels in operation before one reaches capacity, and it is a great idea Problem is, it's not a default behavior of ISDN. The second b-channel will not begin to carry traffic until the first one reaches capacity. - Cisco Ccnp / Bsci Exam Tutorial: 10 Isis Details You Must Know!
Earning your CCNP certification and passing the BSCI exam depends on knowing the details of many Cisco technologies, ISIS chief among them. To help you prepare for exam success, here's a list of ISIS terminology and basic concepts that will help you pass this tough exam. Enjoy!
ISIS Terms: - Cisco Ccna / Ccnp / Bcmsn Exam Review: Trunking And Trunking Protocols
To earn your CCNA or CCNP certification, you've got to understand the basics of trunking. This isn't just a CCNA topic - you must have an advanced understanding of trunking and etherchannels to pass the BCMSN exam and earn your CCNP as well. Before we address those advanced topics, though, you need to master the fundamentals!
A trunk allows inter-VLAN traffic to flow between directly connected switches. By default, a trunk port is a member of all VLANs, so traffic for any and all VLANs can travel across this trunk. That includes broadcast traffic! - Ccna / Mcse / Ccnp Certification: Making Failure Work For You
Whether you're on the road to the CCNA, CCNP, MCSE, or you're on any other computer certification track, the odds are that sooner or later, you're going to fail an exam. It's happened to almost all of us, yours truly included. What you have to keep in mind in these times is that success is not a straight line. You've probably seen charts showing the growth of an industry or a business -- you know, the ones that go from left to right, and look kind of jagged. The line goes up for a while, then down a bit, then up some more, then down a little.
The key? While every business has its setbacks, the net result is that the line goes up and progress is made. That's how you want your certification pursuit and your career to go as well - upward! - Ccnp Certification / Bcmsn Exam Tutorial: Server Load Balancing (slb)
When you're working on your BCMSN exam on your way to CCNP certification, you'll read at length about how Cisco routers and multilayer switches can work to provide router redundancy - but there's another helpful service, Server Load Balancing, that does the same for servers. While HSRP, VRRP, and CLBP all represent multiple physical routers to hosts as a single virtual router, SLB represents multiple physical servers to hosts as a single virtual server.
In the following example, three physical servers have been placed into the SRB group ServFarm. They're represented to the hosts as the virtual server 210.1.1.14. - Ccnp Certification / Bsci Exam Tutorial: The Bgp Neighbor Process
Like TCP, BGP is connection-oriented. An underlying connection between two BGP speakers is established before any routing information is exchanged. This connection takes place on TCP port 179. As with EIGRP and OSPF, keepalive messages are sent out by the BGP speakers in order to keep this relationship alive.
Once the connection is established, the BGP speakers exchange routes and synchronize their tables. After this initial exchange, a BGP speaker will only send further updates upon a change in the network topology. - Cisco Ccna Certification Exam Tutorial: Keep Your Most Important Appointment
Imagine this. You have an appointment with a client to work on a server or router install. A few minutes before you're scheduled to be there, you decide there's something really good on TV you'd like to watch. Or you decide to go to the gym, or play a game, or do anything else except go see the client.
Even if you weren't going to get fired for not showing up, it's certainly unfair to the client. You've got a professional obligation, and you should be there on time.
Now, what's this got to do with you becoming a CCNA or CCNP? Plenty. Because when it comes to your study time, you're the client. You owe it to yourself to show up. You would never blow off an appointment to meet a client to get some important work done. - Cisco Ccna Certification Exam Tutorial: Distance Vector Command Review
Part of studying for CCNA exam success is keeping all these new commands straight in your head! And let's face it, there are a lot of commands you need to know in order to pass the CCNA exam and earn that certification. Here's a review of some very important distance vector and static routing commands you need to know, along with their proper usage and console output.
Bandwidth
IGRP makes a default assumption that any Serial interface running IGRP is connected to a T1 line, which runs at 1544 KBPS. With equal-cost load-balancing enabled by default, this may be an undesirable assumption. - Cisco Ccnp Certification / Bsci Exam Tutorial: An Introduction To Bgp
When you're studying for the BSCI exam on the way to earning your CCNP certification, it's safe to say that BGP is like nothing you’ve studied to this point. BGP is an external routing protocol used primarily by Internet Service Providers (ISPs). Unless you work for an ISP today or in the future, you may have little or no prior exposure to BGP. Understanding BGP is a great addition to your skill set – and you have to know the basics well to pass the BSCI exam.
Note that I said “the basics”. BGP is a very complex protocol, and when you pursue your CCIE, you’ll see what I’m talking about. As with all things Cisco, though, when broken down into smaller pieces, BGP becomes quite understandable. You will need to know the basics of BGP as presented in this chapter to pass your BSCI exam – so let’s get started. - Cisco Ccnp Certification / Bcmsn Exam Tutorial: The Hsrp Mac Address
To pass the BCMSN exam and earn your CCNP, you've got to know HSRP inside and out! Part of that is knowing how the MAC address of the virtual router is derived, and another part is knowing how to change this address. We'll look at both features in this tutorial.
We've got two routers on a segment running HSRP, so first we need to find out what the MAC address of the HSRP virtual router is. The show command for HSRP is show standby, and it's the first command you should run while configuring and troubleshooting HSRP. Let's run it on both routers and compare results. - Cisco Ccnp / Bcmsn Exam Tutorial: Changing The Active Router In Hsrp
To pass the BCMSN exam and earn your CCNP certification, you've got to know HSRP inside and out. While the operation and basic commands of HSRP are pretty simple, there are some important details that are easily overlooked but are vital in getting HSRP to work the way you want it to. Let's take a look at using the priority command correctly on both the exam and in production networks.
A key value in the show standby command is the priority. The default is 100, and the router with the highest priority will be the primary HSRP router. We'll raise the default priority on R2 and see the results. R3 is currently the Active router and R2 the standby, so let's raise the priority on R2 and see what happens. - Cisco Ccnp / Bsci Exam Tutorial: Ten Ip Routing Details You Must Know!
To pass the BSCI exam and earn your CCNP, you've got to keep a lot of details in mind. It's easy to overlook the "simpler" protocols and services such as static routing and distance vector protocols. With this in mind, here's a quick review of some details you should know for success in the exam room and real-world networks!
When packets need to be routed, the routing table is parsed for the longest prefix match if multiple paths exist with the same prefix length, the route with the lowest AD is preferred. If there are still multiple valid paths, equal-cost load-sharing goes into effect. - Cisco Ccna Certification Exam Tutorial: Configuring And Troubleshooting Vtp
Not only is your CCNA exam going to have questions on VLAN trunking protocol, almost any network that has more than one VLAN is going to have VTP running. Whether you're planning on passing the CCNA exam or just brushing up on your networking skills, this VTP tutorial will help you learn the basics of this important protocol.
VTP allows switches to advertise VLAN information between other members of the same VTP domain. VTP allows a consistent view of the switched network across all switches. When a VLAN is created on one switch in a VTP server, all other VTP devices in the domain are notified of that VLAN’s existence. VTP servers will know about every VLAN, even VLANs that have no members on that switch. - Ccna Certification Exam Tutorial: Cisco Switching Modes
To pass the CCNA exam and earn this important certification, you’ve got to know switching inside and out. While you’re learning all the basic switching theory, make sure to spend some time with the one of three switching modes Cisco routers can use.
Store-and-Forward is exactly what it sounds like. The entire frame will be stored before it is forwarded. This mode allows for the greatest amount of error checking, since a CRC (Cyclical Redundancy Check) is run against the frame before it is forwarded. If the frame contains an error, it is discarded. If there’s no problem with the frame, the frame is then forwarded to its proper destination. - Ccnp / Bsci Exam Tutorial: Route Summarization And The Ospf Null Interface
CCNP exam success, particularly on the BSCI exam, demands you understand the details of route summarization. This skill not only requires that you have a comfort level with binary conversions, but you have to know how and where to apply route summarization with each individual protocol.
You also have to know the "side effects" of route summarization. With OSPF, there will actually be an extra interface created at the point of summarization, and this catches a lot of CCNP candidates by surprise. Let's take a look at the null0 interface and how it relates to OSPF summarization. - `Ccnp Certification / Bcmsn Exam Tutorial: Hsrp Mac Addresses And Timers
To earn your CCNP certification and pass the BCMSN exam, you've got to know what HSRP does and the many configurable options. While the operation of HSRP is quite simple (and covered in a previous tutorial), you also need to know how HSRP arrives at the MAC address for the virtual router - as well as how to configure a new MAC for this virtual router. This puts us in the unusual position of creating a physical address for a router that doesn't exist!
The output of show standby for a two-router HSRP configuration is shown below. - Cisco Ccna Certification Exam Tutorial: Access List Details You Must Know!
To pass the CCNA exam, you have to be able to write and troubleshoot access lists. As you climb the ladder toward the CCNP and CCIE, you'll see more and more uses for ACLs. Therefore, you had better know the basics!
The use of "host" and "any" confuses some newcomers to ACLs, so let's take a look at that first. - Ccnp Certification / Bsci Exam Tutorial: Eigrp Stuck-in-active Routes
Passing the BSCI exam and earning your CCNP is all about knowing the details, and when it comes to EIGRP SIA routes, there are plenty of details to know. A quick check in a search engine for "troubleshoot SIA" will bring up quite a few matches. Troubleshooting SIA routes is very challengin in that there's no one reason they occur.
View the EIGRP topology table with the show ip eigrp topology command, and you'll see a code next to every successor and feasible successor. A popular misconception is that we want these routes to have an "A" next to them - so they're active. That's what we want, right? Active routes sound good, right? - Ccnp Certification / Bcmsn Exam Tutorial: Getting Started With Hsrp
Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in which routers are put into an HSRP router group. Along with dynamic routing protocols and STP, HSRP is considered a high-availability network service, since all three have an almost immediate cutover to a secondary path when the primary path is unavailable.
One of the routers will be selected as the primary ("Active", in HSRP terminology), and that primary will handle the routing while the other routers are in standby, ready to handle the load if the primary router becomes unavailable. In this fashion, HSRP ensures a high network uptime, since it routes IP traffic without relying on a single router. - Ccnp Certification / Bcmsn Exam Tutorial: Qos Service Types
To pass the CCNP exams, you’ve got to master Quality of Service, and the first step in doing so is knowing the differences between the different QoS types.
Now this being Cisco, we can't just have one kind of QoS! We've got best-effort delivery, Integrated Services, and Differentiated Services. Let's take a quick look at all three. - Cisco Ccna Certification Exam Tutorial: Configuring Dialer Profiles
The most common method of configuring ISDN is with dialer maps, but dial information can also be configured on a logical interface. To pass the CCNA exam, you must know how to configure and troubleshoot both dialer maps and dialer profiles.
Dialer Profiles allow different dialing information to be configured onto logical interfaces. The logical interfaces may have different dialing destinations, different remote router names, etc., but they’ll be using the same physical interface. - Cisco Ccnp Certification / Bcmsn Exam Tutorial: Writing Qos Policy
QoS - Quality of Service - is a huge topic on both the BCMSN exam and real-world networks. QoS is so big today that Cisco's created separate specialist certifications that cover nothing but QoS! It can be an overwhelming topic at first, but master the fundamentals and you're on your way to exam and job success.
If you work with QoS at any level - and sooner or later, you will - you've got to know how to write and apply QoS policies. - Cisco Ccnp Certification / Bsci Exam Tutorial: Comparing Irdp And Hsrp
To pass the BSCI exam, you need to know the difference between IRDP and HSRP. While they have the same basic function, the operation and configuration of each are totally different.
The aim of both is to allow hosts to quickly discover a standby router when the primary router fails. IRDP is commonly used by Windows DHCP clients and several Unix variations, but you do see it in Cisco routers as well. IRDP is defined in RFC 1256. - Cisco Ccna Certification Exam Tutorial: Frame Relay Dlcis And Mappings
Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we're going to examine what DLCIs do and how they're mapped on a Cisco router.
Frame Relay VCs use Data-Link Connection Identifiers (DLCI - pronounced "del-see") as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination. - Cisco Ccnp / Bcsi Exam Tutorial: Broadcasts And The Ip Helper-address Command
While routers accept and generate broadcasts, they do not forward them. This can be quite a problem when a broadcast needs to get to a device such as a DHCP or TFTP server that's on one side of a router with other subnets on the other side.
If a PC attempts to locate a DNS server with a broadcast, the broadcast will be stopped by the router and will never get to the DNS server. By configuring the ip helper-address command on the router, UDP broadcasts such as this will be translated into a unicast by the router, making the communication possible. The command should be configured on the interface that will be receiving the broadcasts. - Cisco Ccnp / Bcmsn Exam Tutorial: Switches, Qos, And Cisco's Networking Model
QoS is a big topic on your BCMSN and CCNP exams, and for good reason. As more and more traffic flows through today's networks, accurately applying QoS to both your routers and switches becomes more important.
Note the phrase "accurately applying". You must have a plan in place before you start configuring QoS on your switches, and to create such a plan you should use Cisco's Three-layer Hierarchical Model. - Cisco Ccna / Ccnp Home Lab Tutorial: The 2501 Router
To be truly prepared for your CCNA and CCNP exams, you need real hands-on experience with real Cisco routers and switches. However, a production network is a really bad place to practice your configurations, but an excellent way to get fired and/or sued. The key to becoming a true CCNA and CCNP is assembling your own Cisco home lab.
You don't have to spend a lot of money to do so; used Cisco equipment is cheaper than ever. It's robust as well - I've bought literally hundreds of used routers and switches over the years and have had very few problems. I owe much of my skill to practicing configurations and troubleshooting in my own home lab. - Cisco Ccnp / Bcmsn Exam Tutorial: Configuring Cgmp On Routers & Switches
If a Layer Two switch doesn't have the capabilities to run IGMP Snooping, it will be able to run CGMP - Cisco Group Membership Protocol. CGMP allows the multicast router to work with the Layer Two switch to eliminate unnecessary multicast forwarding.
CGMP will be enabled on both the multicast router and the switch, but the router's going to do all the work. The router will be sending Join and Leave messages to the switch as needed. PIM must be running on the router interface facing the switch before enabling CGMP, as you can see: - Cisco Ccna Certification Exam Tutorial: Isdn Details You Must Know
CCNA exam success depends partially on knowing the details of ISDN, and there are plenty of them! To help you review for your CCNA exam, here are a few ISDN details that you must know on exam day. (They help in the real world, too – and there are still plenty of ISDN networks out there!
The Cisco-proprietary version of HDLC is the default encapsulation type for serial and ISDN interfaces. - Cisco Ccna / Ccnp Home Lab Tutorial: The 2503 Router
I know from experience that part of the excitement and anxiety of putting together your own CCNA / CCNP home lab is deciding what to buy! While you can make a workable home lab out of almost any combination of Cisco routers and switches, some routers are better suited for home lab work than others because they can fill multiple roles.
When you buy CCNA or CCNP "lab kits" - bundles of routers and switches - you can get a little confused about whether you're getting a good deal. One router I get asked about quite a bit is the 2503. - Cisco Ccnp / Bcmsn Exam Tutorial: Multicasting And The Rpf Check
Multicasting is a vital topic on your BCMSN, CCNP, and CCIE exams, and it can also be very confusing when you first start studying it. Multicasting uses concepts that are unlike anything you've run into in your routing protocol studies, and that can throw you at first. I speak from experience that multicasting is like any other Cisco technology - learn the basics, master the fundamentals, and then build your skills on that foundation.
One such fundamental is the RPF Check, or Reverse Path Forwarding Check. - Cisco Ccna Certification Exam Tutorial: Variance And Unequal Cost Load Balancing
To pass the CCNA exam, you've got to know how to work with IGRP and EIGRP unequal-cost load balancing. You may not see much IGRP in production networks anymore, but you'll see a lot of EIGRP, and part of fine-tuning your EIGRP network is making sure that all paths are in use while allowing for varying bandwidth rates.
Using the variance command is the easy part - it's getting the metric that's the hard part with IGRP. With EIGRP, you just look in the topology table and that's it. With IGRP, you've got to run a debug to get the right metric. - Cisco Ccnp / Bcmsn Exam Tutorial: Multicasting And Reserved Addresses
Ever since you picked up your first CCNA book, you've heard about multicasting, gotten a fair idea of what it is, and you've memorized a couple of reserved multicasting addresses. Now as you prepare to pass the BCMSN exam and become a CCNP, you've got to take that knowledge to the next level and gain a true understanding of multicasting. Those of you with an eye on the CCIE will truly have to become multicasting experts!
Having said that, we're going to briefly review the basics of multicasting first, and then future tutorials will look at the different ways in which multicasting can be configured on Cisco routers and switches. - Cisco Ccnp / Bsci Exam Tutorial: Ospf Route Redistribution Review
OSPF route redistribution is an important topic on the BSCI exam, and it's a topic full of details and defaults that you need to know for the exam room and the job. To help you pass the BSCI exam, here's a quick review of some of the OSPF route redistribution basics.
To see if a router is an ABR or ASBR, run show ip ospf. This also displays any routes being redistributed into OSPF on this router.
|
|
|
