Cisco CCNA / CCNP Exam Tutorial: EIGRP Dual Queries, SIA, And Stub Routers

EIGRP is a major subject of the CCNA exam, and Cisco goes into even more detail with EIGRP on your CCNP exams. Part of that detail is the purpose and configuration of EIGRP stub routers.

A problem with EIGRP comes in when a successor is lost and there is no feasible successor. DUAL doesn't give up that easily, though. DUAL will mark the route as Active, indicating that the route is being calculated and cannot be used to route data, and will send out a Query message.

A DUAL Query is basically one neighbor asking another, "Hey, do you know how to get to this network I just lost my route to?" If that neighbor has a route, the query will be answered with that route; if the neighbor doesn't have such a route, that neighbor will ask its neighbors. The process continues until a downstream router replies with the desired route, or the EIGRP downstream routers run out of neighbors to ask.

It's a good idea to limit the scope of your DUAL queries, otherwise routes may go into Stuck In Active state during this reconfiguration. Route summarization helps to limit queries, as does configuration of EIGRP stub routers.

While EIGRP does not have the stub area options that OSPF does, EIGRP does allow a router to be configured as stub. This is commonly done with a hub-and-spoke configuration where the spoke routers do not have the resources to keep a full routing table. Since the spoke's next hop will always be the hub, all the spoke really needs is a default route. For this reason, the only neighbor an EIGRP stub router can have is the hub router. (Obviously, the hub would never be configured as stub.)

Configuring EIGRP stub routers also combats the SIA problem. EIGRP stub routers are not queried for routes when the hub does not have a feasible successor for a successor route that has gone down.

By default, EIGRP stub routers advertise information about two types of routes back to the hub - directly connected networks and summary routes. To change this default, use the eigrp stub command followed by the types of routes you want the stub to advertise back to the hub. (The eigrp stub command run by itself configures the router as stub.)

R1(config)#router eigrp 100

R1(config-router)#eigrp stub ?

connected Do advertise connected routes

receive-only Set IP-EIGRP as receive only neighbor

static Do advertise static routes

summary Do advertise summary routes

Assume a network where R5 is the hub and R4, R6, and R7 are spokes. As long as the spokes have a neighbor relationship only with the hub, they can be configured as stub routers. They will then advertise their directly connected networks and summary routes back to the hub and will receive only a default route back from the hub. If R5 loses a successor and has no feasible successor, it will not send a query packet to any of the stub routers.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage , home of free CCNA and CCNP tutorials! Pass the CCNA exam with Chris Bryant!

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.

R2#show standby

Ethernet0 - Group 5

Local state is Standby, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 0.776

Virtual IP address is 172.12.23.10 configured

Active router is 172.12.23.3, priority 100 expires in 9.568

Standby router is local

1 state changes, last state change 00:00:22

R3#show standby

Ethernet0 - Group 5

Local state is Active, priority 100

Hellotime 3 sec, holdtime 10 sec

Next hello sent in 2.592

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.2 expires in 8.020

Virtual mac address is 0000.0c07.ac05

2 state changes, last state change 00:02:08

R3 is in Active state, while R2 is in Standby. The hosts are using the 172.12.123.10 address as their gateway, but R3 is actually handling the workload. R2 will take over if R3 becomes unavailable.

An IP address was statically assigned to the virtual router, but not a MAC address. However, there is a MAC address under the show standby output on R3, the active router. How did the HSRP process arrive at a MAC of 00-00-0c-07-ac-05?

Well, most of the work is already done before the configuration is even begun. The MAC address 00-00-0c-07-ac-xx is reserved for HSRP, and xx is the group number in hexadecimal. That's a good skill to have for the exam, so make sure you're comfortable with hex conversions. The group number is 5, which is expressed as 05 with a two-bit hex character. If the group number had been 17, we'd see 11 at the end of the MAC address - one unit of 16, one unit of 1.

On rare occasions, you may have to change the MAC address assigned to the virtual router. This is done with the standby mac-address command. Just make sure you're not duplicating a MAC address that's already on your network!

R2(config-if)#standby 5 mac-address 0000.1111.2222

1d12h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Active -> Learn

R2#show standby

Ethernet0 - Group 5

Local state is Active, priority 150, may preempt

Hellotime 4 sec, holdtime 12 sec

Next hello sent in 3.476

Virtual IP address is 172.12.23.10 configured

Active router is local

Standby router is 172.12.23.3 expires in 10.204

Virtual mac address is 0000.1111.2222 configured

4 state changes, last state change 00:00:00

1d12h: %STANDBY-6-STATECHANGE: Ethernet0 Group 5 state Listen -> Active

The MAC address will take a few seconds to change, and the HSRP routers will go into Learn state for that time period.

A real-world HSRP troubleshooting note: If you see constant state changes with your HSRP configuration, do what you should always do when troubleshooting - check the physical layer first. Best of luck on your BCMSN exam!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage , home of free CCNA and CCNP tutorials! Pass the CCNA exam with Chris Bryant

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.

Switches run VTP in one of three modes. In server mode, VLANs can be created, modified, and deleted on a VTP server. When these actions are taken, the changes are advertised to all switches in the VTP domain. VTP Servers keep VLAN configuration information upon reboot.

In client mode, the switch cannot modify, create, or delete VLANs. VTP clients cannot retain VLAN configuration information upon reboot; they have to obtain this information from a VTP server.

In real-world networks, this is generally done to centralize the creation and deletion of VLANs. An interesting side effect of the server/client methodology is that if a VLAN is only to have ports on the VTP client switch, the VLAN must still first be created on the VTP server. The VTP client will learn about the VLAN from the VTP server, and ports can then be placed into that VLAN.

The third VTP mode is transparent mode. VTP switches in this mode ignore VTP messages. They do forward the VTP advertisements received from other switches. VLANs can be created, deleted, and modified on a transparent server, but those changes are not advertised to the other switches in the VTP domain.

For switches running VTP to successfully exchange VLAN information, three things have to happen. I've listed them for you in the order that you'll see them in the real world.

The VTP domain name must match. This is case-sensitive. "CISCO" and "cisco" are two different domains.

To distribute information about a newly-created VLAN, the switch upon which that VLAN is created must be in Server mode.

Learning VTP isn't just a good idea for passing your CCNA exams, it's a skill you must have to be effective in configuring and troubleshooting VLANs. I wish you the best in both of these pursuits!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.

You can also join his RSS feed and visit his blog, which is updated several times daily with new Cisco certification articles, free tutorials, and daily CCN

Cisco CCNP / BCMSN Exam Tutorial: BPDU Skew Detection

You may look at that feature's name and think, "What is a BPDU Skew, and why do I want to detect it?" What we're actually attempting to detect are BPDUs that aren't being relayed as quickly as they should be.

After the root bridge election, the root bridge transmits BPDUs, and the non-root switches relay that BPDU down the STP tree. This should happen quickly all around, since the root bridge will be sending a BPDU every two seconds by default ("hello time"), and the switches should relay the BDPUs fast enough so every switch is seeing a BPDU every two seconds.

That's in a perfect world, though, and there are plenty of imperfect networks out there! You may have a busy switch that can't spare the CPU to relay the BDPU quickly, or a BPDU may just simply be lost in transmission. That two-second hello time value doesn't give the switches much leeway, but we don't want the STP topology recalculated unnecessarily either.

BDPU Skew Detection is strictly a notification feature. Skew Detection will not take action to prevent STP recalculation when BDPUs are not being relayed quickly enough by the switches, but it will send a syslog message informing the network administrator of the problem. The amount of time between when the BDPU should have arrived and when it did arrive is referred to as "skew time" or "BPDU latency".

A busy CPU could quickly find itself overwhelmed if it had to send a syslog message for every BPDU delivery that's skewed. The syslog messages will be limited to one every 60 seconds, unless the "skew time" is at a critical level. In that case, the syslog message will be sent immediately with no one-per-minute limit.

And what is "critical", according to BDPU Skew Detection? Any value greater than 1/2 of the MaxAge value, making the critical skew time level 10 seconds or greater.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Pass your CCNP exam with The Bryant Advantage

Cisco CCNA / CCNP Home Lab Tutorial: Using 2520 Routers

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.

My personal favorite is the Cisco 2520. This router has four serial interfaces, making it an ideal frame relay switch. Don't forget that just because you're using a router as a frame switch, you can still use its routing capabilities. One setup I use is to use three of the four serial interfaces for frame switching and the fourth interface as a point-to-point network with another router. All you need is some DTE/DCE cables and you're all set.

The 2520 also comes with one ethernet interface and an ISDN interface, so that gives you even more options. Even if you're not planning to run ISDN in your home lab right now, you may choose to do so in the future - and with a 2520, you've already got the right router to do so. Keep in mind that if you are going to run ISDN in your home lab, you'll need an ISDN device such as an ISDN simulator in your lab. (ISDN simulators are physical devices and are plentiful on ebay - they're no relation to "router simulators".)

Again, I want to reiterate that you can work any Cisco router into a CCNA / CCNP home lab - there's no "right" or "wrong" combination of equipment. But as with anything else, some combinations are better than others, so consider adding some 2520s to your home lab! This router gives you a great combination of interfaces and capabilities, plus the most important factor of all - real hands-on experience during your CCNA and CCNP exam preparation!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Get your CCNA study guide from The Bryant Advantage!

Cisco / MCSE Exam Study: Creating A Road Map To Success

Planning for success on the CCNA, CCNP, and other Cisco exams is much like taking a trip in your car. You've got to plan ahead, accept the occasional detour, and just keep on going until you get there. But what do you do before you get started?

Create a road map - for success.

If you were driving from one side of the country to another, you certainly wouldn't just get in your car and start driving, would you? No. You would plan the trip out ahead of time. What would happen if you just got in the car and started driving in the hope that you would someday arrive at your final destination? You would never get there, and you'd spend a lot of time wandering aimlessly.

Don't spend your study time and slow your progress by studying for a Cisco exam without planning the trip. Schedule your study time as you would an appointment with a client, and keep that appointment. Make sure that your study time is quality study - turn your TV, iPod, and cell off. If you hit a bump in the road and don't get your certification the first time you take the exam, regroup and create another plan. Study until you get to the point that on exam day, you know that you are already a CCNA or CCNP and you're just there at the testing center to make it official.

The journey to success is not a straight line. When you look at a chart that shows a company's financial progress, the line never goes straight up. there are some ups and downs, but the overall result is success. The path to your eventual career and certification exam success may not be a direct one, but the important part is to get started - and to get any journey started, you've got to create a road map for a successful arrival at your destination.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNP and CCNA tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Pass your CCNP exam with The Bryant Advantage!

Cisco CCNP / BSCI Tutorial: Comparing OSPF And ISIS Hellos

While studying to pass the BSCI exam and preparing to earn your CCNP certification, you'll quickly notice that while OSPF and ISIS are both link-state protocols, there are a lot of differences between the two. One major difference is the way the two protocols handle hello packets.

Hello packets are imperative to keeping OSPF and ISIS adjacencies alive. Since they are both link-state protocols, neither of them will send updates at any specified time. Hello packets are the only method by which routers running OSPF and ISIS can see that a neighboring router is still available.

OSPF gives us some great options when it comes to keeping routing table size down via the use of stub and total stub areas, but to OSPF, a hello packet is a hello packet. ISIS routers are capable of sending two different types of hellos - Level 1 and Level 2.

ISIS routers are classified as Level 1 (L1), Level 2 (L2), and Level 1-2 (L1-L2). By default, Cisco routers are L1-L2 routers; this means that every ISIS-enabled interface will send out both L1 and L2 hellos.

If one of the interfaces is forming only an L1 or L2 adjacency, there's no reason to send out hellos for the other adjacency type. For example, if R1 is forming an L1 adjacency with R2 via its ethernet0 interface, there is no reason to allow the router to transmit L2 hellos. To hardcode a router interface to send only L1 or L2 hellos, use the isis circuit-type command.

R1(config)#interface ethernet0

R1(config-if)#isis circuit-type level-1

Note: To configure this interface to send only L2 hellos, the full command is "isis circuit-type level-2-only", not just "level-2".

This configuration would prevent L2 hellos from being transmitted out ethernet0. While this does save router resources and prevents unnecessary bandwidth usage, there is also no way an L2 adjacency can be formed - so double-check your network topology before using this command!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Earn your CCNA certification with The Bryant Advantage!

Cisco CCNA Certification: The Value Of The CCNA And CCNP

One question I see often on the 'Net is "Is it worth my time to earn a CCNA / CCNP / CCIE certification?" My personal answer to that is a resounding yes. The power of Cisco certifications has allowed me to create a tremendous career, and they can do the same for you.

There has never been a better time to accelerate your IT career, and earning a technical certification is a great way to do just that. I don't care if you're looking at earning an MCSE, a Cisco certification, Red Hat, or any other vendor - you are always better off having a technical certification than not having one. Technical certifications are an excellent way to market yourself and stand out from the crowd. Earning certifications shows a potential employer (and your current one) that you are willing to go the extra mile.

Sadly, when you ask this question on most Internet message boards, you're going to get some very negative people giving you their "unbiased" opinion. Ask yourself this question: Do you want to entrust the direction of your career to someone you don't know, has no accountability for what they say, and has some kind of ax to grind? Do you want someone like that to decide whether you should earn a CCNA or CCNP?

I can speak from experience on this point. When I told a few people that I was going to earn my CCIE, almost 100% of the responses I got were negative. "It's too hard", "no one can pass that", "the CCIE isn't worth the work", etc. Every single one of these statements is false, and again I speak from firsthand experience. The same is true for the CCNA, CCNP, and MCSE. All of these certifications can add value to your career and put more money in your pocket. But you have to make the decision to earn them and to "keep your goals away from the trolls".

Don't ask anonymous strangers whether it's "worth the time" to get a CCNA, MCSE, or other computer certification. The only person you should ask that question of is yourself. Whether you want to start an IT career or jumpstart your current one, make the decision to move forward in your career - and then follow through on that decision.

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials! For my FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies. Earn your CCNA certification with The Bryant Advantage!

What To Expect At The Cisco Testing Center

What To Expect At The Cisco Testing Center

 by: www.SemSim.com

Candidates can register for the CCNA exam (640-801 exam or 640-821 INTRO or 640-811 ICND ) at Pearson VUE or Prometric testing centers.

In order to do their best, candidates should know what to expect at the testing center for the Cisco CCNA certification exam. Since testing center guidelines may vary from one center to another, we recommend that the candidates call the local testing center to check about the guidelines. Here are some points providing information on what you can expect at the exam center:

Re-certification: If you have taken a Cisco CCNA certification exam before, find out your Cisco ID and specify it before you start with your registration. This will ensure that you get proper credit for the exam and will help avoid any duplicate records.

Reach before time: We strongly suggest reaching the test center before time. Failure to do so may result in cancellation of the appointment.

Sign the logbook: You may be asked to sign-in the logbook upon arrival as well as upon departure. Do check on this.

You must carry your identification: You will be required to show a valid identification (ID), perhaps including a recent, recognizable photograph. If the supervisor questions your ID, you may be required to show another ID. You should check the testing center guidelines on identification and take all supplemental identification documents with you.

Generally Accepted Identification:

Passport

Photobearing driver's license with signature

National/Military identification card

The following MAY not be accepted as valid ID:

Credit Cards (Please check with test center)

Private identification cards

Any expired ID

Read the testing center regulation form carefully: You will be provided with a Testing Center Regulation form by the supervisor. Read the regulations carefully and comply with them during the test.

Sign the confidentiality statement: The supervisor is responsible for asking you to sign the confidentially statement at the test center indicating that you will not reveal exam questions to other students after the test.

Supervisor sets up your test computer: The supervisor will ensure that the Cisco certification test displays on screen before handing over the machine to you.

Ask for sheets for scratch work: Scratch papers will be provided to you at the testing center. These are sometimes only available on request. Ask for some blank scratch sheets to do calculations and rough work. Jot down important points and tables (such as powers of 2, binary representation tables etc) before exam starts. This can be a big time saver. Do not take the scratch paper out of the testing room on completion of exam.

Items not allowed in the testing room: The candidate is not allowed to bring in the testing room personal items such as:

Books, revision sheets or notes: The exam is closed book

Cellular phones & alarms

Food or drinks may not be allowed

Calculators

Your session may be audio and video taped: Do not attempt to talk or communicate in any form to anybody in the testing room. Your session may be taped and can lead to immediate disqualification .

On exam completion: You will be explained by the supervisor what to do when you complete the exam. If not, or if you are unclear about what you should do, ask it yourself before beginning the exam.

Do not take with you the the testing material from the testing room: Return all of your testing materials, including the scrap paper, on the completion of your exam to the supervisor.

Certified copy of the exam result: Your supervisor will give you a certified copy of the exam report on completion of the test. This will list your score indicating strengths and weaknesses in the various test areas. Ask the supervisor for the certified copy, if you do not get it.

SemSim.com provides training resources for Cisco certification exams: CCIE, CCNP, CCNA, CCDP, CCDA. It offers FREE learning resources to students such as study guides and router simulation labs. For more information visit: http://www.SemSim.com : Making Cisco cetification easy! support@semsim.com

Cisco CCNA Certification: How And Why Switches Trunk

Your CCNA studies are going to include quite a bit of information about switches, and for good reason. if you don't understand basic switching theory, you can't configure and troubleshoot Cisco switches, either on the CCNA exam or in the real world. That goes double for trunking!

Trunking is simply enabling two or more switches to communicate and send frames to each other for transmission to remote hosts. There are two major trunking protocols that we need to know the details of for exam success and real-world success, but before we get to the protocols, let's discuss the cables we need.

Connecting two Cisco switches requires a crossover cable. As you know, there are eight wires inside an ethernet cable. In a crossover cable, four of the cables "cross over" from one pin to another. For many newer Cisco switches, all you need to do to create a trunk is connect the switches with a crossover cable. For instance, 2950 switches dynamically trunk once you connect them with the right cable. If you use the wrong cable, you'll be there a while!

There are two different trunking protocols in use on today's Cisco switches, ISL and IEEE 802.1Q, generally referred to as "dot1q". There are three main differences between the two. First, ISL is a Cisco-proprietary trunking protocol, where dot1q is the industry standard. (Those of you new to Cisco testing should get used to the phrases "Cisco-proprietary" and "industry standard".) If you're working in a multivendor environment, ISL may not be a good choice. And even though ISL is Cisco's own trunking protocol, some Cisco switches run only dot1q.

ISL also encapsulates the entire frame, increasing the network overhead. Dot1q only places a header on the frame, and in some circumstances, doesn't even do that. There is much less overhead with dot1q as compared to ISL. That leads to the third major difference, the way the protocols work with the native vlan.

The native vlan is simply the default vlan that switch ports are placed into if they are not expressly placed into another vlan. On Cisco switches, the native vlan is vlan 1. (This can be changed.) If dot1q is running, frames that are going to be sent across the trunk line don't even have a header placed on them; the remote switch will assume that any frame that has no header is destined for the native vlan.

The problem with ISL is that is doesn't understand what a native vlan is. Every single frame will be encapsulated, regardless of the vlan it's destined for.

Switching theory is a big part of your CCNA studies, and it can seem overwhelming at first. Just break your studies down into smaller, more manageable parts, and soon you'll see the magic letters "CCNA" behind your name!

Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com ), home of free CCNA and CCNP tutorials, and The Ultimate CCNA and CCNP Study Packages. For a copy of his FREE "How To Pass The CCNA" or "CCNP" ebook, visit the website and download your copies!