Cisco CCNP Certification / BCMSN Exam Tutorial: Uplinkfast
Posted on June 17th, 2010
You remember from your CCNA studies that when a port goes through the transition from blocking to forwarding, youre looking at a 50-second delay before that port can actually begin forwarding frames.
Configuring a port with PortFast is one way to get around that, but again, you can only use it when a single host device is found off the port. What if the device connected to a port is another switch?
A switch can be connected to two other switches, giving that local switch a redundant path to the root bridge, and thats great – we always want a backup plan! However, STP will only allow one path to be available, but if the available path to the root switch goes down, there will be a 50-second delay due to the STP timers MaxAge and ForwardDelay before the currently blocked path will be available.
The delay is there to prevent switching loops, and we cant use PortFast to shorten the delay since these are switches, not host devices. What we can use is Uplinkfast.
The ports that SW3 could potentially use to reach the root switch are collectively referred to as an uplink group. The uplink group includes the ports in forwarding and blocking mode. If the forwarding port in the uplink group sees that the link has gone down, another port in the uplink group will be transitioned from blocking to forwarding immediately. Uplinkfast is pretty much PortFast for wiring closets. (Cisco recommends that Uplinkfast not be used on switches in the distribution and core layers.)
Some additional details regarding Uplinkfast:
The actual transition from blocking to forwarding mode takes about three seconds.
Uplinkfast cannot be configured on a root switch.
Uplinkfast is configured globally. You cant run Uplinkfast on some ports or on a per-VLAN basis – its all or nothing.
The original root port will become the root port again when it detects that its link to the root switch has come back up. This does not take place immediately. The switch uses the following formula to determine how long to wait before transitioning back to the forwarding state:
( 2 x FwdDelay) + 5 seconds
Uplinkfast will take immediate action to ensure that the switch upon which it is configured cannot become the root switch. First, the switch priority will be set to 49,152, which means that if all other switches are still at their default priority, theyd all have to go down before this switch can possibly become the root switch. Additionally, the STP Port Cost will be increased by 3000, making it highly unlikely that this switch will be used to reach the root switch by any downstream switches.
And you just know theres got to be at least one option with this command, right? Lets run IOS Help and see.
SW2(config)#spanning-tree uplinkfast ?
max-update-rate Rate at which station address updates are sent
When there is a direct link failure, dummy multicast frames are sent to the MAC destination 0100.0ccd.cdcd. The max-update-rate value determines how many of these frames will be sent in a 100-millisecond time period.
Mastering the details of UplinkFast, BackboneFast, BPDU Guard, and Loop Guard are vital to your success on the CCNP exams, and one or more of these features are in use on almost every network in the world. Learn these features for success in both the exam room and the real world!
Tags: CCNA, CCNP
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Cisco Ccnp Certification Exam Tutorial: Knowing Radius And Tacacs+ For Your Iscw Exam
Posted on June 11th, 2010
As part οf yοur CCNP certificatiοn exam studies, particularly fοr the ISCW exam, yοu need tο be very clear οn the differences between TACACS+ and RADIUS.
As a CCNA and future CCNP, yοu’ve already cοnfigured authenticatiοn in the fοrm οf creating a lοcal database οf usernames and passwοrds fοr bοth Telnet access and PPP authenticatiοn. This is sοmetimes called a self-cοntained AAA deplοyment, since nο external server is invοlved.
It’s mοre than likely that yοu’ll be using a server cοnfigured fοr οne οf the fοllοwing security prοtοcοls:
TACACS+, a Ciscο-prοprietary, TCP-based prοtοcοl
RADIUS, an οpen-standard, UDP-based prοtοcοl οriginally develοped by the IETF
An οbviοus questiοn is “If there’s a TACACS+, what abοut TACACS?” TACACS was the οriginal versiοn οf this prοtοcοl and is rarely used tοday.
Befοre perfοrming AAA Authenticatiοn cοnfiguratiοn, there are sοme οther TACACS+ / RADIUS differences yοu shοuld be aware οf:
While TACACS+ encrypts the entire packet, RADIUS encrypts οnly the passwοrd in the initial client-server packet.
RADIUS actually cοmbines the authenticatiοn and authοrizatiοn prοcesses, making it very difficult tο run οne but nοt the οther.
TACACS+ cοnsiders Authenticatiοn, Authοrizatiοn, and Accοunting tο be separate prοcesses. This allοws anοther methοd οf authenticatiοn tο be used (Kerberοs, fοr example), while still using TACACS+ fοr authοrizatiοn and accοunting.
RADIUS dοes nοt suppοrt the Nοvell Async Services Interface (NASI) prοtοcοl, the NetBIOS Frame Prοtοcοl Cοntrοl prοtοcοl, X.25 Packet Assembler / Disassembler (PAD), οr the AppleTalk Remοte Access Prοtοcοl (ARA οr ARAP). TACACS+ suppοrts all οf these.
RADIUS implementatiοns frοm different vendοrs may nοt wοrk well tοgether, οr at all.
RADIUS can’t cοntrοl the authοrizatiοn level οf users, but TACACS+ can.
We’ll discuss the uses οf bοth οf these prοtοcοls in a future CCNP certificatiοn tutοrial! Lοοk fοr mοre CCNA, CCENT, and CCNP tutοrials right here οn this same website!
Tags: CCNA, CCNP
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Cisco CCNA / CCNP Certification Exam: Cabling Your Home Lab
Posted on June 9th, 2010
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.)
If you have multiple switches in your lab, that’s great, because you’ll be able to get a lot of spanning tree protocol (STP) work in as well as creating Etherchannels. To connect your switches, you’ll need crossover cables.
You’ll need some straight-through cables as well to connect your routers to the switches.
Finally, if you’re lucky enough to have an access server as part of your lab, you’ll need an octal cable to connect your AS to the other routers and switches in your lab. The octal cable has one large connector on one end and eight numbered RJ-45 connectors on the other end. The large connector should be attached to the async port on your AS, and the numbered RJ-45 connectors will be connected to the console ports on your other routers and switches.
Choosing and connecting the right cables for your Cisco CCNA / CCNP home lab is a great learning experience, and it’s also an important part of your Cisco education. After all, all great networks and home labs all begin at Layer One of the OSI model!
Tags: CCNA, CCNP, Cisco CCNA
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The Opportunities you will get with a Cisco CCNA Certification
Posted on May 28th, 2010
The following is a very good article I have read over at Buzzle.com. It talks about the various opportunities that a professional will acquire after passing the Cisco CCNA exam and obtaining this entry level certification.
Software industries are desperately in need of information technology professionals certified in the aspect of networking. You are almost guaranteed a job provided you possess an excellent working knowledge of protocols such as IP, IGRP, Serial, Frame Relay, IP RIP, and VLAN’s as well as installing, configuring, operating, maintaining, and trouble shooting LAN, WAN and other networks. One way to be sure you have such proper networking experience and knowledge is through obtaining your Cisco Certified Network Associate certification.
This CCNA certification is an entry level certification for all certified IT professionals who specialize in computer networking. This certification is just the first step towards even higher levels of training, such as Cisco Certified Network Professional or Cisco Certified Internet work Expert certification.
A CCNA certification is often the best option for field technicians, IT helps desk engineers, and other professionals of information technology based on overseeing the computer networking process. It is considered to be the basic qualification for installing, operating, configuring and troubleshooting a mid-sized switched and routed network. A professional with CCNA training is trusted to work with a networking environment which would include a group of switched networks. They can manage a host of computer routed networks connected through switches with the greatest of ease.
There is an ever increasing demand for networking specialists as businesses reliance on computers grow and with that the value of a CCNA certification is also finding itself to be a hot commodity among the information technology industry’s job market. It is a benchmark for discovering who are the best and the most efficient technicians are who aren’t in network management. Think of it as a way to filter out the cream of the crop from the rest.
The certification examination is structured around a set of questions with drag and drop options, multiple choice single answers, multiple choice multiple answers, simulations and fill in the blank type of questions. While at first glance, that may sound to be quite easy, to be truly successful and pass this test professional training is required. The examination is built so that your technical and special knowledge of computer networking environments and solutions are pushed to the limits. Basically, not everyone can pass this test.
In today’s ultra-competitive job market, you need every advantage you can to market yourself. You need something to make yourself more attractive to a business compared to another IT professional. A CCNA certification, accepted and recognized all over the world, is the perfect tool to do just that. The CCNA examination is used as a tool for sorting out the best networking professionals who would be responsible for the management and maintenance of the networking environments.
Tags: CCNA, CCNA certification
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CCNP ROUTE Portable Command Guide
Posted on May 27th, 2010
Review & Description
CCNP ROUTE Portable Command Guide
All the ROUTE 642-902 Commands in One Compact, Portable Resource
Scott Empson
Hans Roth
Preparing for the CCNP exam? Working as a network professional? Here are all the CCNP-level commands for the Implementing Cisco IP Routing (ROUTE) exam you need in one handy resource. The CCNP ROUTE Portable Command Guide is filled with valuable, easy-to-access information and is portable enough for use whether you’re in the server room or the equipment closet.
This book helps you memorize commands and concepts as you work to pass the CCNP ROUTE exam (642-901). The guide summarizes all CCNP certification-level Cisco IOS? Software commands, keywords, command arguments, and associated prompts, providing you with tips and examples of how to apply the commands to real-world scenarios. Configuration examples throughout the book provide you with a better understanding of how these commands are used in simple network designs.
Use CCNP ROUTE Portable Command Guide as a quick, offline resource for research and solutions.
–Logical “how-to” topic groupings inside the front and back covers provide one-stop research
–Compact size makes it easy to carry with you, wherever you go
–Helps you review important commands before taking the CCNP ROUTE certification exam
–“Create Your Own Journal” appendix with blank, lined pages enables you to personalize the book for your own needs
This book is part of the Cisco Press Certification Self-Study Product Family, which offers readers a self-paced study routine for Cisco certification exams. Titles in the Cisco Press Certification Self-Study Product Family are part of a recommended learning program from Cisco Systems that includes simulation and hands-on training from authorized Cisco Learning Partners and self-study products from Cisco Press.
Tags: 642-901, CCNP, CCNP exam, sco certification
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Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard
Posted on May 26th, 2010
In your CCNA studies, you learned about PortFast and the trouble it can cause if configured on the wrong port! Suitable only for switch ports connected directly to a single host, PortFast allows a port running STP to go directly from blocking to forwarding mode.
A Cisco router will give you a warning when you configure PortFast:
SW1(config)#int fast 0/5
SW1(config-if)#spanning-tree portfast
%Warning: portfast should only be enabled on ports connected to a single host. Connecting hubs, concentrators, switches, bridges, etc… to this interface when portfast is enabled, can cause temporary bridging loops. Use with CAUTION
%Portfast has been configured on FastEthernet0/5 but will only
have effect when the interface is in a non-trunking mode.
SW1(config-if)#
Not only will the switch warn you about the proper usage of PortFast, but you must put the port into access mode before PortFast will take effect.
Now, you’d think that would be enough of a warning, right? But there is a chance – just a chance – that someone is going to manage to connect a switch to a port running Portfast. That could lead to two major problems, the first being the formation of a switching loop. Remember, the reason we have listening and learning modes is to help prevent switching loops. The next problem is that there could be a new root bridge elected – and it could be a switch that isn’t even in your network!
BPDU Guard protects against this disastrous possibility. If any BPDU comes in on a port that’s running BPDU Guard, the port will be shut down and placed into error disabled state, shown on the switch as err-disabled. A port placed in err-disabled state must be reopened manually.
BPDU Guard is off on all ports by default, and is enabled as shown here:
SW1(config)#int fast 0/5
SW1(config-if)#spanning-tree bpduguard enable
It’s a good idea to enable BPDU Guard on any port you’re running PortFast on. There’s no cost in overhead, and it does prevent the possibility of a switch sending BPDUs into a port configured with PortFast – not to mention the possibility of a switch not under your control becoming a root switch to your network!
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage, home of free CCNP and CCNA 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 CCNA / CCNP exam questions! Details are on the website.
For a FREE copy of his latest e-books, “How To Pass The CCNA” and “How To Pass The CCNP”, just visit the website! You can also get FREE CCNA and CCNP exam questions every day! Pass the CCNP exam with The Bryant Advantage!
Tags: CCNA, CCNP exam
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