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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CCNA Cisco Certification Case Study
Posted on June 5th, 2010
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?
line vty 0 4
?privilege level 15
?password baseball
?login
That small Cisco router configuration means three things – first, Telnet access is enabled.? Second, the password is baseball.? Third, the “privilege level 15″ command means that any user who attempts to Telnet to the router and knows the password will automatically be placed into privileged exec mode.? (If that command were not present, the user would be placed into user exec and then prompted for the enable password before being allowed into privileged exec.)
You may not want to give that level of access to all incoming Telnet connections.? If you walked into a client’s router room and saw this configuration on a router, what would it mean to you?
username halas password 0 bears
username ewbank password 0 jets
username ed privilege 15 password 0 mcdaniel
line vty 0 4
?? login local
This configuration means three things as well.? Each user attempting to telnet in will be prompted for both a username and password.? Each individual user must enter the password that’s been assigned to them.? For example, the user “halas”would have to enter the password “bears” to successfully Telnet into this router.? The command “login local” under the VTY lines means that this local database of usernames and passwords will be used for authentication.?
Again, by default, users who are Telnetting in will be placed into user exec mode by default.? Only users with “privilege 15″ in the middle of their username / password definition will be placed into privileged exec immediately upon login.
Notice that zero in each of the username / password statements?? I didn’t enter that when I configured these statements.? This number indicates the level of encryption the password is currently under; a zero is the lowest level of encryption, indicating that the passwords aren’t encrypted at all.?? There’s a single line near the top of a Cisco router configuration that tells you why.. which of these three is it?
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
Simple enough!? The password encryption service is off by default.??? To turn it on. just run the command service password-encryption.? Let’s do so here and then take a look at the configuration.
R1(config)#service password-encryption
username halas password 7 1415170A1E17
username ewbank password 7 070524585D
username ed privilege 15 password 7 082C4F4A08170C121E
Now that’s what I call encryption!?? Note that the zero has changed to a “7″ – that’s the highest level of encryption on a Cisco router, and as you can see, it’s very effective.
Knowing how to read a Cisco router configuration is a valuable skill for both the CCNA certification exam and working with production networks.? Keep practicing, keep studying
, and you’ll have the coveted letters “CCNA” behind your name soon!
Tags: CCNA, Cisco CCNA
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CCNA Cisco Certification Case Study
Posted on June 4th, 2010
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?
line vty 0 4
?privilege level 15
?password baseball
?login
That small Cisco router configuration means three things – first, Telnet access is enabled.? Second, the password is baseball.? Third, the “privilege level 15″ command means that any user who attempts to Telnet to the router and knows the password will automatically be placed into privileged exec mode.? (If that command were not present, the user would be placed into user exec and then prompted for the enable password before being allowed into privileged exec.)
You may not want to give that level of access to all incoming Telnet connections.? If you walked into a client’s router room and saw this configuration on a router, what would it mean to you?
username halas password 0 bears
username ewbank password 0 jets
username ed privilege 15 password 0 mcdaniel
line vty 0 4
?? login local
This configuration means three things as well.? Each user attempting to telnet in will be prompted for both a username and password.? Each individual user must enter the password that’s been assigned to them.? For example, the user “halas”would have to enter the password “bears” to successfully Telnet into this router.? The command “login local” under the VTY lines means that this local database of usernames and passwords will be used for authentication.?
Again, by default, users who are Telnetting in will be placed into user exec mode by default.? Only users with “privilege 15″ in the middle of their username / password definition will be placed into privileged exec immediately upon login.
Notice that zero in each of the username / password statements?? I didn’t enter that when I configured these statements.? This number indicates the level of encryption the password is currently under; a zero is the lowest level of encryption, indicating that the passwords aren’t encrypted at all.?? There’s a single line near the top of a Cisco router configuration that tells you why.. which of these three is it?
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
Simple enough!? The password encryption service is off by default.??? To turn it on. just run the command service password-encryption.? Let’s do so here and then take a look at the configuration.
R1(config)#service password-encryption
username halas password 7 1415170A1E17
username ewbank password 7 070524585D
username ed privilege 15 password 7 082C4F4A08170C121E
Now that’s what I call encryption!?? Note that the zero has changed to a “7″ – that’s the highest level of encryption on a Cisco router, and as you can see, it’s very effective.
Knowing how to read a Cisco router configuration is a valuable skill for both the CCNA certification exam and working with production networks.? Keep practicing, keep studying, and you’ll have the coveted letters “CCNA” behind your name soon!
Tags: CCNA, CCNA exam
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8 Things to Help You Pass CCNA Exa
Posted on May 29th, 2010
I’ve seen many people failed on their CCNA exam while CCNA is the most basic exam of the Cisco certification series.
This is because most of the exam candidates didn’t prepare enough for the exam, got nervous at the exam and failed due to minor mistakes.
I have my own successful way to prepare for the exam, I’ve collected many things to help me pass the CCNA exam.
You may or may not agree to me, yet I got a pretty good score at the exam, only got 1 false answer.
I don’t mean to show off or anything, but my point is anyone can get this score if you prepare properly, so here is my 8 things to help me passCCNA exam:
It is natural to get as many resource about the exam, but too many information can seriously damage your brain. The key is to get the right resource to learn from and focus on them before you decide they’re not enough and search for more.
1. BOOKS
I like the work of Todd Lammle, he explains the materials in CCNA exam with easy ways to understand.
Although books are good but the problem with books is that you can get tired reading them all day long, so I figure I need some other resources.
2. VIDEO TUTORIALS
I highly recommend video tutorials from CBT Nuggets, especially the author Jeremy Ciaora, great video series.
The video is quite expensive US$ 399.00 for the CCNA Certification Package, but I’m telling you its worth the money.
In the video you can watch configuration of true Cisco devices along with the explanation, which Jeremy Ciaora did a great job in explaining the topics.
Video tutorials are great but sometimes they don’t cover everything about the exam – due to the limited time I suppose, that’s why you also need the books to complement each other.
3. BLOGS/SITES
Browse the internetnet, find free exam questions that you can try answering, find out how everyone did the exam, how they succeed, how they failed, this can be a very valuable lessons for you.
Visit my blog often at http://networking-newbie.blogspot.com 
4. CISCO SIMULATORS
You can get many free or paid Cisco Network Simulator from the internet, some are good, some have limited functions:
Dynamips – free router simulator using command line interface (no GUI)
GNS3 – GUI version of Dynamips
Boson NetSim – paid simulator complete with labs samples
Cisco Packet – free simulator from Cisco
It is very important to get your hands on one of these simulators, you need to get yourself a hands on experience configuring cisco devices.
If you have more budget, build your own Cisco home lab.
As one of the readers commented on this post (thank you Robert Williams from certguard.com), I realized that using braindump softwares are illegal, I decided to empty the following two points:
5. QUESTIONS BANK
6. EXAM SIMULATOR
7. TIME
I can’t stress you enough about this, time is very important, you have to invest your time seriously to take the exam. The CCNA exam is not the kind of exam where you can cram yourself to study in the weekend and hope to pass in the following Monday.
When I talk about time, it also means that you have to practice yourself in answering questions as quick as possible, remember you have a very limited time and you can’t go back to previous questions you’ve answered.
So you need to know your self capacity and try to do the exam in a limited time and remember you’d be in a pressure when dealing with the real exam.
8. D-DAY PREPARATIONS
The d-day has come, you’re nervous as hell, plus you can’t bring anything to the exam class except for pens or pencils.
You’d be given a scrap of paper to calculate subnets or something else.
This is a good news, you do allowed to take notes on the paper when taking the exam. Before you get even more nervous, you can write down the keypoints in calculating subnets, for example 8th bit = 128, 7th bit = 64, 5th bit = 32, and so on.
You’d be presented with the exam rules, etc before taking the exam, you have to know well the rules before and take this time to write down your notes.
But remember don’t write down any configuration commands because they might think you’re cheating.
This method of writing notes can help speed your time in calculating subnets.
Why only subnets? I have to remind you that CCNA exam will test you heavily on subnetting, and in my opinion it will be the topic that is taking most of your time in the exam.
Tags: Add new tag, CCNA, CCNA exam, Cisco
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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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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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CCNA Certification: Reloading A Cisco Router Interface
Posted on May 22nd, 2010
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”.
In a previous tutorial, I showed you how to configure an Etherchannel. You have to place each port into the Etherchannel with the channel-group command, and if you do so individually, some of the ports may go into error-disabled state, or “err-disable”. This can also happen as a result of port security enforcement. You can see this with the show interface command:
sw1#show int fast 0/1
FastEthernet0/1 is down, line protocol is down (err-disabled)
A syslog message putting that port into err-disabled state will look like this:
04:10:23: %PM-4-ERR_DISABLE: channel-misconfig error detected on Po1, putting Fa0/1 in err-disable state
If this happens during an Etherchannel configuration, just finish the config and then shut and reopen the ports in err-disabled state. They’ll come back up and be placed into the Etherchannel.
Finally, our old friend the SPID often makes us shut and reopen the BRI interface. If the BRI interface is open and you configure SPIDs on it, the SPID can be absolutely correct and you’ll still see this in the output of show isdn status:
spid1 configured, spid1 NOT sent, spid1 NOT valid
At least the Cisco router puts “NOT” in caps, right? It’s easier to see that way! With SPIDs, before you call the service provider or check the SPID you entered about 40 times, just shut and reopen the interface. That usually does the trick.
When you earn your CCNA certification Feature Articles, that means that you know what you’re doing instead of hoping that you do – and part of that is knowing when a simple reload or open/shut will take care of the issue.
Tags: CCNA, CCNA certification, Cisco
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Passing Cisco’s CCNA and CCNP Exams: Traceroute
Posted on May 20th, 2010
In preparation for your CCNA and CCNP exam success, you’ve got to learn to troubleshoot Cisco routers. And while ping is a great basic IP connectivity tool, it doesn’t give you all the information you need to diagnose network connectivity issues.
Let’s say you have six routers between CityA and CityB. You send a ping from A to B, and get this return:
R1#ping 172.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.1.1.1, timeout is 2 seconds:
…..
Success rate is 0 percent (0/5)
The five periods indicate that there is no IP connectivity to CityB. Problem is, that’s about all ping tells you. You can have 5 or 50 routers between the two points, so how can you tell which downstream router has the problem?
That’s where traceroute comes in. Traceroute sends three datagrams with a Time To Live (TTL) of 1. Those datagrams will timeout once they hit the first router in the path, and that router will respond with an ICMP Time Exceeded message.
In response, the sending router sends three more datagrams, but these have a TTL of 2. This means that the next router in line will send back ICMP Time Exceeded messages. This process continues until the final destination (CItyB) is reached the output of the command shows us the path the data took:
Router1#traceroute 271.1.1.1
Type escape sequence to abort.
Tracing the route to 271.1.1.1
1 20.1.1.1 4 msec 4 msec 4 msec
2 30.1.1.1 20 msec 16 msec 16 msec
3 271.1.1.1 16 msec * 16 msec
How does this help troubleshoot a problem? Let’s say that the second router in this path, 30.1.1.1, doesn’t know how to get to 271.1.1.1. The output would look like this:
Router1#traceroute 271.1.1.1
Type escape sequence to abort.
Tracing the route to 271.1.1.1
1 20.1.1.1 4 msec 4 msec 4 msec
2 30.1.1.1 20 msec 16 msec 16 msec
3 * * *
This indicates that the router at 30.1.1.1 doesn’t know how to get to the final destination. Now you have a better idea of which router has an issue!
Now here’s the bad part: you’re going to get 30 lines of three asterisks, and until you abort this traceroute, you’re going to just watch those asterisks go across the screen. There’s an abort sequence that the router mentions in the first line of the console output, but the router doesn’t tell you what it is! So I will – this top-secret sequence is TWICE, one right after the other.
That keystroke takes a little getting used to, but a CCNA or CCNP can do it! Add this command to your Cisco skill set, and it will serve you well both on the CCNA and CCNP exams and your real-world networks. And you’ll impress your friends by knowing how to stop a traceroute!
Tags: CCNA, CCNP
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