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Learn vital ISDN details you need to know to pass the CCNA exam from Chris Bryant, CCIE #12933.

Cisco CCNA Certification Exam Tutorial: ISDN Details You Must Know

Cisco CCNA Certification Exam Tutorial:  ISDN Details You Must KnowCCNA 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.R2#show interface serial0Serial0 is up, line protocol is up Hardware is HD64570 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec)While theres only one D-channel in BRI, PRI (US) and PRI (EU), the bandwidth of that D-channel does vary from BRI to PRI. Its 16 kbps in BRI and 64 kbps in both PRI versions.The global command isdn switch-type must be configured before you can even begin to have ISDN work. show isdn status will tell you whether or not youve done this correctly.R2#show isdn status **** No Global ISDN Switchtype currently defined ****ISDN BRI0 interface dsl 0, interface ISDN Switchtype = none Layer 1 Status: DEACTIVATED Layer 2 Status: Layer 2 NOT Activated Layer 3 Status: 0 Active Layer 3 Call(s)PAP allows passwords to be different; CHAP requires that they be the same.PAP requires the ppp pap sent-username interface-level command. CHAP has no equivalent command.Define interesting traffic with dialer-list and link that list to the interface with dialer-group.R2#conf tR2(config)#dialer-list 1 proto ip permitR2(config)#int bri0R2(config-if)#dialer-group 1The dialer idle-timeout value is expressed in seconds, not minutes. (Even IOS Help isnt totally clear on this.)R2(config)#int bri0R2(config-if)#dialer-group 1R2(config-if)#dialer idle-timeout ? <1-2147483> Idle timeout before disconnecting a callR2(config-if)#dialer idle-timeout 120Dialer map maps a remote IP address to a remote phone number. You never dial the local routers phone number.dialer load-threshold requires the ppp multilink command to be configured, and the value of dialer load-threshold is expressed as a ratio of 255, NOT 100. For example, if you want the second b-channel to come up when the first reaches 50% of capacity, the value to express with dialer load-threshold would be 50% of 255 which equals 127.R2(config)#int bri0R2(config-if)#encap pppR2(config-if)#ppp multilinkR2(config-if)#dialer load-threshold ? <1-255> Load threshold to place another callSuccess on the CCNA exam depends on knowing the details. Keep studying, keep practicing on real Cisco routers and switches, keep a positive attitude, and you're on your way to CCNA exam success!

Passing The CCNA and CCNP: Home Lab Shopping On Ebay

Passing The CCNA and CCNP:  Home Lab Shopping On Ebay

Whether you're just getting ideas for your Cisco home lab or adding to your existing lab, ebay is a great place to get ideas for your lab as well as pick up some great bargains.Of course, the internet being what it is, there are always going to be a few people looking to take your money while shipping you inferior merchandise, or worse, no merchandise at all. While these "dealers" are in the minority, you still need to be careful when purchasing Cisco equipment on ebay. In this article, I'll give you several tips on browsing ebay ads for home lab ideas, and a few things to look out for when purchasing equipment on ebay.For those of you just starting your Cisco certification pursuit, the idea of purchasing a home lab kit -- a set of routers, switches, and perhaps some cables and study guides -- seems like a good idea. Instead of putting your lab together one piece at a time, these kits allow you to get a head start on your studies.One thing to watch out for in these kits is outdated equipment, or the inclusion of outdated study guides. Often, vendors will use these kits as a way to get rid of unwanted inventory. The Cisco 1900 family of switches falls into this category. A recent search on ebay for "ccna lab" showed seven different CCNA lab kits that contained 1900 switches. The problem here is that the current CCNA exams do not test on the 1900 switches, which are menu-driven and do not have an IOS. You'll need to be well-versed with switches that do have an IOS, such as the 2950s.The plus side here is that you will probably save money by using 1900 switches. If you're on a tight budget, having a 1900 switch is better than no switch at all. If at all possible, though, get a Cisco switch with an IOS.The cables and transceivers included with these kits are generally exactly what you need to set up that particular kit, and this can be very helpful to those CCNA candidates who are new to the various cables needed to physically configure a home lab. Just make sure you're not buying a kit with 10 transceivers (used on AUI ports) when you've only got two routers with Ethernet ports.Watch out for kits that include outdated study guides. I've seen four-year-old CCNA books included with some kits. If you already have your study guides, feel free to ask the vendor how much the kit costs without the books.That leads me to the most important point. Get to know the vendor before buying anything. Visit their website and check their ebay feedback. If buying from an individual as opposed to a reseller, find out what conditions the router or switch has been kept in, and make sure to define the terms under which they will accept returns. There's nothing wrong with buying equipment from someone who's selling their CCNA/CCNP/CCIE home lab, but just make sure you ask the right questions first. Professional resellers generally have their return policy right in their ebay ad; if they don't, ask for a copy.Building your own CCNA and/or CCNP home lab is a little intimidating at first, but speaking as someone who has climbed the Cisco certification ladder from the CCNA to the CCIE, I can tell you that it is the best investment you can make in your career. Use a little caution, ask the right question, and soon you'll be leaving the world of "router simulators" behind - and you'll be developing your skills as a true professional should: On real Cisco routers and switches!

Cisco CCNA Exam Tutorial: Five OSPF Hub-And-Spoke Details You Must Know!

Cisco CCNA Exam Tutorial:  Five OSPF Hub-And-Spoke Details You Must Know!

CCNA exam success depends greatly on knowing the details, and if there's one protocol that has a lot of details, it's OSPF! This is true particularly of hub-and-spoke networks, so in this CCNA OSPF tutorial we'll take a look at some of the more important hub-and-spoke OSPF details. This will help you in working with real-world networks as well, since this OSPF network type is one of the more typical network topologies.In OSPF, the hub must become the designated router (DR). The DR election's deciding value is the OSPF interface priority, and the default value is 1. It's not enough to set the hub's OSPF interface to 2, however, since the spoke routers must not become the DR or BDR. You must set the spoke interfaces to an OSPF priority of zero.R2(config)#int s0R2(config-if)#ip ospf priority 0This ensures that the spokes will not become the DR or BDR if the hub goes down.The hub does require a bit more configuration, though. The neighbor command must be used on the hub to indicate the IP address of the potential neighbors.R1(config)#router ospf 1R1(config-router)#neighbor 172.12.123.2R1(config-router)#neighbor 172.12.123.3It's common to have an ISDN link as a backup in an OSPF network, and when that ISDN link comes up the hello packets must be able to cross the link. What you don't want is to have the hellos keep the link up! By configuring the ISDN link as an OSPF demand circuit, the link will drop in the absence of interesting traffic, but the OSPF adjacency that formed across the ISDN link will be assumed by the router to still be up. (You usually see this command configured on both sides of the ISDN link, but it's only needed on one side. It doesn't hurt anything to put it on both sides, though.)R2(config)#int bri0R2(config-if)#ip ospf demand-circuitA final detail of OSPF hub-and-spoke and demand circuits actually takes place at Layer 2. For the OSPF hello packets to successfully be transmitted across an ISDN link or a frame relay network, the broadcast option must be enabled in the appropriate frame and dialer map statements. Failure to enable this option can lead to a situation where pings will be successful, but OSPF adjacencies will not form. R2(config-if)#dialer map ip 172.12.21.1 name R1 broadcast 5551111R2(config-if)#frame map ip 172.12.123.1 221 broadcastWhen you're troubleshooting OSPF in a production network or your CCNA / CCNP home lab, don't just look at Layer 3 - because everything's got to be right at the physical and data link layers in order for the network layer to function correctly!

Cisco CCNA / CCNP Certification Tutorial: Frame Relay End-To-End Keepalives

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.What you have to keep in mind about FREEK is that each and every PVC needs two separate keepalive processes. Remember, with a PVC, there's no guarantee that the path taking through the frame relay cloud to get from R1 to R2 is going to be the same path taken to go back from R2 to R1. One process will be used to send requests for information and handle the responses to these requests; this is the send side. When the send side transmits a keepalive request, a response is expected in a certain number of seconds. If one is not received, an error event is noted. If enough error events are recorded, the VC's keepalive status is marked as down.The process that responds to the other side's requests is the receive side.This being Cisco, we've got to have some modes, right? FREEK has four operational modes. Bidirectional mode enables both the send and receive process enabled on the router, meaning that the router will send requests and process responses (send side) and will also respond to remote requests for information (receive side). Request mode enables only the send process. The router will send requests and process responses to those requests, but will not answer requests from other routers. Reply mode enables only the receive process. The router will respond to requests from other routers but will initiate no requests of its own. Finally, passive reply mode allows the router to respond to requests, but no timers are set and no events are tracked. Frame Relay End-To-End Keepalive defaults:Two send or receive errors must be registered in order for the VC to be considered down.The event window size is three. The event window is the number of events considered by the router when determining the status of the VC. Therefore, using the defaults, two send or receive errors would have to be received within the event window of three events for the VC to be considered down.The timer mentioned earlier - the amount of time a router waits for a response - is set to 10 secondsWorking with Frame Relay end-to-end keepalives is just one Frame skill youll need to pass the CCNP exams and I wouldnt be surprised to see them on a CCIE exam. Know the details and youre on your way to Cisco certification exam success!

Computer Consulting 101 Hiring Tips (Part 1 of 2)

Does your business need the services of a computer consulting firm? Before you rush out and hire the first techie or slick-salesperson that knocks on your door, be sure to consider these favorite Computer Consulting 101 hiring tips for screening and interviewing local computer consulting firms. In this first in a two-part series, well look the root of the problem, as well as the four most basic criteria that youll need to ask about when searching for computer consulting vendors.Computer Consulting 101 Preventative MedicineMany small business owners have a tough time knowing how to deal with difficult computer consultants. However, if you're able to uncover potential problems at the start of your computer consultant/client relationship, you can avoid many of these unpleasant issues altogether. Root of the ProblemWhile most entrepreneurs and small business managers know exactly what to ask when it comes to hiring for internal staff positions, hiring a computer consulting firm can be more difficult.So on top of dealing with the myriad legal issues surrounding how you retain the services of contractors (best advice: consult with your attorney), as opposed to hiring employees on your payroll, you'll need to know how to ask the "right" questions. Don't make the ultra-common common mistake of focusing on the wrong things. Use these Computer Consulting 101 Hiring Tips as your checklist for doing your homework before you sign on the dotted line.Part-time or Full-time Computer ConsultingDo you have a "day job"? Are you moonlighting?Solo Practitioner or True Computer Consulting BusinessWhat do you mean by the "we"? Are there any other people who work at your company?Are they employees or contractors? What are their names, specialties and backgrounds? How long have they been with the company? Will they be involved with this account?(Tip: The more pointed questions you ask, the more youll flush out the B.S. and hyperbole.)Small Business or Large Company Computer Consulting ExperienceWhat "size" is your typical consulting client, in terms of number of PCs, employees and annual revenue?Generalist or Specialist Consulting CompanyWhat industries or vertical markets have you worked with? And in what particular aspects and software applications? What kinds of products, services, and platforms does your company shy away from? Do you work with any specialty hardware, software or services vendors?The Bottom LineIn this first of a two-part series of these Computer Consulting 101 hiring tips, we looked at why small business owners and managers find that computer consulting companies are so difficult to hire, as well as four basic issues that you must confront when searching for a new computer consulting vendor. In the second installment of this two part series on Computer Consulting 101 hiring tips, well look at how you can get your hands around the true costs of using a computer consulting firm, as well as how you can more objectively evaluate the computer consulting firms suitability for the task of servicing your companys technology needs.Copyright MMI-MMVI, Computer Consulting 101. All Worldwide Rights Reserved. {Attention Publishers: Live hyperlink in author resource box required for copyright compliance}

Cisco CCNP / BCMSN Exam Tutorial: Configuring PortFast And BPDU Guard

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 0/5SW1(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 0/5SW1(config-if)#spanning-tree bpduguard enableIt'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!

Summary

Learn vital ISDN details you need to know to pass the CCNA exam from Chris Bryant, CCIE #12933.