*TechNotes* CCNA

WebmasterWebmaster Admin Posts: 10,292 Admin
Following is a list of TechNotes for the CCNA exams. Let me know if you have any comments, suggestions.

icon_arrow.gifBasic Router Configuration and Management

icon_arrow.gifLAN Technologies

icon_arrow.gifOSI model

icon_arrow.gifIPv4 Subnetting Guide *New*

icon_arrow.gifIP Access Lists

icon_arrow.gifCisco Discovery Protocol (CDP)

icon_arrow.gifIntegrated Services Digital Network (ISDN) (no longer that relevant but left here per request)



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    WebmasterWebmaster Admin Posts: 10,292 Admin
    Oh well, the configuration basics turned out to be a little bit more :)

    Still need to add a piece about "configuring banners", which is also getting bigger than I expected icon_wink.gif but will be added soon.

    I hope you like it!

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    WebmasterWebmaster Admin Posts: 10,292 Admin
    And here's another one: LAN Technologies

    Covers Ethernet and eventual problems, LAN segmentation and components and full- and half-duplex.

    Some parts will probably be moved to and/or explained in more detail in another TechNote (Switching/Bridging)...

    Johan icon_rolleyes.gif
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    Added a new CCNA specific OSI model TechNote covering the OSI Reference Model & Layered Communication exam objectives.

    ISDN is probably next...
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    For our members the CCNA TechNotes are now also available in a printer-friendly version without advertisments or anything else, just the text and images. There's an icon and a link to it at the top in every TechNote.

    Johan :D
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    :D Finally finished the ISDN TechNote ... a lot of sweat in this one ;) and thanks to sikdogg for some input!

    Anyone with comments on this one be sure to let me hear them.

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    overkastoverkast Member Posts: 3 ■□□□□□□□□□
    Hey Johan,

    Just letting you know that all your hard work has not gone unnoticed. I'll be reading your summaries!

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    WebmasterWebmaster Admin Posts: 10,292 Admin
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    :D Just finished a new TechNote for the CCNA exam:

    IP Access Lists

    Let me know if it isn't thorough enough :)
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    hiboy_xuhiboy_xu Member Posts: 1 ■□□□□□□□□□
    i like this forum
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    mishoomishoo Member Posts: 43 ■■□□□□□□□□
    hiye webmaster!!

    these notes are really excellent icon_thumright.gif u r gr8 man icon_king.gif
    i m going through them to be preparaed for CCNA icon_wink.gif
    are they enough for thr preparation icon_confused.gif:

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    hnauhnau Member Posts: 2 ■□□□□□□□□□
    Really good notes.. Frame-Relay can also be of interest for 607
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    Thanks guys,
    are they enough for thr preparation
    No, first I'm not finished writing all the TechNotes for the CCNA exam yet. Second, you should never rely on a single source. You should combine other material with our TechNotes, a CCNA CBT or book for example.
    Frame-Relay can also be of interest for 607
    Yes, and we will have it in the future, it is still under construction. icon_wink.gif
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    mishoomishoo Member Posts: 43 ■■□□□□□□□□
    hiye webmaster

    i will be waiting for further notes for the CCNA exam....n plus now i will never rely on single source icon_cool.gif ..........

    thanks for ur kind advice..

    take care
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    AnimeFrusionSmoothieAnimeFrusionSmoothie Member Posts: 22 ■■■□□□□□□□
    I have a question about the basic router configuration:

    Router(config)#line aux 1
    Router(config-line)#password cisco123

    Isn't it supposed to be "line aux 0"?

    (of course i would be done with the test when i see this answer -- but still...)
    PC Modding at it best -
    Xoxide.com, Directron.com, frozenpc.com, frozencpu.com
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    djjitdjjit Member Posts: 40 ■■□□□□□□□□
    Johan, you’re are a legend!! The OSI Model is excellent.

    I learnt something I didn’t know icon_confused.gif: icon_exclaim.gif i.e. NETBEUI icon_arrow.gif belonged to the Transport layer.

    Thanks once again

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    WebmasterWebmaster Admin Posts: 10,292 Admin
    I guess compliments like that make it all worthwhile :D
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    I was planning on finishing the Routing Protocols TechNote next week, but I'll probably won't have time to do so, since I'm working full-time on finishing the Network+ PDFs. So I decided to just post some of the parts I've completed, so maybe I can get some comments and/or suggestions before I post the complete TechNote.

    Routing Protocols


    The process of routing consist of two main tasks:
    - determining the optimal path (route) to a destination.
    - transferring data packets across internetworks.
    Routing occurs on the Network layer (layer 3) of the OSI model.

    Routed vs Routing Protocols

    Routed protocols such as IP, IPX, and AppleTalk are protocols that allow data to be transfered in networks. Routers are used to route the packets between networks. You can configure these routers to use static routes for all your networks, but when the network contains many routers with several LAN and WAN connections, it can become a tedious job to configure all the routes. And when a router fails you will have to manually configure a new route. The solution to this is the use of routing protocols, these allow routers to exchange information about the network and its route, this is called dynamic routing.

    Routing Tables

    Routing protocols maintain a table with entries for routes to different networks called the Routing Table. An example of an entry in the routing table is:
    D [200/128] via, 0:02:22, Ethernet2

    "D" means the routed is dirived by EIGRP.
    "" indicates the address of the remote network.
    "[200/128]" indicates that the administrative distance is 200 and the metric is 128.
    "via" specifies the address of the next router to the remote network.
    "0:02:22" specifies the time the route was last updated.
    "Ethernet2" specifies the interface through which the network can be reached.


    Routing protocols support one or more metrics, which are used in routing algorithms to calculate the optimal route to a destination.

    Convergence Time

    Convergence time refers to the time it takes for all the routers in a network to update their routing tables whenever a network change occurs, i.e., when a link goes down or is added to the network.

    Administrative Distance

    The administrative distance is used to determine which route should be taken to a destination, if a router has multiple routes from different origin. The route with the lower administrative distance will be preferred. For example, when a router learned a route from the OSPF routing protocol and has a static route for the same destination, the static route will be used. Also, when a router is configured with multiple routing protocols, the route of the protocol with the lowest administrative distance will be used. An administrative distance of 255 means the routing information source cannot be trusted, and should be ignored. The default administrative distances for static routes and those originated from routing protocols are listed in the table below:

    Directly connected interface 0
    Static route using IP address 1
    EIGRP summary routes 5
    Internal EIGRP 90
    External EIGRP 170
    IGRP 100
    OSPF 110
    IS-IS 115
    RIP 120
    External BGP 20
    Internal BGP 200
    Route of unknown origin 255

    Distance Vector vs Link-State Routing Protocols

    Routing protocols can be divided in two main types; distance vector and link-state protocols.
    A distance vector protocol is typically used in small to medium sized networks. A router using a distance vector protocol will broadcast its entire routing table periodically out of all its interfaces.

    Link-state protocols are typically used in larger internetworks, they provide faster convergence, consume less bandwidth, and are more scalable. A router configured to use the link-state protocol sends partial updates to only its neighboring routers using multicast. It establishes a formal relationship with neighbors through the use of periodic hello packets. When router stops receiving hello packets from a neighbor for a configurable amount of time, it will consider the router as unreachable. Using link-state protocols in large networks results in lower bandwidth and CPU usage than using distance vector protocols. Link-state routers maintain a topology table apart from a routing table. The routing updates exchanged between link-state routers contain information about the router's links, the current state of the link. Using the shortest path first algorithm, the best route is calculated based on the information in the topology table and stored in the routing table.

    A third type of routing protocols is known as hybrid. The best example of a hybrid routing protocol is EIGRP. It is a distance vector protocol with link-state characteristics, routing updates can be partial, and they do not need to contain the complete routing table such as with RIP and IGRP. Also, updates are not send periodically, but only when necessary, and only to those neighboring routers that need to know.


    A static route is a manually configured route. Static routes are typically used in very small networks and at the boundary of an Autonomous System, for example at the router that connects a LAN to the Internet. The default administrative distances for static routes is 1, hence typically it will be preferred over a dynamic route learned from a routing protocol. The advantage of using static routes is that it is less CPU intensive than using routing protocols, no bandwidth is wasted by routing updates, and it offers full control over the paths a packet should take. Static routes can be propegated throughout a network using routing protocols.

    The following network diagram shows a simple network in which static routing should be used.


    In order for Host A to be able to communicate with Host B, RouterA must have a route to network Use the following command to create a static route on RouterA:
    Create a static route on RouterB using the following command:

    A default route is the route every packet is send to, when there is no other route available for the destination. This is similar to configuring a client with a default gateway.
    Use the following command to create a static default route:
    Router(config)#ip default-network


    Johan :)
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    diplodiplo Member Posts: 1 ■□□□□□□□□□
    Thank, it is very kind to see your course.
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    I just added another TechNote for the CCNA INTRO 640-821 and CCNA 640-801 exam:

    icon_arrow.gifCisco Discovery Protocol (CDP)
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    Phil3021Phil3021 Member Posts: 17 ■□□□□□□□□□
    Johan, I just would like to show my appreciation for the tech notes. Job well done. I bet that would of kept you busy for a while.
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    Thanks Phil!

    I'm currently rewriting/editing some parts of the previous CCNA TechNotes to divide it per CCNA exam (intro, icnd, and 640-801). Also, a lot of information from the 70 pages Network+ TechNotes apply to the CCNA intro exam (hence also the 640-801 exam), so I'm porting some of that info to CCNA TechNotes. I should have some new/updated TechNotes online next week. As well as some new practice questions. :D
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    matcheymatchey Member Posts: 33 ■■□□□□□□□□
    webmaster, these notes are excellent, had been surfing the web wasting valuable time looking at all differnt sites picking bits and pieces of notes from each for ccna, i think i have found one site that covers everything.

    your time and effort are greatly appreciated.

    u mentioned u are going to divide the notes up into intro, icnd, this is the route i am going down, this would be very helpful

    many thanks
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    2lazybutsmart2lazybutsmart Member Posts: 1,119
    wow Johan; you must've put a lot of time into these TechNotes. They're clear and to-the-point. The drawings are deadly.

    Just 1 thing: In the LAN Technologies TechNote, I clicked the link for the complete objectives and I think it's still linked to the 640-607 page. Thought you might want to know that.

    Thnx :P
    Exquisite as a lily, illustrious as a full moon,
    Magnanimous as the ocean, persistent as time.
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    mwgoodmwgood Member Posts: 293
    Excellent technotes.

    I found this in the cdp module:

    "...CDP devices send out periodic advertisements to the MAC multicast address 0100.0ccc.cccc, every 30 seconds by default."

    Are you referring to the CDP timer? If so, shouldn't it be every 60 seconds?

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    WebmasterWebmaster Admin Posts: 10,292 Admin
    You are absolutely right. icon_redface.gif

    The way to remember the holdtime is it is 3 times the update timer... I should have noticed something was wrong.

    I usually tripple-check all facts I write down, obviously didn't this time... my CCNA guide from Osborne says it is 30 seconds but I have 3 Cisco books and one Sybex book that say it's 60 second. I should have checked the Cisco site like I usually do. I'm sorry if I confused anyone.

    Thanks for spotting the error, I'll correct it immediately.
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    danilzhangdanilzhang Member Posts: 4 ■□□□□□□□□□
    hi webmaster,

    iam new here. Recently, i downloaded some exam papers and that version is 640-607...whats the difference btw 640-801 and 640-607??
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    walaboomwalaboom Member Posts: 23 ■□□□□□□□□□
    TechNote saying NIC is physical layer device, it is actually datalink layer device......
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    GordenGorden Member Posts: 1 ■□□□□□□□□□
    walaboom wrote:
    TechNote saying NIC is physical layer device, it is actually datalink layer device......

    NIC should be in Physical Layer,
    Switch is in Data Link Layer and Router is in Network Layer

    Correct me if i m wrong
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    WebmasterWebmaster Admin Posts: 10,292 Admin
    That is correct Gorden. Check out the following discussion (and there are more older posts about this in the net+ forums):

    and this one:
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    elveyelvey Member Posts: 1 ■□□□□□□□□□
    You can prevent SMTP traffic originating from the WANs from traveling over link A by putting an outbound extended IP access list on the Serial 0 interface of RouterX. Use the following commands on RouterX:

    router(config)#access-list 105 deny TCP any host eq SMTP
    router(config)#access-list 105 permit IP any any
    router(config)#interface serial 0
    router(config-if)#ip access-group 105 out
    Doesn't that only prevent SMTP traffic originating from the WANs from traveling over link A IF its final destination is, but allow other SMTP traffic from the WANs over link A?

    - oh, and thanks!
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