making L2 topology in the CCIE lab !?!


When making this L2 topology in the lab excersises, I´m always having problems and is stucked, with this biulding the very important Layer 2 topology in the lab.

Getting confused, in this part of the configuration !??! I`m using "sh cdp nei" on my switches ? But somehow I cant see the whole L2 topology.


And then connecting router/switch. I know the commands for this, but getting lost every singel time :-(( Is there anything I can read about this somewhere, or some of you could share some excperience her ;-) That would be more than great :-) ...


  • Not sure how you are getting lost. I would say using show cdp neighbors and using the lab itself to fill in some of the gaps. Sho vlan, sho ip int brief, list of what you have and where you have it build a quick diagram based on those. Compare it to your lab booklet to fill in some of the parts. Read the lab a couple of times. Make a list of things you know you are going to need to do in each section. Compare what you got. That's my method. I miss stuff but it is normally because I wasn't paying attention to what they were asking for in the first place.

  • Don't forget the sh int trunk, sh spanning-tree, the SVI in order to have a full L2 topology with the vlan propagation.

  • Or perhaps I should say I am not sure where in a lab you are getting lost. Are you refering to the workbooks? T-Shoot? We would all like to help, and I'm sure most on here are better explaining their process than myself.

  • My fault, I kind of take forgranted my mind thinks things out and I may forget to type them.


    Don't forget the sh int trunk, sh spanning-tree, the SVI in order to have a full L2 topology with the vlan propagation.


  • I am not sure if someone has already wrote down this method in some other post but I thought I will write this down for myself and also share it with my friends. Smile


    The way I remembered (memorized) this is by understanding the physical connectivity. Here's the way our pod is connected:


    All ODD numbered routers are connected to ODD numbered switches. i.e. R1, R3, R5, and BB3 are connected to SW1 and SW3


    All EVEN numbered routers are connected to EVEN numbered switches. i.e. R2, R4, R6, and BB2 are connected to SW2 and SW4


    All the Lower Ethernet segment (i.e. Fa0/0) are connected to lower numbered switch and Higher segment (Fa0/1) is connected to higher numbered switch.

    Ex. R3 Fa0/0 is connected to SW1 fa0/3  and R3 Fa0/1 is connected to SW3 fa0/3.

    3) Backbones are simple - BB2 is connected to SW2 and BB3 is connected to SW3.

    4) Interswitch links:

    The common point in all the switches is that they use ports from range fa0/13 - fa0/21. I broke this range into 3 parts and gave them name - 13-15 range A16-18 range B and 19-21 range C

    For this, Start with SW1

    All the ranges in SW1 (A, B and C) will connect to range "A" in all the switches 

         i.e. SW1 - A is connected to SW2 - A; SW1 - B is connected to SW3 - A; SW1 - C is connected to SW4 - A

    For SW 2, All the "remaining" ranges (B and C) are connected to range "B" of SW3 and SW4.

    For SW3 the only remaining range "C" is connected to SW4 range "C".


    Now, once you understand the pattern of the physical connection, the logical is very easy.

    lets take an example of VLAN 146 between R6, R4 and R1.

    to make this VLAN in appropriate switch, you will see that R1's Fa0/0 is in this VLAN 146 which means that "ODD" numbered router's "Lower" Ethernet is in the VLAN. so by looking at points 1 and 2 above, we can determine that it is connected to SW1. Similarly, R4's Fa0/1 is connected which translates to "EVEN" router and "Higher" interface so it has to be SW4. And in the last, R6's fa0/0 means that "EVEN" router "Lower" interface - so SW2. So in order to get connectivity, all you have to do is create VLAN 146 in SW1, SW2, and SW4


    Hope this makes sense. It might look complicated in first glance, but once you have this pattern in mind, you will be able to do all the workbook volumes with ease not just VOL 1 as in all the volumes, the physical connection is same. 


    Good luck everyone! Smile



  • Hi,

    I initially developed a similar thought process. While it does make things faster, I make a conscious effort not to use it as much as possible because I feel I'm and depriving myself of precious L2 discovery practice. Such a thing could very well end up costing me 1.4k in the near future if I'm not careful :)

    show commands are your friends!

    Just my two cents.


  • I hear you Eric. When I practice on Workbooks; I don't memorize the physical connectivity of INE's topology. I put myself in the real CCIE lab, meaning I do not know what device connect to what switch, and how the switches are interconnected. Because believe me, in the real lab, it's very different, I have been there. I always practice the workbooks using show command even if I know that BB2 is connected to SW2 f0/24 and BB3 SW3 f0/24. It's a waste of time you might say but hey at least in the real lab I would have a "always-use-show-commands" attitude!!!!! 

    Volume 2 Version 5 has, almost in all labs, basic layer 2 and layer 3 are built. That's because at the CCIE level you should be able to do that in a snap of a finger. That's why I think Volume 2 Version 4.1 is still very pertinent because you have to build your layer 2 and layer 3 from scratch. Anyways we have had candidates telling us that their devices had a blank configuration during the lab and they had to build everything themselves.

    So being ready is the key, be very prepared and as fast as possible, but do not confuse speed and rush though.



  • Very true, Eric & Malick,

    Know how to use CDP to quickly verify that the routers and switches are configured to match your lab diagram. If the topology does not match the layer 1/2 diagram, the earlier you catch it, the better.

    As one of our U.S. presidents said: "Trust, but verify." The pod will probably be set up correctly for your lab assignment, but make sure it is so.

    Verify layer 1, verify layer 2, verify layer 3, and then verify routing...

    For my 3 attempts, differing amounts of layer 2/3 was pre-configured. It is still a good idea to verify the pre-configuration through appropriate show commands.

  • I completely agree with you guys. The place where I work I have no other choice but to use show commands and figure out the topology. I "memorized" this pattern while doing workbook 1 labs and initially doing show commands. Once you start doing labs, then this topology fits in your head as it doesn't change.

    But yes, before you memorize, you have to know how to discover your network by using show commands! [:D]

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