#CCNA and #CCENT Lab Topologies

certskills
By certskills August 21, 2013 09:05

To build a lab for #CCNA or #CCENT practice, you need to think about how many routers you need, how many switches, and how many interfaces of each type. To make those choices, you need to think about the topologies you can build, and what features need the larger topologies. Eventually, this kind of analysis lets you compare the cost to buy enough gear for each topology vs. the features that can be best practiced with progressively larger topologies.

Today’s post takes us through a discussion of some topologies for CCNA and CCENT, covering the basics for those of you early in your CCENT or CCNA studies.

Related posts:

 

The Big Concepts: Topologies, Interfaces, Functions

To begin, do not think about making an individual purchase. Do not start with the idea of thinking about buying a router, switch, or a cable. Instead, begin as follows:

  1. Think about some of the topics you want to study, like those in your CCENT or CCNA books.
  2. Think about the topology of routers, switches, PCs, and cables needed for an effective lab exercise with that feature. (If you are just starting out, you may not know enough to figure this part out on your own.)
  3. For a given topology, count the number of routers and switches needed
  4. For each device in a topology, count the number of each type of interface needed on each device in each topology

If you can get through these first four steps, you are closer to being ready to pricing our your options for buying used gear, plus you know the value you receive: the types of features you can practice depending on how much gear you buy.

To define terms, the word topology in this case refers to the conceptual drawings of networks like those you see in your cert study books. The figures include routers, switches, user devices like PCs, and cables that connect those devices.

Those drawings also imply something about the interfaces on the various devices. For instance, Figure 1 shows two routers, one switch, one PC, with cables. Implied by the interface identifiers is the fact that each router has:

  • (at least) one serial interface
  • (at least) one Ethernet interface of some type

Figure 1: Sample Two Router, One Switch Topology

As another example, consider figure 2. From a quick analysis of the figure, you can see that the following devices and interfaces would be needed:

  • Three routers, each with:
    • Two serial interfaces
    • One Ethernet interface of some type
  • Three LAN switches
    • Four Ethernet interfaces of some type

Figure 2: Sample Three Router Topology

Topologies Allow Lab Exeriments with Different Features

If you are reading this blog post before you have done a lot of your CCENT or CCNA study – which is a good time to start thinking about lab gear, by the way – you have a disadvantage in that you don’t yet know much about the you’ll be experimenting with using all this lab gear. If that’s you, and you look at figures 1 and 2 in this blog, it’s hard to know whether the first topology (with less gear) is enough gear to work with, or if you need the additional gear shown in the second topology. Do you need more? Less? And what benefits do you get with more or less gear, with more or less interfaces, to create different topologies?

As it turns out, even a single router, along with your existing PC, can help you learn some of what you need for CCENT and CCNA. Yes, a single router, even a single old (and cheap) router. Let me give you an example.

Say you buy one used Cisco router, with an old IOS (call it version 12.2), which would have been commonly used in production networks over 10 years ago. You already have a PC with an Ethernet port, and a serial port (USB or traditional). You buy a console cable to connect the PC to the router console, and buy crossover Ethernet cable to connect the laptop to the router’s Ethernet port (no LAN switch needed). You end up with the lab as shown in Figure 3:

Figure 3: Single Router Lab

It seems almost too sparse, but you can still learn with this single router. For instance, you can:

  • Learn basic CLI navigation through CLI modes
  • Learn the configuration process
  • Configure and test Telnet passwords
  • Configure and test SSH passwords
  • Set and test the enable passwords
  • Configure and test hostnames
  • Experiment with the ping command (simply)
  • Configure and test router Ethernet settings (speed, duplex)
  • Configure everything (but without the ability to test to see if many of those features work or not)
  • Configure and test some other administrative settings

As you see, you can learn something even with a single router. In fact, if you have never seen a Cisco router or switch, I think it’s worth buying at least one router, just to learn how to connect to the console, and experience that directly.

Some Features Require More Nodes (Routers and Switches)

While the single-router topology of Figure 3 is useful, the simple fact is that for some features, you need more routers and more switches to do a meaningful lab for a given feature.

For instance, Open Shortest Path First (OSPF) is the one IP routing protocol discussed for the current CCENT certification. With one router, you can configure OSPF, but you cannot learn much about whether it works. OSPF works by communicating between routers, so you need at least two routers, like with the topology in Figure 1. However, OSPF also has features that make choices about alternate routes, and have at least three routers, with alternate routes, as shown in Figure 3, allow you to learn even more.

Summing up what you can do with one, two, and three router topologies with OSPF lab experiments:

  • One router: Configuration only, with almost no useful learning about OSPF verification
  • Two routers: Configuration, plus basic verification, and basic redundancy (with multiple links between the two routers)
  • Three routers: Adds more interesting options for redundant routes and how OSPF uses them, plus more design options with OSPF areas

Finding the Main Topology Comparisons at Certskills.com

As I mentioned in the introductory post in this series, some topics about building a lab work better as a blog post, but others work well as reference material on a web page. Comparisons of topologies, and how they can be used to learn for CCNA, are best kept on a permanent web page. So, I’ve collected these kinds of notes at this web page for the CCNA exam:

http://certskills.com/LabGear/CCNA/Topologies.aspx

This page (and a similar one for the CCNP cert) shows several topologies of different sizes, some with routers, and some with switches. It also lists the kinds of features you can best learn with each topology – by adding more and more to make larger topologies, you can more features using features that make sense. So, rather than re-list this reference information here, take a look at the web page, and think about those options.

So, What Do You Plan to Do?

So, for those of you just getting into building your lab, what’s your current plan? After reading today’s post, are you thinking of starting out with enough gear for a two-router topology? Or even a single router? I’d be interested to hear.

 

#CCNA and #CCENT Lab Gear
IOS Version 15 for a Cisco Home Lab – or Not
certskills
By certskills August 21, 2013 09:05
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16 Comments

  1. Momodou September 1, 06:57

    I have 3 routers(2 x 2621XM, 1 x 2611XM) as well as 3 switches(2 x 2950, 1 x 3550). All 3 routers have a WIC-2T installed. Planning on using the topology on figure 2. Then I’ll break it down and try a different topology.

    Reply to this comment
    • CCENTSkills September 4, 10:04

      Yep, Figure 2 – the 3-router triangle as I like to call it – is the most classic CCNA topology. You get a little bit of routing protocol redundancy, a couple of routing protocol neighbors, which is good. Enjoy!

      Reply to this comment
  2. Ben September 2, 08:45

    I’m still deciding, but after reading a few of your posts, I really think that a multiple router/switch setup will be the way to go, 3 of each. And after just finishing your comparison on IOS versions, I want to at least get 12.4T.

    Now off to find some good used hardware!

    Reply to this comment
  3. CCENTSkills September 4, 10:05

    Ben- ah yes, the fun part – searching for bargains. I’ve recently seen some TV shows where you trade up from one thing to the next – maybe you can start with a toaster, and trade up to a router! 😉 Hope the shopping goes well.

    Reply to this comment
  4. Joe September 16, 23:02

    I was fortunate enough to receive a great lab setup from the beginning. I have 3 routers (2821) along with 3 wic-2t cards and 1 nm-4a/s. 4 switches(2×2950 and 2×3550) My plan is to work through all the topologies except for the routing squares. I will do those on my way to CCNP! 🙂

    Reply to this comment
  5. CCENTSkills September 20, 19:05

    Joe, that’s plenty good for CCNA. Sounds like a great setup! enjoy your labbing.
    W

    Reply to this comment
  6. mohamoud November 6, 02:24

    i have 2 routers 2620,2650 series and 2 3548 XL switches is that enough for practice for CCNA

    Reply to this comment
  7. CCENTSkills November 6, 08:05

    Mahamoud,
    It’s enough devices. Whether it’s good enough software to practice all the features requires a much longer answer – just check the last 8 blog posts.

    Reply to this comment
  8. Raymond November 17, 20:45

    So here is what I have pieced together over the last few months while also studying.

    3 – 1720s(2x WIC-1T modules each)
    1 – 2600 (2x WIC-1T modules)
    1 – 3550(48port w/ 1gbic)
    1 – 2950(24 port)
    1 – 2960(8 port with 1g SFP)
    1 – 5505 ASA
    1 – 1200 WAP

    Here is my issue, I really want to use all of this as a full home network & lab so I can have some real world experience but I can’t decide how I really want or need to connect it all. It currently functions as my home network and internet connection via ICS on a WIN XP machine using Verizon Wireless USB adapter because of where we live we do not have real broadband. This function works great after many hours of pull my hair out to get it all to work right. Although I learned a ton from it. I would really like to use the ASA as the connection between my ICS XP machine and the rest of the network while also splitting up the servers (2-WIN2008R2 DNS & DFS) from the rest as they could act as they are remotely located. Also I would like the wireless to be separate “remote” location. And suggested topology you would recommend? I know I am a gear junky 🙂

    Reply to this comment
    • CCENTSkills November 18, 11:00

      Sure, a few ideas.
      Get 1 WIC-2T, and pick one router as a central site router, now w/ a total of 3 serial interfaces. The other three routers now become 3 remote sites in concept.
      At the main site, pick a switch, connect the router, the ASA, then the XP machine, as you suggested.
      At two remote sites, use the other two LAN switches as the branch switches.
      At the remaining remove site, connect the router to the WAP w/ a crossover, and just use wireless for that remote site.
      That gives you a nice 4-site WAN. You can pick where to put your two servers.

      For LAN-centric testing, you’ll want to connect the LAN switches, disable some/all the links to the routers, and then you can do some STP testing, for instance.

      Hope this helps! Sounds like a nice setup.
      Wendell

      Reply to this comment
  9. Arsen February 9, 17:25

    I got a lab and all my Serial WAN cards are WIC 1DSU-t1 should I buy WIC-2T for the labs?

    Reply to this comment
  10. JDBoelter May 5, 14:05

    One question – How well would a 3 router lab setup work in a normal US house? I have no idea what the power requirements would be. Can I run a setup like this off a powerstrip/UPS device without tripping a circuit breaker?

    I would be willing to rent some office space in a business park somewhere for a few months to run this setup, but if my house can handle it, a home setup would be much more desirable.

    Reply to this comment
    • CCENTSkills May 5, 16:02

      Hi JD,
      I’m sure you can get the power specs for every Cisco product at cisco.com if you want to do the math. That said, I’ve run 8-12 enterprise class routers and switches at the same time, on one circuit at my house, and never tripped a breaker. I would imagine if you had some switches that (a) supported power over ethernet and (b) you were using them to power devices, or if you had a larger switch, that you might overload a single circuit. But for the sake of a lab, you could always run an extension cord from another room that’s on a different circuit and get more power. But I think for the 3-router/3-switch lab topology, for what most people would afford for home use, you have no worries.

      Reply to this comment
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