Any good free beginner network simulators out there for troubleshooting practice?

I hear simulators are common with cisco certification, but that's a bit above my level, I'm currently studying Network+.

Wondering if there are any good simulators to help get more hands on experience actually doing troubleshooting?
Example, the sim could have a DNS server that goes down, and you have to properly diagnose it with the command line tools.
Or somehow a routing table gets screwed up, and you have to identify the problem.
Or in general, something is acting up somewhere, and you have to solve it.

Do any good free simulators exist?

I suppose with a strong pc you could take the time setting up a virtual network of a bunch of virtual machine software servers, and intentionally break and fix them, but that's a lot of work, and if your doing the "breaking" you wouldn't be challenged to know what to fix. Would be cool if there was software with increasing complexity like a game, so you start with small business networks, then move up to bigger more challenging networks.

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Comments

Asif Dasl

This is just me, but I find it's better to know what you're breaking and fixing instead of not know what you are doing and breaking stuff to fix it. There is a learning process in both but I find reading a book before you break/fix it in the lab more beneficial.

But yes, running VMs or GNS3 or PacketTracer is how you learn. Lab, lab & lab some more. Real world is where you get the scenarios where your labbing comes in to it's own. And the more real-world experience you've got the better your troubleshooting becomes.

Just my 2 cents.

DevilWAH

if you can get cisco Packet tracer then start with that. The big benefit it has over GNS3 is the simulation mode. Here you can watch a packet transverse the network hop by hop in a nice clickable GUI.

http://1.bp.blogspot.com/--aU4zdHmlts/T7tQAoASZXI/AAAAAAAABPU/p75eKV8c0j8/s640/1.png

so you can click to step forward and watch the packets transverse the network and click on them to see what is happening, if you have an error it will tell you why the packet gets dropped or is not forwarded.

Packet trace will take you through the CCNA certifications, but after that GNS3 is the best next step, or real equipment if you can afford it (mixture of both is best). Packet trace is a simulator so is very limited in the advanced functions that GNS3 as a emulator of the Real equipment does not suffer from, but if you dont have a basic understanding of GNS3 it can be a sharp learning curve and again unlike packet tracer does not come with example networks you can load up and practice / learn on.