Slashdot Mirror

What about OPNET? I thought it would've been obvious, but I haven't seen it mentioned below. It may not be cheap, but it's a professional-quality tool, and it lets you easily design and simulate protocols by drawing state machines. I used this while working on 802.11n proposals back in the day, and I'd still recommend it.

Actually OPNET is available on Linux as well. Its officially supported on redhat, but you can get it running on other distros. The OPNET version for teaching use is called IT Guru Academic Edition.
http://www.opnet.com/solutions/system_requirements/itguru_networkplanner/
http://www.opnet.com/university_program/itguru_academic_edition/

Actually OPNET is available on Linux as well. Its officially supported on redhat, but you can get it running on other distros. The OPNET version for teaching use is called IT Guru Academic Edition.
http://www.opnet.com/solutions/system_requirements/itguru_networkplanner/
http://www.opnet.com/university_program/itguru_academic_edition/

Here are a few tools:

GNS3 - http://www.gns3.net/ - free network simulator, based on Dynamips Cisco emulator
Opnet - http://www.opnet.com/ - detailed planning of networks, from scratch
Traffic Explorer - http://packetdesign.com/ - plan changes to an existing network

You shouldn't be surprised how many cycle hungry programs require Windows (or in some cases, require Windows if you want to make use of all of your hardware). We bought the above mentioned monster machine for Opnet, which will gladly eat every single cycle on any machine when you start running larger simulations.

For freeware, you can't beat ethereal. I use it several times a week.

If you have a serious budget, check out OpNet, which can do fun things like response time breakdowns, or "how well will this app run if the client is across the country instead of next to the server," or "what happens if I have another 300 clients like this one submitting requests @ 5/minute with a poisson distribution", or "If I make the following configuration change to router X, then router Y fails, and we have a network backup running, how much interruption in the transaction will occur."

Opnet

I've been looking at this recently to see how different things will affect my network, since I can't really test them on the live network without making a lot of people and clients really mad. I have not used it yet though.

I prefer to design the network simply using Visio to get a good logical design, and then once that is down, I create another map with the physical layout. Worry about your routing protocols after you have figured out the best logical design (redundancy, required link speeds, etc.). Most network admins have a favorite routing protocol, which for most seems to be EIGRP with cisco equipment. I personally like OSPF because it offers enormous flexibility, and it works with equipment from vendors other than Cisco.

There's a fine line between an ingeniously designed network and something that is overly complex. It takes experience to figure out where that line is. If it seems like you are doing something screwed up, you probably are.