Monitoring Fully Switched Networks

So often we have confusion regarding what happens with packets on a switched network.

Below are some good definitions:

What is a switch:

http://www.pcwebopedia.com/TERM/s/switch.html

In a fully switched network, switches replace all the hubs of an Ethernet network with a dedicated segment for every node. Definition of a segment:

http://www.pcwebopedia.com/TERM/s/segment.html

Every port on a fully switched network is by definition segmented. A great link that explains this is on HowStuffWorks.com:

http://computer.howstuffworks.com/lan-switch5.htm

To understand the information that is contained in the packets on the network such as the device IP adresses, MAC adresses or the protocols requires taping into and capturing information as the packets move across the wire. In a fully switched network managed switches give you that capability by creating monitoring ports that capture the packets from a segmented port and duplicate them to the device monitoring and capturing the packet information.

The following link has a great discussion on how to do this on a Cisco switch. This is referred to as a Span port.

Cisco Link

However, the price of Tap's can get expensive. But today low end managed switches are available that can be purchased for the purpose of creating a monitoring port.

Information on Taps can be found at:

http://www.operativesoft.com/html/taps.htm

Basic Network Information

HowStuffWorks.com is an excellent source for getting good basic information about Networks. It does a very good job presenting the information in a logical organized fashion. These link provide information about networking technologies that is necessary for deploying network test, security, management and monitoring software. Some of the links I like for the basics are listed below:

Howstuffworks "How Ethernet Works
How LAN Switches Work
How Internet Infrastructure Works
How OSI Works

How Firewalls Work
How Routers Work
How WiFi Works
How Radio Works

After you get the basics from HowStuffWorks the about.com is another great resource and you can get more detailed network information from a singe link. It is a great resource that should be bookmarked.
about.com basic networking concepts

Blog Purpose

The Purpose of this BLOG is to provide content that will facilitate visitors knowledge about computer networks and how to monitor and manage those networks. I have created it as a resource for my Sales Team, but want to make it available to others.