Spanning Tree Protocol

What is spanning tree?

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Spanning tree protocol, also known by the acronym STP, is a Local Area Network protocol which is used to prevent bridging loops in local segments of the network.   This is done through an election process of a root bridge on the LAN segment. The root bridge is the logical center of the segment and can see all traffic that is traversing its network. 

What is a Bridge Protocol Data Unit?

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Configuration BPDU is used by Spanning tree protocol to provide and exchange information between all switches on the local segment.  The information in the frame will consist of the physical MAC address of the source port (originating switch port) and the multicast address destination of 01:80:C2:00:00:00.  The BPDU allow the switches to elect a root bridge for the segment and designate port states that will create a single functioning path back to the root bridge.

The information contained in the Bridge Protocol Data Unit consists of the BPDU Type, Root ID and the Root Path Cost.  The type communications if the BPDU is a configuration BPDU or a topology change BPDU.  The Root ID communicates to the other switches what the priority is for the source switch and what the physical address (MAC Address) are for the root bridge on the segment.  The root cost field is used to calculate the lowest cost back to the root bridge.

Port election states

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Physical links between the switches are then designated either a forwarding port or a blocking port.  The goal of STP is to create a single patch back to the root bridge, therefore eliminating multiple paths to the root bridge.

Blocking – A blocked port is a port that would cause a bridging loop if it was in a forwarding state.  No user data is sent or received over a blocking port, but it may go into forwarding mode if the other links in use fail and the spanning tree algorithm determines the port may transition to the forwarding state. BPDU data is still received in blocking state.

Listening - The port is processing BPDUs and awaiting possible new information that would cause it to return to the blocking state. It does not populate the MAC address table and it does not forward frames.

Learning – A port which is not yet forward frames.  It does learn source addresses from frames received and adds them to the filtering database (switching database). It populates the MAC Address table, but does not forward frames.

Forwarding - A forwarding port receives and sends data under normal operation.

Disabled – A disabled port can be manually disabled by the network administrator.

Nine Reasons Why You Would Benefit From Using Gmail

Gmail is a powerful email agent that can be enjoyed by many and all.  I personally use it to help me stay organized with all of my personal correspondence with my family, acquaintances and friends.  So let me explore nine reasons why you would benefit from using Gmail.

1. Gmail is Free

One of the best things about Gmail is that it is free. I don’t have to worry about paying for expensive software to send and receive email. Nor do I have to worry about updating it. I just use the same free platform day in day out.

2. Gmail allows you to Label Messages

The ability to label messages makes it easy to sort messages according to various topics. You can literally label any message and assign multiple labels to any messages. When you hit the label any message that has been assigned a particular label appear magically in front of your eyes.

3. It Links To Other Google Services

Having a Gmail account makes it a cinch to link to other Google services like Adwords, Analytics, Reader, You Tube, Website Optimizer and Webmaster Tools. The accounts are all linked so I can access all services without having to log in to other accounts. This makes Gmail a great time saving device.

4. You Can Filter Messages

The best feature of Gmail is the ability to filter. This means that you can set things up so that only the most important emails get delivered to your inbox. The rest still arrive but get sent directly to folders where you can deal with them at a more convenient time. It is a great way to work out what emails you get sent that you rarely look at.

5. You Can Have Up To 5 Return Email Addresses

A great feature of Gmail is that you can set up a number different email accounts and run them through just one Gmail account.

For example, you can use Gmail to send and receive email as carol@yourdomain.com rather than your gmail email address.

6. Web Based Not Computer Based

My old Outlook program had accumulated thousands of emails over the years. These emails took up valuable space on my computer. Using Gmail means that everything is stored in the cloud and I don’t have to worry about storage on my computer again.

The other good thing with a web based email program is that you have a back up if things go wrong. Recently my Microsoft Outlook program decided not to work after a Windows automatic update. It took about 1 week to resolve the issue. Had I been reliant on Outlook I would have been stuffed but since I made the transition to Gmail, I could send and receive emails easily without having any major interruptions to my business.

7. Grant Other People Access To Your Email Account

Like Outlook, you can give other people access to your account so it makes it easy for other people to look after your account if you are away on holidays.

8. Voice and Video Chat

Gmail has the ability to chat online – a handy feature which you can use to either type messages or have video calls to other people who are connected online.

9. Lots of Apps

There are literally hundreds of applications that you can use to really pimp out your Gmail account. For example you can create a document from an email conversation or even add Google calendar gadgets so you can see your calendar within your email view.

Four reasons why you should have a Gmail account

For those of you who have lived under a rock for the past 20 years, GMail is the world’s top rated search engine on the World Wide Web.  They have market cornered when it comes to searching for information.  It does not matter what the information is.  Google is there to help you look op why bats are blind, how to remove warts or even the history of Tibet.  And GMail is their very own email service that uses can use for personal use.  So lets move on and discuss four reasons why you should have a GMail account.

Old people can use it and not get grumpy

Who said that only IT professionals and rocket scientist should have email access?   Sign up for a free account and start enjoying connecting with your friends and family with a few clicks of the keys.  The application is so easy to use that even the older generations will be able to get their email easily.

Hangout is cool

Whenever you log into your GMail account you will now notice the little icons in the bottom left part of the screen known as “Hangouts”.  Now uses can use GMail as a tool to connect with their friends and family instantly.  Hangouts are an instant messaging application a lot like the free AOL and Yahoo’s Messenger.  My favorite feature with the GMail’s version is that you can video chat with your friends and family individually or in a group hangout.  This means a good amount of versatility when it comes to communicating with loved ones. 

The Account Is Free

A wise man once told me that just because it is free does not mean that it is good.  Well, this is an area that I would have to disagree with.  Google provided GMail to the mass market so that everyone can enjoy the benefits of having an email account.   You do not have to have any money on hand to sign up for a GMail account.  All you need is access to a computer, tablet or a smart phone and you can get your email anywhere in the world just by logging in from your devise.

So there you have it.  Three reasons why you should have a GMail account in short order.  It is a free service that everyone can enjoy.  It is easy to use.  And finally, the extras provided will help you stay connected to friend and family.

Cisco Certified Network Associate, or Not?

So you are thinking about getting your CCNA.  You better hurry up, get off the couch and start studying.  The test is about to get a harder for those wishing to put it off after September of this year (2013). Cisco has announced that they are revamping the CCNA (Cisco Certified Network Associate) testing requirements and the level of difficulty is going to jump to what is currently the CCNP (Cisco Certified Network Profession) level.  But the question still remains, is it worth certifying in the first place.

One must do a lot of soul searching to answer that question.  And I have found that it really does depend on the individual.  I’ve been in the field for over 15 years working on both Cisco and Juniper routing and switching gear for a majority of that time.  I have learned a great deal about the inner working of the hardware and software that both providers offer.

In my case, the certifications do serve a small purpose.  They simply prove to employers that the certified applicant or professional knows the theory behind the certification.  It does not mean that they have the experience to implement, troubleshot and maintenance the networks based on their certification level.  While I’m an engineer who has years of experience, that does not mean that I have a strong grasp of the theory to do the same.

So in conclusion, I feel that a certification is a nice thing to have.  Employers like to hear that engineers and administrators have the certification to back up their experience.   So if you have the time to study for the test, I would suggest getting it done soon.  I know that I have procrastinated long enough.

Network Guy

Network Guy is alive and well - first posting

Why a network blog.  Well, why not.  I love what I do fore living and writing about what I do and what I want to accomplish in the future will help not only me to continue to grow as a network engineer.  But it will also allow me to share my knowledge in the area.

I have worked as a network engineer for a very long time.  Now that does not mean that I know everything that there is to know.  I am not an expert in my field.  I simply know enough to do my job effectively within the industry. 

So welcome to my blog and feel free to share your knowledge about anything related to Information Technology. 

If you want to learn more about me, please feel free to read up on me in the "about me" section.

Welcome and enjoy.

Network Guy