Home Lab Concepts

Can hardly believe I am almost ready to graduate. The last three semesters have been a blur and I am sure if you think its all summed up in the several blog posts so far that it probably was but alas I assure you that working full time and studying has left me little time to post.

This however excites me to much to keep it to myself. I have finally taken the initive to draft and build a home IT lab that will allow me (and a select few who pay tribute in the way of pizza and Mt Dew) the ability to perfect the things we have learned thus far with hands on practice that dont involve driving to the campus lab everytime we need a hacker fix.

The foot notes on this I think are self explanatory but long story short its designed to practice for certification (CCNA, MCITP, LINUX+) and also be fully scalable to grow as I head into the advanced program later this year.

If anyone happens upon this and wants to comment feel free to chime in on the comments (you will be the first). Right now time is against me but I have all the equipment at my house and as soon as spring break hits and my vacation from work starts you better believe I will be wiring this bitch up.

Pics will follow when I am done. Hope you enjoy.

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VTP Modes Explained

My days in semester 3 of the Cisco Networking Academy are drawing to a middle, in just a few hours I will have to take a midterm skills final that will test my knowledge of the Cisco VLAN Trunking Protocol (or VTP), so before I jump into that I will lay down what I have learned here.

VTP is Cisco propritary, Juniper and other switches might have equivlent commands but VTP only works on Cisco equipment. VTP basically advertises and synces information regarding VLANS to all switches on a network or to be more thorough, all switches in the same VTP domain.

SWITCH(config)# vtp domain YOURDOMAIN

Cisco switches running VTP can be configured into one of three modes (that I know of so far) and they are; server, transparent, and client.

SWITCH(config)# vtp mode server

This is the default VTP mode. A VTP domain must have atleast one switch configured as the VTP server so that information regarding VLANs can be propagated to other switches in the domain. On a server you can create, add, edit, and delete VLANs. Any of these changes are sent out to other switches on a VTP domain.
SWITCH(config)# vtp mode transparent

Switches running in transparent mode are said to not participate in the domain, and while that is technically correct they do play a part as a forwarding device between server switches and clients.
SWITCH(config)# vtp mode client
Client switches listen for updates from other switches via VTP advertisements and update their VLAN configs accordingly. This is dependent on a connection to a switch running VTP server mode. Also it is not possible to create, add, delete or edit VLANs on the client.

This is just the very tip of the iceburg regarding VLANS. I have to say that semester 3 cisco is by far the most interesting instruction I have had to date. The content is well writen and presented very clearly, where at times transparent concepts from previous semesters (such as how different routing protocols achieve network convergence) were clear as mud. Love this class, learning alot, wish I had time to write more.

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Default Router Passwords

Had to look look up stuff here more than once.


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Turning Off Interface Messages on The Cisco IOS CLI

I have been exposed to Cisco routers for some time now. Something that has always bugged the hell out of me is that every time an interface farts, coughs, or burps the IOS by default floods the CLI with the interfaces thoughts and feelings and consequently causing you to possibly slip up a command.

no logging console tells the interfaces in the back seat to shut up all together and let you drive the router. Some people have a problem with this and I can see how you might miss some important information regarding interfaces and overall connections in general but I find that if (and I hope your not forgetting to) check the interfaces and config before saving it to make sure everything is up and running then you probably wont miss anything important.

logging synchronous  lets the router express it's feelings about your relationship and complain about the other routers and not cut you off when you are entering network addresses by moving the input cursor down a level to make room for the routers complaining. It's the command that most admins agree on I guess, and is probably the option Dr Phil would choose if he were in this business.

I for one hate those updates, have found them more annoying than informative, and prefer to turn them off all together. Well, back to packet tracer labs. Just needed to vent.


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Windows 7's Use of Virtual Environments to Support Applications

As I get ready for the Microsoft 70-680 I just wanted to share something that really impresses me about the way Windows 7 supports different applications. It does not allow every program and its strings access to the physical kernel, instead multiple VDMs are created based on the type of application being run.

Win32 Applications – Most common type of application used with operating systems like Windows XP. Becoming less popular as .Net replaces it. Each Win32 application runs in its own virtual memory space and is executed by the processor in user mode. If the Win32 application crashes, it will not affect other Win32 applications or the operating system's kernel Executive services.

Net Applications – The new preferred way for applications to access the operating system service. The .Net Framework provides a layer of abstraction that is useful for developers to perform complex tasks more simply because the .NET framework manages the details of accessing required services. Developers should create new applications by using the .NET framework not only to simplify development, but also to ensure compatibility with future operating systems. Future versions of Windows may not support Win32 applications. However, the .NET framework 3.0 isolates applications from any change to the Win32 subsystem.

DOS Applications – 32bit versions of Windows 7 support the execution of legacy DOS applications. A special Win32 process called ntvdm.exe creates a virtual DOS machine (VDM) environment for that DOS application. Ntvdm.exe and the Win32 subsystem control the applications access to the host computers hardware. Full screen support in these applications are not available in Windows 7.

Win16 Applications – ntvdm creates a virtual environment to run 16bit programs that were once compatible with Windows 3.x. Where as DOS applications get their own VDM, only one is created to handle Win16 apps. This is an instance of ntvdm.exe and an application called wowexec.exe. Wowexec.exe is part of the Windows 7 operating system and supports Win16-on-Win32 execution. Since these apps run on the same VDM, a single program crashing can wipe out all other Win16 apps. While this is the default setting, you can change it to allow all Win16 apps to have their own VDM.

x64 Application Considerations – This is a VDM for x64 versions of Windows 7 that can support 32bit applications with a Win32-on-Win64 (WOW64) virtual environment.
DOS and Win16 apps are not supported.

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