Implementing Network Infrastructure – 9/30/2008

Welcome back, all uhm one of you! (Ok, actually the second one of you came in the afternoon, and I knew about it beforehand, etc.)

DHCP was the topic of the day.  Remember back in A+ and Net+ when we discussed DHCP as the squeaky-annoying guy that called out and whined until a DHCP server heard him and shut him up.

Well today, we actually dissected the “little whiney guy” into what actually happens with DHCP client and server communication, and it turns out that our DHCP clients and servers only know how to say eight different things to each other:

• DHCPDISCOVER - this is the initial broadcast blast spewed out by the DHCP client in search of a DHCP Server.  If a DHCP server does not answer this DHCPDISCOVER packet with a DHCPOFFER packet, then the DHCP Client self-configures with an APIPA address, which belongs in the 169.254.0.0/16 network (non-routable, by the way).
• DHCPOFFER - If a DHCP server detects a DHCPDISCOVER packet out there, it replies back to the client with this DHCPOFFER packet.  Effectively, this is the server saying, “Hi, I’m a DHCP server.  Would you like me to send you configuration information?”
• DHCPREQUEST - Once the client receives a DHCPOFFER packet it sends the DHCPREQUEST packet back to the server.  It’s the client’s way of answering, “Yes, thanks!  Can I have some configuration information please?”  This may seem confusing, but it makes a lot more sense when the client goes to renew its configuration.  More on that later.
• DHCPDECLINE – This packet is sent from the DHCP client to the DHCP server when it does not want configuration.  This might happen if a DHCP server answers a client’s DHCPDISCOVER packet after another DHCP server has answered it already.
• DHCPACK - When a client accepts configuration settings sent by the server, the server acknowledges it by sending this packet.
• DHCPNACK – This packet is sent by the server whenever the server wants to invalidate the client’s configuration.  “You are not acknowledged, client.”
• DHCPRELEASE – This command is issued by the client to release itself from configuration.
• DHCPINFORM – In some instances, it’s possible that a NIC will want to obtain more than one set of configuration.  If that’s the case, the client sends a DHCPINFORM.  It’s the equivilent of asking for a waitress to bring an entire pitcher of beer instead of just ordering them one at a time.

Now that I’ve pretty much published the entire lexicon for DHCP machines, let’s look and see how some of the conversations actually flow.  First of all, let’s look at a brand new computer being turned on for the first time in a subnet with one DHCP server:

1. The client sends out a DHCPDISCOVER packet.  “Hey, is there anyone here who knows how to configure me???”
2. A DHCP server hears the cry and responds back with a DHCPOFFER packet.  “Hi, I’m a DHCP server.  Here is some configuration information…”
3. The client accepts the information by sending the DHCPREQUEST packet.  “Thanks!  Can I have that configuration information?” (This seems redundant to us as human beings, but it happens.)
   
4. Once receiving the DHCPREQUEST packet, the server responds back with a DHCPACK packet, acknowledging that yes, this particular client has an IP address.  At this point, the DHCP database is updated with the MAC address of the client tied to the given IP address, and the IP address is taken out of the possible pool of addresses.
   

Then, the client is free to roam the network with their set configuration information.  The configuration has an expiration date however — it’s called a lease.  And just like responsible apartment dwellers, the client tries to renew its lease long before it’s up.  Here’s what the lease renewal conversation would look like:

1. The client sends a DHCPREQUEST packet, again saying “Thanks!  Can I have that configuration information?” Here, the client is asking to keep the information.
2. The server sends back a DHCPACK packet saying, “Yes, yes you may.”

Homework:

• Chapter One Review Questions
• Chapter Two Review Questions
• Remember professional dress next week!!!

Network+ – 9/29/2008 (night)

Tonight’s class largely mirrored the day class.  We discussed a wide variety of topics including topologies and what various pieces of hardware do.  Specifically we talked about these:

• NIC: Network Interface Cards.  Without one, there’s no way you can interface with the network (duh).  Each NIC has its own MAC address, which works like a VIN number does for your car.  At the end of the day, any networking method ultimately searches out MAC addresses and delivers network packets to them.
• Repeaters/Hubs: A repeater is dumb, and a group of repeaters can only be dumber: The Hub.  Hubs take signals they receive through any one of their ports and vomit them out to all of the other ports on the hub (including yes, the originating port).  The result is a bogged down network (especially if you stick a hub on a switched network!!!)
• Bridges/Switches: Give a hub a notepad and take away its ADD, and you have a switch, which is a collection of bridges.  Bridges pay attention and can be configured to point to certain MAC addresses.  The great things about switches is that they can direct traffic to where its going without bothering nodes who aren’t interested.
• Gateways/Routers: A gateway is simply a way out of your LAN.  If you’re sending packets to a computer that’s located outside of your immediate area, it must go through a gateway, or a router.

Homework:

• Chapter One Review Questions
• Study for quiz over Chapter One
• Professional dress next week!!!

Troubleshooting – 9/29/2008

We opened the Troubleshooting class (a fun class to teach) today with an attended installation of Windows XP.  An attended installation is simply one kind of installation we can do for Windows, we can also do a network install and an unattended installation.  The network installation works how you might think, the files are delivered not by installation CDs like most of us are used to, but delivered over a network share.  This is supremely beneficial because instead of having an administrator present to input information, or even a flunkie present to swap disks, we can have someone turn on the computer and walk away.  It’s truly beautiful stuff.

The unattended installation is much less hands-on but, as I indiciated earlier, it does require a flunkie.  The unattended installation runs from either a network share or a CD, but it needs a certain file on a floppy disk named winnt.sif.  (This is why I insist on including floppy disk drives for clients I work with — I spin it as having a way for their users to transport data without a flash drive… anyway…).  You can create the winnt.sif file yourself using Notepad, or you can use the Setup Manager program included in the Support Tools directory of your setup disc to create it with a Wizard.  We did the latter and created an install file that we’ll use next week to launch a (hopefully!) unattended installation of Windows XP.

Homework:

• Chapter One: Review Questions
• Chapter Two: Review Questions
• Study for quiz over Chapters One and Two
• Professional Dress next week!!!

Network+ – 9/29/2008 (morning)

Today we launched into our Network+ class by covering the first chapter of the book, dealing with (as its title suggests) networking essentials.

We talked about various components of that including, perhaps most importantly, at least for tonight, the differing networking topologies.  We have four physical topologies and 2 logical topologies.  Make sure you know each of them (bus, ring, star, mesh in the physical realm; star-bus and star-ring in the logical realm).

Homework:

• Chapter One Review Questions
• Prepare for Chapter One Quiz
• Start wearing professional dress next week!!!

Welcome!

Hi, and welcome to my blog!

This blog will allow you to keep up with what’s going on in class this quarter. I plan on making brief posts after each class which will summarize what we’ve done that day and list any assignments I may give. That way, if you’ve missed class or need to review, you can come here any time day or night and see what you’ve missed.

I’ve designed this blog to be a tool — an extension of me outside the class, if you will. On this blog, you will find Powerpoint slides (if applicable), links to stuff I think you should know, and some links to some stuff I just think is cool. I’d recommend adding this site to your Favorites and checking it often — it’s the ONLY venue I’ll ever assign extra credit (and it does pop up from time to time).

Be sure to check this page often! You’ll never know what kinds of good things will pop up here (extra credit has been known to rear it’s quite-attractive head here from time to time).

Please leave a comment below! I love getting comments…

Managing Network Environment – 9/15/2008

Over, out.

Homework:

• Rock out with your uhm, router, out.

MS Exchange – 9/15/2008

Just a slow lazy day, hanging out…  Very happy that no one had to take the final!!!

Homework:

Enjoy the break!

Marketing – 9/10/2008

Today we officially finished up by taking our final exam.

Thank you for being such a fun class!  I enjoy the opportunity to get out of the “geek room” every now and then and you guys definintely were a group I would look forward to discussing stuff with.

Have a great time off, and I’ll see you around in the halls!

Pro/Server – 9/9/08

Happy 9/9.

Today was simply a day to take the final.  And that’s it.

Homework:

• Enjoy the next few weeks off, and come back ready to go with the Implementing classes in the fall.

Managing a Windows Environment – 9/8/2008

Ok, I’m thinking that I’m a total pessimist or something.

Tonight was the night we set aside to take the final, and once again, I was extremely pleased with the results you guys, my students, came up with.  Either I’m being an effective teacher (maybe) or I just need to recycle my tests (more likely).  Either way, fantastic job!!!  You scored some of the highest grades this course has seen in the last couple of years I’ve taught it.

Homework:

• You’ve freakin’ made it.  Go out and celebrate and kick tail in those IT careers! 
• Enjoy the next few weeks, and then get back into studying!  I want to see certs!