The Island of Logic

Since I am on the phone with a Microsoft Tech Support Engineer right now, I was reminded of a rather humorous Microsoft Tech Support voice mail I had heard several years ago. I searched YouTube to see if I could find it and sure enough, here it is.

This guy really doesn’t like his MAC very well.

Frankly, I am in love with Google. I can’t think of another company in the world that keeps developing new products and delivers them to the world for free. Google generates their primary revenue stream through advertising with unobtrusive text based links. Even their ads are not the huge annoying flash ads used by many other web based advertisers. Google realizes that by creating free products for the public they are simply driving more traffic to their websites and indirectly to their customer’s ads, a brilliant marketing strategy. I am going to go through the Google tools that I use the most, that some of you may simply not know exist.

Gmail I am sure almost all of you are aware of Gmail and probably use it, but are you aware of all the features and ways of using it. First I am going to show you Gmail Drive. Gmail provides more space than any other email provider out there, at least that I am aware. When Gmail first came out they promised 2 GB of space to all their users, Yahoo and Hotmail immediately increased their email capacity to keep up. Well, Google eventually went even higher than 2 GB and left the competition in the dust. Below is a screenshot of the space I currently have available in my Gmail account.

I currently have 7 GB of space available in my account. As you can see I am only using 31 MB of that space, statistically 0%. Gmail Drive allows me to use that space as remote storage. There are several advantages to this. First I can store files in my Gmail Drive and access them from any computer in the world, simply by logging into Gmail. Second if my computer hard drive fails, I have a free backup of my important files on remote storage. Awesome!!



The Gmail Drive Shell Extension is available for download at the developer’s website. (http://www.viksoe.dk/code/gmail.htm)

Gmail also allows you to download and send your email through your favorite email client, Outlook, Outlook Express, Thunderbird, etc., with secure POP3, SMTP, and IMAP protocols. Most other Internet Email services require payment for this feature. Google has some very good documentation on how to do this at http://mail.google.com/support/bin/topic.py?topic=12805.

Google Earth Google Earth lets you zoom in anywhere on earth to view satellite images of the terrain (find your own house). (http://earth.google.com/)

Google Docs Don’t own Microsoft Office, don’t want to go to the expense of buying it, want to store and create presentations, spreadsheets, and documents online in a secure way, away from that potentially faulty hard drive in your computer, then Google Docs is for you. You can even import existing Excel Spreadsheets, Word Documents, and Power Point Presentations. (http://docs.google.com/)

Google Chrome Google Chrome is the recently released web browser by Google. I like it because it is fast, has a simple and basic interface, and frankly does a better job of rendering DHTML then the beta Internet Explorer 8 browser which I am currently helping Microsoft test. (http://www.google.com/chrome/)

Google SMS Google SMS is a little known feature that Google has. It allows you to text questions to 466453 (GOOGLE), like ‘sushi 34232′ and it will send back the name, address and phone number of all Sushi locations in the 34232 zip code. Check it out. (http://www.google.com/intl/en_us/mobile/default/sms/index.html)

1-800-GOOG-411 I have used Google’s 411 service for a while now and it is great, oh yeh and free to. (http://www.google.com/goog411/

Picasa Picasa is a great photo organizing tool which allows you to make simple edits, turn your pictures into slide shows and movies, and best of all upload them to the Picasa Web Albums so that you can share them with family and friends. (http://picasa.google.com/)

Google Talk I have used Google Talk for several years now to keep in touch with colleagues, family and friends. I can talk or instant message. It also includes the previous Google Notify service which pops a message up in my tray whenever I receive a new email to my Gmail account. (http://www.google.com/talk/)

Google Search Operators Ever wonder why some people find what they are looking for in Google faster then what you can? They are probably using some of Google’s advanced operators. Here are the links to Googles operator pages

http://www.google.com/support/bin/static.py?page=searchguides.html&ctx=basics&hl=en

http://www.google.com/help/operators.html

Using these operators can reduce the amount of pages that you have to search through to find what you are looking for. For example, searching for the string “let them eat cake” with the quotes will likely produce more of the desired results then searching for the terms without quotes. Using the advanced operators for example I could search the www.yes941.com website for the search terms ‘John Greer’ using the following search term “site:www.yes941.com John Greer“. You can also use the Google Advanced search page which makes the use of some of the advanced operators easier. (http://www.google.com/advanced_search)

For a list of many more Google features not mentioned here go to the following link. (http://www.google.com/intl/en/options/)

Here is a video that I used to show my students, to demonstrate how social engineering was accomplished. This video has Kevin Rose the former host of the TechTV show. Now some of the actions on this video are illegal and should not be attempted on your own, :) however this does not give a detailed view anyway on how to compromise a computer network. It is funny and interesting to watch though.

I don’t usually listen to NPR :), but a friend of mine sent me a link to a segment of the Diane Rehm Show that he heard on NPR. I listened to the segment and it is very good. Diane interviews Paul Kurtz, Alan Paller, Stephen Spoonamore, and Congressman Jim Langevin. They discuss the Cyber Security Threats that exist from sources like China, etc.. This is a 50,000 ft. view that can be understood by anyone, and does not contain all the technical jargon usually part of Geek Shows. This is enlightening to anyone that wants to understand more; what threats exist to their personal Internet security.

Link to Segment on the Diane Rehm Show

I have decided to publish this article again. I had posted this on the Internet about 4 years ago so that the students in my networking classes would have something to reference back to after I addressed the subject in class. I am going to post the article here again along with a video explaining IPv4 addressing (coming soon). I will post another article soon delving into the details of IPv6. This article here covers the decimal and binary math related to IP addressing and Subnet Masks. A well rounded knowledge of these concepts is critical for network engineers to know in order to design networks and implement security.

Ok, lets start out with a definitions of the terms. If you already know these, then good for you. These are my own definitions and formulas, not copied from anywhere. Please do not use these without giving credit, or gaining written consent.

TCP/IP: Transmission Control Protocol/Internet Protocol
Decimal: A numbering system with values from 0 to 9. Ten possible values. Also known as Base-10.
Binary: A numbering system from with values from 0 to 1. Two possible values. Also known as Base-2.
Bit: A single value in the binary system. Either a 1 or a 0.
Boolean Logic: A combinatorial system that uses the operators AND, OR, NOT, and XOR. Boolean logic can have one of two values true or false.
IP Address: The decimal representation of the binary value of the number that identifies a node on a network. A 32 bit number. I.E. 192.168.4.12
Broadcast: A network transmission that is sent to and processed by all the nodes on a subnet.
Multicast: A network transmission sent to and processed by group of nodes in a subnet.
Unicast: A network transmission sent to and processed by a specific node in a subnet.
Node: Anything that can have a IP address assigned to it.
Subnet: A mathematically segmented number of IP addresses that are on the same logical network (It does not have to be the same physical network, though it often is. Because of this it is sometimes confused with the ethernet contention domain.)
Broadcast Domain: All the IP addresses that receive the same broadcasts. Also a subnet.
Network ID: The decimal value of the ANDed IP address. Also the base value of the subnet. Always has the value of all 0s in the Host ID portion of the IP address.
Host ID: The portion of the IP address as defined by the subnet mask that identifies the node in the subnet.
Broadcast ID: The last IP address in a subnet. Cannot be assigned to a node. Is used for broadcast transmissions. Always the value of all 1s in the Host ID portion of the IP address.
Subnet Mask: A decimal representation of the amount of bits used to define the Network ID. I.E. 255.255.255.128
CIDR: Classless Inter Domain Routing. A shorthand method of defining a subnet mask. States the number of bits used to define the Network ID. I.E. 192.168.4.12/26 (the /26 is the CIDR notation)
Octet: A IP address is divided into four sections separated by decimal points. A section is called a octet. This is because it has eight binary bits.
Gateway IP address: The IP address that identifies the node that receives transmissions that are being sent to nodes that are not in the sending node’s subnet.
Integer: Whole numbers. Numbers without fraction or decimal. For example the integer of 2.67 would be 2.
Modulus: The simplest way to describe this is to say the remainder of a number divisable by another. In other words 8 mod 3 = 2. The remainder of 8 divided by 3 is 2.

Formula Variables:
A = Amount of Nodes
H = Host ID Bits
0 = Octet Value
N = Network ID
B = Broadcast ID
C = CIDR
U = Octet value counting from the left that is the value of “O”.

The math behind figuring out IP subnets is simple and can be done in your head as soon as you understand the concepts. It is just a conversion from binary to decimal. Below I have a chart with the math behind figuring the amount of nodes supported by a Subnet Mask. This covers subnets smaller than 255.255.255.0, but the math works the same for the larger subnets. Now let’s get into the math behind the madness. Let’s start with the formula for calculating the Octet (O) from the left that is the one to be used in the following Amount of Nodes equation, the formula is INT( C / 8 ) + 1 = U. This tells the Octet value, counted from the left that will populate O. Now to calculate the Amount of Nodes. Take 2 to the power of the amount of Host ID Bits multiplied by 256 to the power of 4 – U and then subtract a final 2 values for the Broadcast and Network ID since they are not addressable IPs, and the result will give you the amount of Nodes, so our formula is (2^^H) * 256^^(4-U) – 2 = A. Host ID bits is calculated by subtracting the CIDR from 32 (The amount of bits in a IP address) and a modulus of 8 (The amount of bits in a single Octet). So our formula for Host ID bits is (32 – C) mod 8 = H. So lets take the IP address and subnet of 192.168.12.129/26 and lets calculate the amount of nodes. We need to first get the Host ID bits so as in the previous equation we subtract the CIDR from 32 with a modulus of 8. That would be 32 – 26 which is 6, then 6 divided by 8 with the remainder of that division being 6, so our answer is 6 Host ID bits. Next we use the amount of Nodes formula (2^^H) * 256^^(4-U) – 2 = A. This would be (2^6) * 256^^(4-4) – 2 = 62, or in words, 2 to the power of 6 multiplied by 256 to the power of 4 minus 4 and then a final 2 values are subtracted for N and B since they are not addressable and the result is 62, so 62 is the amount of Nodes we can have in that subnet.

Subnet Masks and their corresponding Node ranges:

Ok, now that we see that calculating the amount of Nodes is easy lets look at the formulas for calculating the Network IDs and Broadcast IDs. Lets use the same IP address of 192.168.12.129/26. The CIDR is 26 so remember our previous formula for calculating the Host ID bits (32 – C) mod 8 = H. So lets do it again, 32 – 26 mod 8 = 6 Host ID bits. Now for the formula for calculating the Octet (O) from the left that is the one to be used in the following Network ID equation, INT( C / 8 ) + 1 = U, so in this case since the CIDR or C value is 26 the formula would read like this INT( 26 / 8 ) + 1 = 4, or in words, the integer of 26 divided by 8 which is 3 plus 1 equals 4. That means that the Octet value to populate O will be 129, the 4th Octet from the left. Ok, now lets use the formula for calculating the Network ID (Int(O / 2^^H)) * 2^^H = N. Lets work through it, the integer of 129 divided by 2 to the power of 6 equals 2, or the integer of 129 divided by 64 equals 2. Then the rest of the formula is 2 multiplied by 2 to the power of 6,  or 2 multiplied by 64 which equals 128, so our Network ID is 128. (Int(129 / 2^⁶))*2^⁶ = 128. Ok, now lets calculate the Broadcast ID. Now the entire formula for that would be (Int(O / 2^H))*2^H + (2^H – 1) = B, but since we already know the Network ID we can simple do N + (2^H – 1) = B. Lets work through it, 128 + (2^6 – 1) = 191, or in words, 128 plus 2 to the power of 6 which would be 128 plus 64 minus 1 and that equals 191. Ok then, our broadcast is 191. Lets see all the results of 192.168.12.129/26.

Network ID: 192.168.12.128
Broadcast ID: 192.168.12.191
Amount of Nodes: 62

Formulas:
H = (32 – C) mod 8 (Excel formula “H = mod( 32-C,8 )”)
A = (2^^H) * 256^^(4-U) – 2
U = INT( C / 8 ) + 1
N = (Int(O / 2^^H))*2^^H
B = (Int(O / 2^^H))*2^^H + (2^^H – 1) or N + (2^^H - 1)

These formulas work fine in Excel so you can simply copy and paste them in if you like. Obviously you will have to replace the variables with cell numbers, but that is a given.

So now you are going to say, how do I calculate the CIDR if all I am given is the subnet mask? I thought you might ask. I considered demonstrating this with a rather complicated equation, but I think a chart will simply be easier to use and remember. Remember that a subnet mask is simply the decimal representation of the amount of bits used by the Network ID. The boolean AND logic is used by the TCP/IP stack to AND the IP address against the subnet mask and the result is the Network ID. The subnet mask of 255.255.255.192 converted to binary would be 11111111.11111111.11111111.11000000. The CIDR is simply a count of the amount of bits from the left that are used to define the Network ID. If you notice the first, second, and third octets are all 1s since the binary value of 255 is 11111111, so all 8 of the bits are used for the Network ID in each of these octets. The last octet is 192 and the binary value of that is 11000000, so there are 2 bits used in this octet for the Network ID. So you can simply count the amount of 1s to get the CIDR or do 8 + 8 + 8 + 2 = 26 and that is the CIDR. To get the CIDR just use the chart below and add the bits for Network ID together to get the CIDR. I.E. The CIDR for 255.255.240.0 would be 8 + 8 + 4 = 20.

Subnet Mask Decimal and Binary Equivalents:

It has been my opinion for sometime now that if a network engineer is incapable of performing these simple functions in his head, then he should look for a job elsewhere. The reasoning behind that is if they are not able to perform this simple task what other essential networking tasks are they not capable of. General networking theory knowledge is so lacking today; sometimes I wonder how some people are capable of performing their jobs (Google is good). I have some fellow engineers that disagree with me on this opinion, you can guess who they are. :)

This is so funny. This was emailed to me by a co-worker. Admittedly the language is a little rough, don’t watch if you are easily offended. This is so typical if you are a IT guy though. This guy does some classic moves like deleting your boss’s sent email so that you can claim he never sent an email to you. Setting a user’s desktop background to a picture of their desktop and then deleting all their icons. He used the same method that I used when I was a network admin to users when they would call. I would ask them if they had rebooted their machine even if it was something as simple as a missing icon or something. Another classic move is to use VNC or something similar to get into a user’s desktop while you are on the phone with them, and asking them to login. You can kindly add some additional characters while they are typing their password. You then berate them for their typing skills or their stupidity for forgetting their password. This will always bring laughs to anyone in the IT Dept. Granted it probably does not improve relations between IT and users, but it sure is funny.

This Video was create by Website is Down: http://dpt.thewebsiteisdown.com/dpt/

I think it is great that Microsoft provides a limited edition of their kernel free for a Pre-boot environment. It is a great troubleshooting tool. Microsoft has provided the PE disk since Windows XP, but it was at one time only available to OEM’s. This disk will work with all versions of Windows and even other OS’s, as long as it has a file system that is readable by Vista. I just got done using a PE disk on a unbootable machine (wouldn’t even finish loading in Safe Mode) at a customer to restore the registry from a System Restore point. Works like a charm.

Below are the instructions on how to create a Windows Vista PE disk.

• Download and install the Automated Installation Kit from Microsoft. (http://www.microsoft.com/downloads/details.aspx?FamilyID=C7D4BC6D-15F3-4284-9123-679830D629F2&displaylang=en) 
• Open the AIK Command Prompt. Start Menu>All Programs>Microsoft Windows AIK>Windows PE Tools Command Prompt.

• Next you will use the “copype” command to create the Win PE structure based on the processor architecture that you have, x86 or AMD64. In this case I am using the “copype x86 c:\windowspe-x86″ command.

• The resulting output of the “copype” command will generate a folder structure under C:\windowspe-x86. In this folder will be the necessary files to make a bootable ISO file or a WIM image file that can modified and deployed with ImageX. In this case we will just create a bootable ISO image file.

• The command that can be used to generate the ISO file is “OSCDIMG -bc:\windowspe-x86\etfsboot.com -n -o c:\windowspe-x86\iso C:\windowspe-x86\win_pe.iso”. The -b option specifies the path to the file containing the boot sector. The -n option allows file names longer then the DOS 8.3 format. The -o option is used to optimize the amount of space used by encoding duplicate files only once. The command will generate a bootable Windows Vista PE disk in the C:\windowspe-x86\win_pe.iso location. You can then burn this ISO to CD using any of your favorite CD burning software packages, like Nero, Roxio, etc.