2008 IPv6 Summit: Philippines Moving Forward To IPv6
At last an IPv6 Summit will be held here in the Philippines! Thanks to the sponsors and organizers of this event, I hope that this event will increase the number of IPv6 ministers here in the Philippines. The event will be on May 21 to 22, 2008 at the Sofitel Philippine Plaza Manila, CCP Complex Roxas Blvd, Pasay City.
You can register online at http://ipv6summit.phnog.org
adduser command
In system adminstration, one of the first thing that you need to know is how to create or add a new user. It is a good practice not to use the 'root' account especially when you access your system remotely. We need to create a new user account with basic privilages and just allow this user to switch to 'superuser' whenever it is needed.
To add a new user in freebsd you just execute the 'adduser' command at the prompt but make sure you are using your root account when doing this.
# adduser (press enter)
Username: obispo (type the username to be added and press enter)
Full name: ark obispo (type the full name of the user account or you just press enter)
Uid (Leave empty for default): (just press enter)
Login group [obispo]: (just press enter)
Login group is obispo. Invite obispo into other groups? []: wheel (if you allow this account to be able to switch to 'superuser', type wheel then press enter or else, just press enter)
Login class [default]: (just press enter)
Shell (sh csh tcsh nologin) [sh]: (choose the shell you want to use or just press enter)
Home directory [/home/obispo]: (just press enter)
Use password-based authentication? [yes]: (just press enter)
Use an empty password? (yes/no) [no]: (just press enter)
Use a random password? (yes/no) [no]: (just press enter)
Enter password: (type in the password for obispo then press enter)
Enter password again: (retype the password for obispo the press enter)
Lock out the account after creation? [no]: (just press enter)
Username : obispo
Password : **************
Full Name : ark obispo
Uid : 1007
Class :
Groups : obispo wheel
Home : /home/obispo
Shell : /bin/sh
Locked : no
OK? (yes/no): yes (type 'yes' then press enter)
adduser: INFO: Successfully added (obispo) to the user database.
Add another user? (yes/no): no (type 'yes' if you want to add another user, otherwise, type 'no' then then press enter)
Goodbye!
#
Adding a new user to a group
If it so happen that you already have added a new user into your system and you want this user to be able to switched to 'superuser' mode, edit the file /etc/group using favorite unix text editor and append the username at the wheel group like the one shown below:
wheel:*:0:root,obispo
To switch from your newly created account to superuser, just type the command 'su' and supply your superuser(or root) password.
Counting the days of IPv4
Who said that the world won't need 4,294,967,296 ip addresses? Well, this might be what they thought when they designed the first Internet Protocol which is commonly known as IPv4 (RFC 791). But today, the use of IPv4 address has grown exponentially which led to a rapid decrease of available ip address. JPNIC or Japan Network Information Center has released a statement about IPv4 consumption that the pool of IPv4 address is expected to run out this coming 2010
(http://www.apnic.net/news/2007/0626.html). It may not exactly fall on 2010 but truth about IPv4 address exhaustion is presistent and it will happen 2 to 4 years from now.
Why an exponential growth? Aside from the rapid growth of Internet users, you can find IPv4 address almost anywhere now. Your GPRS enabled mobile phone has an ip address and in some part of world even automobiles and home appliances can be connected and be monitored and controlled over the internet (http://www.pcmag.com/article2/0,1759,110893,00.asp).
So what if the IPv4 reaches its end? There is no need to panic, the Internet Engineering Task Force (IETF) has already designed the Next Generation Internet Protocol 10 or 12 years ago. They call it Internet Protocol Version 6 or IPv6.
IPv6 to the rescue
This is the number of available IPv6 address the world can have 2^128. This is about 3x10^38 (340,282,366,920,938,463,463,374,607,431,768,211,456) ip addresses. Still it is a finite value though, but IPv6 architects said that this number should be enough for you to have your own PAN (Personal Area Network) in which even your underware is assigned with an IPv6 address.
How is this next generation address represented? If the IPv4 address which is 32-bit long was simplified by grouping it into octets(8-bits) separated with a dot(.) and represent each octet with its equivalent value in decimal, IPv6 address which is a 128-bit address is divided into 8 16-bit fields. The separator used in IPv6 is a colon(:) and represent each 16-bit number into a 4 digit hexadecimal value. A sample IPv6 address representation is 2001:0db8:abcd:00ef:0000:0000:0000:0001.
An IPv6 address has three categories just as we have IPv4 classes. The three categories are, IPv6 Unicast Address, IPv6 Multicast Address and IPv6 Anycast Address. An IPv6 unicast address can be used as an identifier for a single interface, an IPv6 anycast address can be used as an identifier for a set of interfaces, while an IPv6 multicast address can be used as an identifier for a group of nodes.
IPv6 Advantage over IPv4
Looking at the figures, we can directly identify that IPv6 offers a much larger IP address space than IPv4. With this, it is certain that IPv6 can be the solution of the IPv4 address depletion problem. The IPv6 address architecture is also more efficient and hierarchical than the IPv4 address. This will solve the currently increasing backbone routing table size. Lastly, IPv6 address was designed with some built-in features such as security, stateless address autoconfiguration, multicast, QoS (Quality of Service) and more.
IPv4 Overview
This is intented to give a brief review on IPv4 and discover the magic of Routing IPv4 packets then unravel the secrets of Subnetting.
Basically, the Internet Protocol Address Version 4(IPv4) has 3 different usable classes, namely:Class A, Class B and Class C. There is also a group of addresses used for multicast called Class D and another group of reserved addresses used for research called, Class E. This document will focus only on Class A, B, and C.
IPV4 Review
In order to start unraveling the mystery of subnetting, let us try first to review the characteristics of an IPv4 address. An IPv4 address as we all know is 32-bits in size which is divided into 4 groups called octets. Each octet represents 8-bits of data(4 groups x 8-bits per group equals 32, right?). In writing this 32-bit IP address, each octet is separated with a dot(.) and the leftmost octet is the most significant octet and the rightmost octet is the least significant octet.
IPv4 Address Binary Representation:
In order to be able to identify to which class does an IPv4 address belong, we look at its most significant bits(the leftmost bits) of the most signifacant octet of an IPv4 address.
In Figure 2, if you try to examine a Class A address, you will find that its most significant bit is equal to 0. The first two most significant of a Class B address is 10 and Class C address starts with 110. The x's found in Figure 2 represents either 0 or 1.
Simplifying the IP address:
Suppose we have an IP address in binary: 11000011101010100101010100001111 (32 bits)
It will be divided into 4 octets separated with a dot: 11000011.10101010.01010101.00001111
But binary numbers are hard to memorize, so an IPv4 address is commonly represented in decimal formats.
11000011.10101010.01010101.00001111 is now represented as 195.170.85.15
Binary to decimal conversion:
11000011 = 195
10101010 = 170
01010101 = 85
00001111 = 15
CCNA Practice Problems:
Q1: The IPv4 address 195.170.85.15 belongs to what class?
Q2: What could be the minimum and maximum value for the first octet of a Class A address?
Q3: What could be the minimum and maximum value for the first octet of a Class B address?
Q4: What could be the minimum and maximum value for the first octet of a Class C address?
Answers will be posted in the next blog related to this article.
To be continued...
Next topic: The Magic of Routing
I am so glad to welcome myself in the world of blogging. A human brain has around 10 billion neurons and every bit of information we acquire or gain in each clock tick is stored in our brain in a form of neuron charges and structures. This blog will be a dump site for some of my selected neuron structures which were formed in my day to day quest for knowlege.I hope that while you are exploring this vast virtual universe, you will find some of my dumps as one of your significant discoveries and will bookmark this site for future and further exploration.
