IPv6 Addressing

IPv6 Overview

Currently, the last of the IPv4 address blocks has been distributed and the internet is being slowly transitioned to IPv6. As a consequence, both professional networkers and networking students alike need to learn the details of IPv6 and begin configuring IPv6 enabled networks. In fact, there currently is a second internet, an  IPv6 Internet, where IPv6 is being implemented by governments, ISPs, and large organizations like Google.

 IPv6 Fundamentals LiveLessons: A Straightforward Approach to Understanding IPv6

What are the benefits of IPv6? First off, the IPv6 address space is a LOT longer than the IPv4 address space which means it will not run out of addresses like it did with IPv4. Here are some of the other IPv6 benefits:

• A simplified network prefix with no subnet mask required
• No reserved network addresses and broadcast addresses like with IPv4
• No DHCP server is required because hosts can autoconfigure their IPv6 and gateway address by soliciting network information from the router through router solicitation (RS) and router advertisement (RA)
• IPv6 has a simplified header improving efficiency and forwarding performance
• IPv6 has support for security platforms like IPsec and mobile IP
• IPv6 improves network performance by eliminating excessive network broadcasts by replacing broadcast addressing with more efficient multicast addresses

If you want an incredible resource for learning IPv6 visit Rick Graziani’s IPv6 resource page everything I know about IPv6 I have learned from Rick.

IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6

IPv6 Address Structure

The IPv6 address is 128 bits long, written in hexadecimal notation separated by colons every 16 bits (see below). For the sake of abbreviation and simplification, leading zeros can be omitted and multiple 16bit sections of zeros can be replaced with a double colon (::). The double colon substitution can only be used once in the address.

Complete 128bit IPv6 address:  2001:0DB8:0001:2F00:0000:0000:0000:0000 /64
Abbreviated IPv6 address:  2001:DB8:1:2F00:: /64

The slash notation at the end of the address, in decimal format, identifies the number of bits, counting from left to right, that make up network prefix in the address. In the example below, the IPv6 address has /64 at the end, so the first 64 bits, the network prefix, is highlighted in red (see below). Remember that each hexadecimal character is base16, which is equivalent to 4 bits.

The network portion of the address and prefix highlighted in red: 2001:0DB8:0001:2F00:0000:0000:0000:0000 /64


Video Tutorial

In this video, I demonstrate IPv6 inter-network communication. IPv6 routing is configured on an 1841 Cisco router and also on two host PCs.

Subnetting PT Network Challenge

Subnetting with Packet Tracer Overview

Packet Tracer is a great network simulation tool that is made available to Cisco Academy students. It is ideal for quickly testing networking concepts and learning. In this Packet Tracer Skills Assessment (.pka) you will need to subnet a network into 7 subnet address ranges, configure the network devices and hosts with those addresses, set up static and default routes, and set up HTTP and DNS services on a host server.

If you have Packet Tracer 5.3.3  you can download, extract, and run the zipped .pka file below. Read the built in instructions. When you have finished configuring the network you should be able to ping the server from the PC hosts as well as open the www.cisco.com web page from host PC0 or PC1s simulated web browser.

In the activity you will need to create the following 7 subnets from the /22 network address range:

1st subnet 400 hosts,
2nd subnet 180 hosts,
3rd subnet 40 hosts,
4th subnet 18 hosts,
5th subnet WAN Point to Point (4 hosts),
6th subnet WAN Point to Point (4 hosts),
7th subnet WAN Point to Point (4 hosts),

Screenshot of configure_the_network.pka activity




Application Layer PT Server Activity

Application Layer – Server Activity Overview

It is important to know the basic functions of the various networking programs that operate at the Application Layer. The average person uses these Application Layer programs on a daily basis without ever wondering about how they fit into the layered networking models of the OSI and TCP/IP models. These Application Layer services continue to be important as we learn about how they correspond to source and destination port numbers within the Transport Layer header. 

Cisco Packet Tracer Activity

Set up the following services on the servers in Packet Tracer: DHCP, DNS, HTTP (Web), FTP, and Mail. If you configure everything correctly you should be able to: receive ip addressing to the DHCP clients from the DHCP server, resolve domain name requests from the DNS server, successfully receive requested web pages from the web server, upload and download files after logging into the FTP server, and send and receive email to and from the mail server. Here is a rough outline of the steps involved:

  1. Physically connect all of the devices with appropriate cables,
  2. Configure IP addressing on all of the networking devices (follow the device labels),
  3. Configure the server services on the devices as listed (dhcp, dns, mail, web, ftp),
  4. Verify that all of the configured services work by testing from the client computers,
  5. Note: In this Cisco PT activity the services and testing do not extend beyond the LAN i.e. router.

Download the start file here: PT_working_w_servers_begin.zip ,
the finished version is here: PT_working_w_servers_end.zip
Packet Tracer version 5.3.3


Video Tutorials

Cable the network, configure IP addressing, and DHCP services

Configure and test HTTP and DNS services

Configure and test the FTP service

Configure and test Mail services

Cisco IOS and CLI


For the Cisco CCNA you are required to know how to configure Cisco routers and Cisco switches using the command line interface or CLI. A command line interface is a command driven user shell that allows the user to interface with the operating system. The command line interface or CLI is operated with just a keyboard. In contrast a graphical user interface or GUI is an icon and menu driven user shell characterized by the use of a mouse in addition to a keyboard. The Cisco operating system, used with Catalyst switches and integrated services routers is known as the Cisco IOS, or Internetwork Operating System.

  • RAM (temporary memory) – The IOS and the config file are loaded and run in RAM when the router boots up, but they are typically saved or stored in FLASH (IOS) and NVRAM (startup-config). The routing table is run from RAM. Routers and switches execute everything in RAM which is why they are so fast. Configuration changes are immediately executed in RAM (running-config) but can be saved to NVRAM (startup-config) to be made permanent.
  • FLASH (permanent memory) – This is where the IOS is saved
  • NVRAM (permanent memory) – This is where the startup-config file is saved
  • ROM (permanent and unchangeable) – This is where the BIOS, POST, and ROMMON are stored.

The IOS and CLI

The Cisco IOS is the Cisco operating system. The IOS is specific to the Cisco device it was designed for, having different capabilities and tools included in it. In this way, the Cisco IOS comes in many different sizes, capabilities, specifications and revisions.

As part of the Cisco IOS, the CLI or command line interface is included on every Cisco device including, Cisco routers, switches, and wireless access points and bridges. Most Cisco devices also have a GUI or graphical user interface. The focus of the Cisco CCNA is learning the CLI, command line interface. The command line interface is an administrative interface used to configure the Cisco device. There are three ways to access the CLI:

Console – the console port is a direct serial connection using a console/rollover cable attached from the Cisco device’s console port to a computer serial port. Usually the initial method of configuring a router or switch, because it does not rely on networking being enabled. A console connection is also how you would recover a router with a deleted configuration file, IOS file, or forgotten password.

Telnet or SSH – the ability to telnet or SSH into a Cisco device is a remote administrative connection that can also be done from the local network. In order to telnet or SSH into a Cisco router or switch you will first need to bring up a network interface by configuring it with an IP address, subnet mask, and issuing the “no shutdown” command .

Aux – The auxiliary port is designed to connect to a modem. It is used for a dial in connection to the router or switch. This remote administrative connection can also be done locally.
The CLI has different command modes, with specific commands available in each mode. The different command modes are:

  • User exec mode – Only a few commands are available in this mode. Commands like “ping”, a few of the “show” commands
  • Privileged exec mode – All of the User exec commands plus all of the “show” and “debug” commands
  • Global config mode – Access to all of configuration commands and addition configuration modes
  • Global sub configuration modes – interface configuration mode, router configuration mode, etc.


  • Router>enable
  • Router#configure terminal
  • Router#show running-config
  • Router#show startup-config
  • Router#show version
  • Router#show flash
  • Router#copy running-config startup config

CLI Video Tutorials

In this video, I cover some CLI basics

Configure console and VTY ports for administrative access

Configure enable password, enable secret, service password-encryption, and banner motd

Configure a switch for telnet access

Backup a configuration file and IOS bin file to a TFTP server

 Restore a configuration file from a TFTP Server

Restore a startup-config file from text file

Basic switch configurations including an interface VLAN1 IP address for telnet access

How to make a straight through Ethernet cable


The ability to make a straight through Ethernet cable can come in handy, whether you need to create a specific Ethernet cable or you need to fix an existing one. You can save money by making your own Ethernet cables in the exact lengths necessitated by your network. With some practice and following the standards laid out by the EIA-TIA, your cables will work nicely and be of a professional quality. In the lab below, I outline the materials and steps necessary in creating a straight through Ethernet cable.

What you will need:

  1. Cat5e Ethernet cable – I recommend purchasing a box of Cat5e cable. You will save money by purchasing your cable in bulk.
  2. RJ-45 connectors
  3. Crimper Tool – capable of crimping 8 wire (RJ-45) and 6 wire (RJ-11). Most tools have built in cutters too.
  4. Stripper Tool
  5. Scissors – I prefer using a scissors
  6. Cable Tester – For testing that your cable connections are good and there are not any open or crossed wires
a scissors, a crimping tool, and a stripping tool

cable testers

 Cat5E Ethernet cable and RJ-45 connectors

Steps to make a straight through Ethernet cable:
  1. Cut a piece of cable to the length you will need. Give a little extra to make room for mistakes.
  2. Strip a half inch to an inch of the outer jacket away from the cable. If you use strippers make sure not to nick the wire pairs and expose the copper, this could introduce crosstalk onto your wires. I prefer to use a scissor and my fingers to tear away the jacket. Then I cut with the scissors to clean up the edge.
  3. Now you need to untwist the wire pairs (not too much, only undo one or two twists) so you can align them according to the EIA-TIA568B wire color sequence. I use my fingers to straighten the wires by bending them back and forth, straightening them as they warm up.

    EIA-TIA 568B Standard

    1 2 3 4 5 6 7 8
    white/orange orange white/green blue white/blue green white/brown brown
  4. I usually have to trim the ends of the wires so they line up and create a straight edge.

  5. Now holding an RJ-45 connector with the tab side facing down, push the 8 wires into the connector, sliding each wire into a groove. While holding the connector tab side down the white/orange wire should be on the far left and the brown wire should be on the far right. It is very important that the wires push all the way up and into the connector so that when the pins are pushed down during crimping they will make contact with the wires. The sleave or jacket of the cable (light blue below) should also be pushed in as far as it can go so it will be held in place once crimped. You may want to pull the wires out and put them back in to make sure they are sliding in correctly, this will also further straighten the wires.
    notice the tab make sure it is facing down push the wires and sleave into the connector

  6. Before crimping, examine the cable and connector from the side. Did the wires slide all the way up in to the proper grooves? Are the colors in the proper order when observed from tab side down? Did the jacket slide all the way into the connector? If not, you may need pull the cable out of the connector, trim the wires or the jacket accordingly, and reinsert.
  7. If everything looks good, using your crimper tool insert the connector and cable into the 8 wire slot and press down tightly. This will cause a piece of plastic in the connector to press down on the jacket and hold the cable in the connector preventing it from accidentally pulling out. Crimping also forces copper pins in the connector to push down and make contact with the separate wires.

  8. You are now finished terminating one end of the cable. Repeat the process on the other end of the cable and when you are done, insert the cable into a cable tester and run a wire test to make sure that none of the wires are accidentally crossed, by not being in the right order, or open by not touching the connector pins. Depending on the cable tester you may need to read the manual to understand the device output.

  9. Lastly, test your cable by using it on your network. Attach the cable to your computer’s NIC and the other end to your switch. Do you see green lights? Open the Network Connections dialogue box in Windows, does it show a properly enabled and active connection on the NIC. You can also look for the status in your system tray network connections icon. If you have an internet connection, can you browse the web? If not can you ping your gateway from a command prompt?

Subnetting a Subnet with VLSM

VLSM Overview

Variable Length Subnet Masks (VLSM) are used to create subnetworks of varying sizes. This can be done as long as the IP address spaces of the subnets do not overlap. VLSM gives network designers the ability to not waste public IPv4 addresses by creating networks in sizes they need. Early dynamic routing protocols were not designed to work with VLSM because they were designed around classful IPv4 addressing. Modern routing protocols are designed to work with VLSM and classless inter-domain routing (CIDR). For the Cisco CCNA exam, you will need to know how to create subnets of varying sizes that do not have overlapping address spaces.

In the video tutorials below, I demonstrate how to solve a typical variable length subnet mask multiple choice question. The type of which you might see on an exam.

Video Tutorials – VLSM


Video Tutorials on Subnetting

The following ten video tutorials represent my most recent series on Cisco CCNA IPv4 subnetting. My personal feeling is that the only way to learn subnetting is to understand how it is working in binary. Subnetting makes sense if you try to understand it from the perspective of the binary number system. You can definitely tell how important I feel this topic is in order to do well, and pass your Cisco CCNA exam. Out of this series of videos, the last three seem to be the most popular. I hope these videos help your learning on the topic of subnetting.

In the videos I cover classful and non-classful network masks, the binary process of ANDing, class A, class B, and Class C subnetting, and typical IPv4 subnetting questions you may see on a multiple choice exam.

Application Layer

Application Layer Overview

The Application Layer is the layer closest to the end user. When you are using a program that is going to send something or contact someone over the internet you are using a network application that operates at the Application Layer. Each program/application that sends data over a network is identified by a particular protocol, at Layer 4 this protocol is associated with a port number. For example a web browser like Internet Explorer requests and receives pages from web servers its protocol is HTTP the hyper text transfer protocol and its correlative port number is port 80.

The applications that we use at Layer 7, the Application Layer are web browsers (HTTP) like Internet Explorer, a file transfer programs (FTP) like Filezilla, email clients (SMTP) like Microsoft Outlook Express and all flavors of Instant Messaging programs and P2P applications. There are also processes that run in the background that run at Layer 7, like DHCP which automates the process of requesting and receiving an IP address from a DHCP server. If you want to see these protocols in action all you need to do is use Wireshark. For instance, if we use the example of DHCP we learn that initiating DHCP involves a DHCP client talking to a DHCP server. The process is: 1. Client sends a DHCP DISCOVER 2. Server responds with a DHCP OFFER 3. Client sends a DHCP REQUEST 4. Server responds with a DHCP ACKnowledgement You can see the process of a client obtaining an IP address with DHCP in Wireshark (see video tutorial below).

This is a diagram of the OSI and TCP/IP Models and how they correspond to PDUs, Protocols and Devices 

This is a visual diagram of the process data goes through when sent over a network in a layered architecture


Video Tutorials – Wireshark, nslookup, Telnet

In this video I show the process of DHCP address acquisition by analyzing the PDUs using Wireshark

In this video, I use nslookup to resolve domain name servers to their ip addresses