Cisco CCNA Certification

This article will be used to track the study progress on the Cisco CCNA certificate.

Must Add to the test Sheet

• Making a Subnet Calculator
• TCP/IP vs OSI Model

1) Introduction to Networks

1.1) Dissecting Communications

1.2) Network Communications Models

1.2.1) Categorizing Data Transmissions

1.2.2) The OSI Model

1.2.3) TCP/IP vs. OSI Model

1.3) Encapsulation

1.3.1) How Encapsulation works

Segment - chunk of data on the Transport Layer(4)

Packet - chunk of data on the Network Layer(3)

IP Header - From the minimum length of 20 to a total length of 60 bytes

Frame - a chunk of data with a Data Link layer header.

Ethernet Header - contains the MAC address. From the minimum length of 20 to a total length of 60 bytes

Ethernet II Frame - Header Explained

1.4) Data Networks and Addressing

1.4.1) Addressing the Network

Ethernet - uses MAC addresses to address frames.

The first six hexadecimal values are the manufacturer ID and the last six are the serial number of the network interface card.

1.4.2) How Local Communication Works

1.4.3) How Global Addressing Works

Global addressing uses IP addresses.

The tablet will create a frame and encapsulate the packet and send to the router default gateway.

The router will discard the frame analyses the packet and re-encapsulate to send to the internet(next-hop)/upstream gateway.

1.4.4) IP Networks

The subnet mask separates the IP in different networks.

2) Network Layer Addressing and Subnetting

2.1) Introduction to Binary

2.1.1) Binary 101

To count in binary we use place holders and exhaust the possible combinations of zeros and ones.

2.1.2) Converting Binary to Decimal

We just need to multiple the place holder value by itself and add the results.

The binary number above is 192 in decimal.

2.1.3) Converting Decimal to Binary

• First ask the question if it is possible to subtract the number from the place holder value and have left a positive number or 0.
• If yes rinse and repeat.
• Convert the YES to one and the result will be the binary number.

2.1.4) Hexadecimal

To count in hexadecimal we follow the table above.

2.2) Introduction to IP Addressing

2.2.1) What is an IP Address?

An IP address is a unique identifier.

It is composed of 4 octets and each octet contains 8 bits summing a total of 32 bits.

2.2.2) Classless Addressing

IPs are classless and use the network mask to subnet all the available ranges.

2.2.3) Classful Addressing

Classful addresses does not have subnet masks and are divided by classes.

2.2.4) Address Types

There are tree types of address.

Network Address - All bits in the host port are 1.

Broadcast Address: All bits in the host portion are 0.

Host Address: All addresses without zeros and ones in the host portion.

We need to break an address into binary to determine the type of the address.

2.2.5) Private and Public Addresses

2.3) Introduction to IP Subnetting

2.3.1) Framework for Discussing Subnetting

To do subnetting, we must convert the addresses to binary.

2.3.2) Making a Subnet Calculator

This calculator is used to correlate the number of bits in the network mask with the available number of networks and how many hosts each network can have.

2.3.3) Subnetting a Network

Let's subnet the network below into 8 smaller networks.

1) Lookup into the network calculator chart.

2) Set up the problem

3) Calculate Network 0

4) Convert the addresses to decimal.

5) Calculate Network 1

6) Repeat the steps 3 and 4 until the last network.

2.4) Introduction to IPv6

2.4.1) IPv6 Addresses

2.4.2) IPv6 Address Structure

We always keep IPv6 addresses networks at 64 bits long.

• We do not need to but it is highly recommended.

1) We can eliminate leading zeros to shorten an IPv6 Address.

• We can only have one double colon in an IPv6 address.

2.4.3) IPv6 Address Operation

IPv6 operates like IPv4 addresses.

• To use an IPv6 on the internet it has to be a Unicast IPv6 address.
• A different IPv6 address is needed for local communications.

2.4.4) IPv6 Address Types

2.4.5) How Many IPv6 Addresses?

Total of addresses : 340 undecillion, approximately 3.4×10³⁸

2.4.6) IPv6 Static Address

We can static configure IPv6 like IPv4 as seen on the example below.

2.4.7) IP Address Acquision - SLAAC

SLAAC stands for Stateless Address Auto-configuration.

• 1) The router advertises the network it is connected using its link local address.

• 2) The workstation chooses an IP address

Windows creates a random 64 bit identifier to the host.

Unix/Linux/MAC uses a system called Modified EUI - 64

• It is uses the workstation MAC Address and split in two and adds FF:FE
• Take the seventh bit and convert it to the opposite.

• 3) The host sends an Neighbor Advertisement message to the router with the new IPv6 Address

2.4.8) IP Address Acquision - DHCP

The DHCP server on the network can respond to IPv6 addresses requests.

It is recommended to use a DHCP server with IPv6 to allow for easier troubleshooting.

2.5) IPv6 Subnetting

2.5.1) The IPv6 Subnet Mask

IPv6 addresses normally are used in /64 networks which is the recommended.

2.5.2) Subnetting IPv6

Let's use an ISP as an subnetting example. The ISP has a /32 subnet and want to provision 5 customers with a /48 subnet.

2.5.3) Subnetting IPv6 /48

With the /48 the customer will now distribute the address within 5 physical locations in a way that each site can have 256 /64 networks.

• 1) Let's convert the 16 bits available for subnetting into binary, and move every 4 bits

Breaking the subnet every for bits allows easy subnetting, since it is only a matter of count in hexadecimal.

Keep counting in binary to determine the amount of /64 subnets each of the above subnets can accommodate.

The table above tells that each site needs a /56 subnet.

• 2) Counting the hexadecimal each network can be defined.

2.5.4) Subnetting IPv6 /56

London will subnet their /56 into the 5 office locations below.

There are 8 bits to work on the /56 subnet provided as seen on the pink highlighted area.

Keep counting and the subnets for each location should be like below.

2.6) Router Operation

2.6.1) Basic Router Operation

Let's examine a ping message going from host to server.

• 1) The ping message is encapsulated into an IP packet.

• 2) The packet is encapsulated into a L2 frame. With the source MAC Address of the host and destination the router gateway.

• 3) The router receives the frame, discards it.
• 4) Looks the IP destination in its routing table and finds it on the interface in the subnet 10.0.0.128/25.

• 5) It generates a new frame and forward it to the server.

• 6) The server then extract the packet, discard the frame and reads the payload in the packet. The payload contains the ping request and the server respond.

The response follows the same steps above.

2.7) Variable Lenght Subnet Masking

2.7.1) The Need for VLSM

13 Networks will be needed to accommodate the diagram above.

The ISP provides, a /21 subnet to be subdivided into smaller networks.

2.7.2) Setting up the VLSM Problem

The first step is to set up a list with the networks as seen below.

We need to use our Network Calculator to from step 2.3.2 to fill the table with the number of bits needed for each network as seen below.

2.7.3) Calculating Your Networks

Let's calculate the first subnet.

1) Add a divider on the 21 bits provided by the ISP.

2) Set the 9 bits on the host portion as defined on the step above. It gives the netmask of the subnet.

3) Calculate the Network address, First Usable Address, Broadcast Address and Last Usable Address in as seen on the table below.

Repeat the steps above incrementing the networks until the table is completed as below.

Let's calculate the networks for the example below.

The table below show the needed networks.

The result is the on the table below.

3) Ethernet Ops & Switch Config

3.1) Physical Layer Technologies

3.1.1) Twisted Pair Cabling

Twisted pair cable categories.

Cat6 cables have better insulation to prevent noise on the copper pairs.

Shielded cabling is used when running cables along devices that create EFM like fluorescent lights.

3.1.2) RJ-45 Connectors & Cable Types

The diagram below describes both wiring standards.

Crossover cables are used to devices of the same type.

Modern network cards automatically detects the type of cable.

Other types of cables.

3.1.3) Fibre Optics

Fibre optics types.

3.1.4) Wireless Ethernet(802.11)

The electrical magnetic spectrum is divided into channels. A range of frequencies used to transmit information.

3.2) Data Link Layer Technologies

3.2.1) Ethernet

Ethernet is one of the most used protocols used in networking today. It is one of the Layer 2 protocols responsible to move frames/packets around the network.

IEEE 802.3, also known as the Ethernet standard, is a set of standards and protocols defined by the Institute of Electrical and Electronics Engineers (IEEE) that specify the physical and media access control (MAC) aspects of the data link layer for wired Ethernet networks.

IEEE 802.3 has evolved over time to support various types of media, including twisted pair cables (10BASE-T, 100BASE-TX, etc.), coaxial cables (10BASE-2), and fiber optic cables (10BASE-F), enabling Ethernet to adapt to different network environments and requirements

3.2.2) Wireless

The wireless Ethernet protocols are also controlled by IEEE and has evolved over the years as seen on the table below.

3.2.3) Other Data Link Layer Protocols

3.2.4) Serial Communication Protocols

3.3) Introduction to Ethernet

3.3.1) A Brief History of Ethernet

3.3.2) CSMA/CD

This is a bus network and collisions are a voltage spike on the wire.

3.3.3) Duplex and Speed

3.3.4) Ethernet II Frame

A frame encapsulates a Layer 3 packet.

Each has its own max number of bits allowed.

The destination MAC address consists of several pieces. Manufactures have an ID provided by the IEEE when they purchase an Ethernet license. This ID are the first 24 bits and the other 24 bits is an unique number.