CCNA
Week 1 (Networks. Basic configuration)
Cisco Foundations - Configuring a Cisco Device - Programs and Console Connections
Starts talking about console cables, the name of the entry that you plug into the console cable is
RJ-45. He recommends the site monoprice to buy cheap cables.
Connecting to the cisco switch
1. Get a console cable
2. Plug the serial end into the back of your pc
3. Plug the RJ-45 end into console port in switch
After those steps you need to open a terminal program, some examples of programs that can be
used in that case are:
- Putty (free)
- Tera term (free)
- SecureCRTfsiOO but the best)
- Minicom (free) (linux and apple)
Inside the program the recommend configurations are:
The serial line usually is C0M1, other than some situations with USB to serial adaptors, that can be
seen in the computer manager menu in ports.
Speed is 9600, Data bits 8, Stop bits 1 and Paty and Flow control are none.
2. Working with the Cisco IOS
The Internetwork Operating System (IOS) is a command-line method of configuring a Cisco device, it
is a software that is consistent through nearly all Cisco devices. Have the advantage of "learn it
once" and use it many times and is more powerful than any graphic interface.
Understanding IOS Command modes
Switch> - User mode
Switch# - Privileged mode
Switch(config)# - Global configuration mode

151* Mow nmutioMow romnam now
Knowing the modes of your Cisco device is more important than knowing what commands to type.
User mode have limited options
Privileged mode have access to see all the information but can't change anything
Globa configuration is where you can change? configure everything, but all the changes are globally
affected.
When you want to change the configuration of a specific part you have to move to a specific
interface or line
All most used Commands are described in the end.
You can use a shortcut of ary command as long as it has enough characters to be the only one
starting with those letters. Like enable can be used as "en1.
3. Base Configuration
Performing an initial configuration
Hostname "name" - To give a hostname to device
Negating commands - just put the word "no" before a command to remove the command used, ex:
’ no hostname", would remove the hostname that was inserted before.
Passwords
There are 3 different passwords to be enable in the device:
Console password: Set a password to access any mode. To enable a console password, you
need to move to Global conf and from there go to "line console 0 1 that is the line for the
console. After being inside the line you can just type "password WORD" to define a
password and after type "login" to enable it. otherwise will not be enabled. Because even if
the password is set, if no login is required so won't be needed to use the password.
Telnet/SSH password: The purpose of setting a telnet/SSH password, is about the security to
configure the switch from distance without letting other people access the same. To

configure a telnet password, it is needed to move to the line vty, the difference between the
line console to the line vty is that the line console there is only 1 port, the port 0. and the
line vty depends on the cisco device but have an average of 16 lines, that can be configured
individually together.
So. the command line is line "vty STARTING line ENDING line if you just want to configure
line 0. would be 'line vty 0 D", but if you want to configure line 0-15 would be "line vty 0 15".
And after being inside those lines you can set the password with "password W0RD" r in the
line vty you don't need to use the login command.
Enable password: This is to set a password if someone wants to move to privileged mode.
Since this is just one for the hole device, you don’t need to move to any lines, this can be
done in the global conf mode. There are 2 ways of setting a enable password, with the
command enable password and with enable secret, the difference between then is that
when show running conf, the enable password will show the password in plain text and the
secret will be encrypted. So always prefer to use enable secret.
VTY = Virtual Terminal
Banner
Banner motd +WORD+
Saving configuration
There are two ways of saving your changes and configurations, the first one is with "run" that saves
in the RAM, if the switch needs to be power down, all the savings in that 'will be lost. The second way
is through "start ' that saves in the nvram (non-volatile ram} that everything is saved even if you
power down the switch.
The command to save is copy running config startup config, another command that is shorter and
can be used in 99% of cisco devices is write memory, that can be just "wr".
4.Con figuring SSH. User Accounts, and Password Encryption
Configuring SSH on a Cisco device
1. Configure your hostname
2- Configure a domain name, using the command "ip domain name WORD"
Generate encryption keys, using the command "crypto key generate rsa" and then select the
number of bits that will be used to generate the key
4- Enable SSH v2, using the command "ip ssh version 2"
Create a username with the command "username WORD secret WORD"
6- Choose to allow telnet and 55H. using the command '’transport input telnet ssh"
2- Enable local login, go to "line vty 0 15" again and use the command "login local’1 so the
system can use the username detail to log in the 55H, otherwise will not work because the
system is programmed to only use the password without a username.

Week 2 (OSI t Binary)
l,Speaking Binary
Reviewing Ip Basics
There are 3 different classes of subnet masks:
A -255.0.0.0
B - 255.255.0.0
C - 255.255.255.0
When the ip address is combined with the subnet mask, defines the network and host parts.
The network part is where are the 255 and the hosts the 0s.
The biggest network that you want to create is with 500 hosts.
Operates in layer 3(Network layer)
To calculate what the number is in binary, first you need to write a table as below:
128 64 32 16 8 4 2 1
Starting from the left until the right, seen if the number above fits in the number that you want to
put in binary, if is bigger, put 0 and go to the next, if it is smaller the put 1, decrease the amount
from the original value and go on until the original number comes to 0.
Ex: 12
0 0 0 0 1 1 0 0
220
1 1 0 0 1 0 0 0
With 8 bits you can convert a number until 255.
2.Cisco Foundations - Network Components, Diagrams, Cables, and Speed
Just information about how the network works.
3. Cisco Foundations - Speaking the Language of the OSI Model
The OSI model is a standardized architecture defining network communication.
The nugget is all about the understanding of the 051 model, if you have any doubts about the layers,
go back to this nugget and write everything about it Follow the OSI model with some examples
below:

L a y e r # Layer Name Protocol Protocol
Data Unit
1
Addressing
5 Application HTTP, SMTP, etc,.. Messages n/a
4 Transport TCPflJDP Segments/
Datagrams PcrtWs
3 Network or
Internet IP Packets IP Address
2 Data Link Ethernet, WiFi Frames MAC Address
1L 1 Physical 10 Base T 802.11 Bits n/a
4. Cisco Foundations - Basic IP Addressing - Filling in the Gaps
Assigning IP address
Static - You put the address manually and the IP address will not change, since you have to put all of
them manually and keeps difficult to keep track if there are many computers, most of companies use
DHCP (Dynamic Host Configuration Protocol)
DHCP - Automatically assigned IP address based in the range selected
DHCP Relay - Allow a router to send the DHCP broadcast to the DHCP server to get the IP address
assigned to it.
Multiple IP address -The same computer can be assigned with multiple IP addresses but only with
one primary, but it will answer to all the IP addresses assigned to it.
Public and private IP addresses
Private address are IP addresses that can only work internally in a LA.N/WAN.
Public address are the ones that you use to connect to the internet (ISP)
Automatic IP address is when the computer is configured to be assigned an IP address via DHCP but
when it can’t contact with the DHCP server, an automatic IP address is assigned to allow it to use in
LAN, it won't be possible to connect to the internet until the problem is solved.
Loopback addresses are for testing, but out of the 6 millions IP addresses reserved only one is used:
127.0.0.1.
Special addresses: The first and last IP addresses of the subnet are for the network and the
broadcast.
Private addreses:
10.0.0.0 through 10.255.255.255
172.16.0.0 though 172.31.255.255
192.168.0.0 though 192.168.255.255 MOST COMMON! USED
Automatic addresses:
169.254.0.0 though 169.254.255.255

Loopback addresses:
127.0.0.0 though 127.255.255.255
Special addresses:
Ex: subnet 172.30.100.0 mask 255.255.255.0
172.30.100.0 network and 172.30.100.255 broadcast
Classes of addresses
To determine the class of the IP address is only needed to look to the first octet of the IP address to
identify it class. The importance to identify the classes of the IP address if because each class have a
default subnet mask. This only apply to classful address.
Class A: 1-127 Default subnet mask 255.0.0.0 or 78
Class B: 128-191 Default subnet mask 255.255.0.0 or 716
Class C: 192-223 Default subnet mask 255.255.255.0 or 724
Not usable:
Class D: 224 - 239 (Multicast)
Class E: 240-254 (Experimental)
Classful addresses are the one who uses the default subnet mask
Classless address are the ones who uses one class address with another subnet mask.
Ex: Classful: 10.0.0.0 Default subnet mask 255.0.0.0 or 78
Classless: 10.0.0.0 using subnet mask 255.255.255.0 or 724
Types of communication
Unicast - One message to one device
Multicast - One message to a group of devices
Broadcast - One message to everybody
Week 3 (Subnetting, DHCP)
l.Creating Subnets Based on Network Requirements
Subnetting is a technique to divide a single network into multiple smaller networks, known as
subnetworks or subnets. The purpose of subnetting is to partition a large network into smaller, more
efficient subnets, which can improve network performance, security, and organization.
To do the subnetting, there are 3 steps:
1. Determine number of networks and convert to binary
2. Reserve bits in subnet mask and find your increment
3. Use in crement to find your n etwo rk ra nges

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Ex: A company bought the Class C address 216.21.5.0/24 and would like to use 5 networks. Since
this is only one network with 254 hosts available, it will be needed to do subnetting.
So going to the step:
1- 5 networks = 00000101 = 3 bits needed
0 0 0 0 0 1 0 1|
128 64 32 16 S 4 2 1
2- Subnet mask 255.255.255.0, in bits = 11111111.11111111.11111111.00000000
Network part is represented by the Is and the Host part by the Os.
So, if you want to increase the network part and to get 5 networks you need at least 3 bits, so you
want to increase the network part taking 3 bits of the host part:
11111111.11111111.11111111.11100000
After that, you already can convert back from binary to decimals to see the new subnet mask:
i! 1 1 0 0 0 0 0
12S 64 32 16 8 4 2 1
128+64+32 = 224
The new subnet mask is: 255.255.255.224 or /27
The increment is the lowest network bit converted back to a decimal number.
So, in this case the lowest network bit would be 11111111.11111111.11111111.11100000
And when converted to decimal looking above in the table is 32.
3- The last step is to use the increment (32) to find the network range.
So, just get the network and start increasing using the Increment:
216.21.5.0 - 31 216.21.5.160 - 191
216.21.5.32- 63 216.21.5.192 - 223
216.21.5.64 - 95 216.21.5.224 - 25 5
216.21.5.96- 127
216.21.5.128- 159
And each of those addresses are the starting position of each subnet. After you discover them, you
can just complete with address where each subnet ends, that is 1 number less than when the other
begins.
So. since you already have all the subnets you can assign each subnet where they needed, in this
case they only need 5 networks, so you could just use the first five subnets range.

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Always remembering that you can never use the first and the last address because they are for the
network and broadcast. So, in the first subnet 216.21.5.0 - 31, the ones that can be used are
216.21.5.1-30 and so on with all the others.
To know how many subnets were created is just use the formula 2A N, N being the number of bits
allocated, in this case were 3, so 23 = 8. And to the hosts the same thing but taking in consideration
the number of Os left and to reduce 2 of the total because always 2 of them are unusable, so in this
case 2*5-2= 30.
2. Creating Subnets Based on Host Requirements
The procress changes a little when it is based on Hosts Requirements, the base steps are the same
but when getting in the part to reserve the bits will change. So taking the same example of the
previous module but changing the requirement will be this way:
A company bought the Class C address 216.21.5.0 /24 and would like 30 hosts per network.
1 - 30 host = 5 bits
2- Subnet mask 255.255.255.0, in bits = 11111111.11111111.11111111.00000000
So you want to have at least 5 bits reserved for the hosts per network, you start from the right to the
left saving the 5 first Os, and since you already saved the hosts you wanted, the rest you can still
change to Is. to become network:
11111111.11111111.11111111.11100000
Transforming back to decimals would be: 255.255.255.224 or /27
And the increment would be 32.
3. Reverse Engineering Subnet Problems
It is probably the most common thing to do, when you have the IP address and the subnet mask and
need to discover the network ranges.
Ex: IP: 192.168.1.127
Mask: 255.255.255.224
Since you already have the subnet mask you can skip the first step and half of the second, and just
need to find the increment.
To find the increment is just pass the decimal number to binary and see the lowest bit.
11111111.11111111.111111111.11100000
128+64432 = 224
And the lowest one used is 32, so that's the increment.
So the network ranges are:
192.168.1.0-31
192.168.1.32 - 63

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192.168.1.64-95
192.168.1.96 - 127
192.168.1.128
So in that case the problem would be that the ip address is destined to be used as broadcast since is
the last ip address of the network.
GREAT EXCEPTION
To be safe always subtract 1 when finding networks.
And add 1 when finding hosts.
Because of the network and broadcast. And one of them are being saved because of the 0 being
accounted for.
4. Variable Length Subnet Masking (VLSM)
Variable Length Subnet Mask (VLSM) is a technique used in IP network design to create subnets with
different subnet masks. VLSM allows network administrators to allocate I P addresses more
efficiently and effectively, by using smaller subnet masks for subnets with fewer hosts and larger
subnet masks for subnets with more hosts.
Follow an example below:
4 «
When they ask for the most efficient addressing possible with different sizes of network, this means
that it is needed to use VLSM to make different sizes of subnet, using different subnet masks to each
network.
When doing VLSM you always want to start with the biggest network and going down until reach the
smallest.
Here is the solution to the example:

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W e e k 4 ( R o u t i n g protocols, Static Route)
l,How Applications Speak - TCP and UDP
TCP (Transmission control protocol) and UDP (User datagram protocol) are the primary transport
protocols used today. Being UDP the unreliable way to send data and TCP the reliable. But this
reliability has a cost, since to be reliable it must check if the information really got there, there is a
delay so this can happen, this is the reason some programs use UDP, because of the fast
transportation, like video chats, that the don't really matter if some package is lost in the
communication, the important thing is really the speed of the data is being transmitted to be
possible to be live.
DNS. or the Domain Name System, translates human readable domain names (for example.
www.amazon.com) to machine readable IP addresses (for example, 192.0.2.44).
Wireshark is a free and open-source packet analyzer. It is used for network troubleshooting, analysis,
software and communications protocol development
First thing when you open Wireshark, you want to go to List the available capture interfaces" to see the
available interfaces (if there are more than one) and what is the one who is actively having packets being
sent and received. After you selected the correct one, will open all the communication happening
The rest of the video were about demonstration and explanation of the way the communication is
showed in Wireshark.
2,Understanding Routing Core
Until now, everything was focused in the VLAN, working with switch, configuring them and working
in the internal network, but now will be explained the routing process.
Routing is the process of moving packets between IP- based networks. Routers are 105 powered, this
means that all the power the routers has comes from the possibility to be configured by a software,
different from the switch that usually has a faster hardware to process the information.

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CCNA Week 1 Networks Basic Configuration

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