Cisco Networking
What is a Network?
A network is the mechanism that enables distributed computers and users to communicate and share resources from data transmission.
OSI Model Layers
Application Layer
The Application Layer is the only layer that will interact with the user. It is the highest layer in the OSI Model. The Application Layer effectively moves data between your computer and the server.
Uses Protocols Like: HTTP (Hypertext Transfer Protocol) and DNS (Domain Name Service)
Presentation Layer
The Presentation Layer is responsible for encrypting, compressing, and format the data so it is readable for the Application and Session Layer to use.
Session Layer
The Session Layer defines how the data is formatted between the devices either side of the link. What it does is it creates a stable connection between 2 devices.
Transport Layer
The Transport Layer is responsible for transporting frames from one device to another device. It uses protocols like TCP (Transport Control Protcol) and UDP (User Datagram Protocol)
What is the difference between TCP and UDP?
- TCP ensures data delivery and sends a return package making it more reliable.
- UDP also ensures data delivery but doesn't send that return package so it isn't that reliable.
Network Layer
The Network Layer routes data from one location to another, or across to a different network. Layer 3 devices like routers are able to route data from different networks to find the destination using custom made ip addresses made from the ARP (Address Resolution Protocol)
Data Link Layer
The Data Link Layer is adjacent to the Physical Layer. And uses a numeric identifiers such as Media Access Control (MAC) address. Layer 2 devices such as switches, or multi-port bridge, uses the MAC Address to make decisions.
Physical Layer
The Physical Layer is the lowest layer on the OSI model and transmits binary data to the Data Link Layer.
Types of Ip Address
IPv4
Internet Protocol Version 4 was the first ip address that was created and is written in 4 octets of decimal numbers. So a common example is: 192.168.1.0. There are only 3.4 billion available addresses so when the internet began to grow the developers had to fix the issue
Private Ip Address
The Private Ip address is a different type of IP address where it contains it own network range the only issue is that the address isn't able to access the internet. So the developers added the NAT (Network Address Translation) which is located in your default router which translates your ip address to a public ip address.
IPv6
When the internet became to grow out of control the developers had no choice but to introduce a new type of the ip address. IPv6 or Internet Protocol version 6 which uses 8 groups of 4 hexadecimal numbers divided by colons. Ex: 2001:0db8:0000:0000:0000:8a2e:0370:7334
Subnet Mask/Subnetting
Subnet Mask
A subnet mask is a number that defines a range of ip addresses available within a network. The Subnet mask just shows how many host can be part of that network. Ex: 255.255.255.0 meaning it can have 253 host in that subnet since .1 and .255 are taken up by the broadcast address and the network address.
How does Subnetting Works?
Subnetting works when you change host or network bits to network or host bits. So when you only need lets say 51 host you will subnet the address so you only need 64 host so the new address would be 192.168.1.171 if the original address is 192.168.1.2 since when you do the logical And gate 192.168.1 will stay the same since the first 3 octets are 255.255.255
CIDR Notation
CIDR Notation was invented to identify what the subnet mask is easily so for example /1 is 128.0.0.0 and /24 is 255.255.255.0.
Switching
How Switches Function?
When the Physical Layer transmits data to the Data Link Layer. The switch looks at the MAC address to make the decision.
Basic Switch Modes
Once you connect your switch you are able to set some configurations. Once you first enter the switch you will be in EXEC Mode. Once you enable the switch by typing in enable you will enter Privilege EXEC Mode. Typing in conf t will enter you in Global Configuration Mode.
Switch Commands
Here are some commands you can try out to configure your switch.
- enable -- enters you in Privilege EXEC Mode
- conf t -- enters you in Global Configuration Mode.
- hostname -- changes the hostname of the device
- interface (interface type) -- enters you into the interface configuration mode
- line console (console num) -- enters you into line configuration mode
- enable pass passwd -- creates a password
- enable secret passwd -- creates a secret passwd
- show -- shows everything
- banner motd "msg" -- displays a banner
- interface vlan -- enters to vlan configuration