Network+

PAN

• personal area network, kind of like headphones and a smart watch connecting to your device like a cellphone

Clients

• wifi enabled thermostatsand other smart devices that connect to a network to receive commands and share data.

Servers

provide resources to the rest of your network

Hub

• older network device that connects clients and servers, over a local area network (LAN)

Bridges and Switches

more update to date version of a HUB

Routers

Used to connect networks together and have the ability to forward traffic based on the IP.

Firewall

a device that blocks or allows traffic from external the network

they use ACL (access control lists) which are kind of like a block list at a club the bouncer uses

Intrusion Detection Systems

it monitors network activity, and detects unauthorized access to the network and lets the network admins know

Intrusion Prevention System

detects threats but also takes action to prevent them from accessing the network

Controllers

These control the flow of the network to network devices. They work as an “overhead” for multiple access points and multiple accounts, as in a computer that manages wireless communication, ensuring efficient data transfer and connectivity across devices in a network.

Network-attached storage devices

a hardware based file system for multiple clients to share data

Storage Area Network

provides access to block level storage , handles large volumes of data

Media

physical items used to transfer data from one client to another or to the server, like cables

Wide Area Network link

used to connect networks over a large geographical area

OSI Reference Model

the standard to show how devices interact with one another with by International Standards

OSI Application Layer

This is for end users where files are transported and hosted on an application, like outlook, establishes availability of partners

OSI Presentation layer

This layer is for preparing, encoding, and translating data for the Application layer, defines how two devices can encode, prepare and translate

OSI Session layer

This layer is for controlling how two different devices connect and for how long, manages, tracks and terminates connections

OSI Transport layer

the layer of transferring data with different protocols like TDP and UDP, and load balancing, checks to see whether TCP or UDP will be used

OSI Network layer

houses the layer with the IP address and dictates where things go

OSI Data Link layer

this is the layer that holds our switches and the ethernet MAC addresses

OSI Physical Layer

this is the HUB layer, the lowest layer and is responsible for transporting the rawest bits of data that are unstructured, items that are physical characteristics

TCP/IP protocol

this protocol is the main protocol used today in most environments, and is layered very similar to the OSI Model

TCP/IP protocol application

represents data users, encoding the data, and controls the dialog, these are the upper layers

TCP/IP transport application

represents the transfer of end devices across a diverse network

TCP/IP internet application

determines the load balancing, logical, and the best pathways in the network

TCP/IP link application

determines the hardware devices MAC and transport of raw data bits, similar to the data and physical layers of the OSI

How do you connect to a Switch that does not have an IP yet?

With a console cable DB9 to RJC45, RJ45 goes into the switch, while the serial cord goes into the PC, since they dont have serial ports anymore a USB dongle must be used

Flow Control

controls the messages being sent from the sender to the retreiver, if the sender has a faster connection and goes past, the receiver can send a message saying to slow down, hence flow control, this is within layer 4 (transport layer)

Session Multiplexing

Process where a host is able to support multiple sessions at the same time and manage the traffic streams over a single link.

How does the receiver differentiate what application certain traffic is for?

They can check where traffic goes based on the port number the traffic is FROM, example HTTP web traffic uses port 80, SMTP email uses port 25

What is included in the layer 4 header as well with the sender?

The header has a source port number, this helps when tracking sessions, both source and destination port are used to track this, think of it like mail return address and sending address

TCP (Transmission Control Protocol)

• connection oriented and data can be sent bilaterally

• it sequences segments so that no packets are lost

UDP (User Datagram Protocol)

• this protocol is not connection oriented

• while it is less reliable, it is more faster, since there is no overheard and “handshake”with no flow control

TCP vs UDP

TCP is usually picked for being more reliable. When overhead is too expensive UDP is selected. This is used more for video and audio.

Network layers main use.

Logically routing packets to their destination and for Quality of Service

Subnets

IP addressing that partitions the overall network into smaller versions.

Unicast Traffic

This traffic of packets just goes to one destination, a single destination host, when traffic copy gets sent to switch it goes to one destination

Broadcast Traffic

This traffic goes to all hosts on the subnet, when it gets to the switch it gets to all the devices on the subnet and connected with that switch.

Multicast Traffic

This traffic goes to multiple interested hosts, not just subnet.

Broadcast vs Multicast Traffic

Broadcast sends traffic to multiple receivers on the subnet whether they want it or not. Multicast sends traffic to multiple receivers, but it’s targeted.

Computers in Binary

-With these electrical impulses are on or off, so there’s

two choices 0 or 1, unlike 10 in decimals

• each column we have 2 possible choices 0 or 1

• when a column gets added its multiplied by 2

• starts from 256, 128, 64, 32,16, 8, 4, 2, 1

• if a number fits here its a 1 if not its a no, whatever the remainder is from the last “check”

• should always have 0 left over from a final check

How long is an IPV4 address and why?

It is 32 bits long, it has 4 “octests” inside and each of those is 8 bits long

What is needed for traffic to move across DIFFERENT subnets?

A router is needed for this kind of travel.

Subnet mask

Used for routing, when a subnet mask has 255.255.255.0 it means that 255 IP addresses can fit here.

This is like an IP address that identified the network and host parts within the original address, this helps specific routes for sending data to a destination.

Whats the highest number that can go in an octet?

The highest would be 255.

How do we know that a certain number in an IP address will be the same?

If the number of 255.255.255.0 is there, the 0 can be any number of 0-255, based on what device its assigned to. If it was 255.255.200.0 the third octet can be different.

Portions of an IP address

• Consider 192.168.1.204, the network portion is 192.168.1

• The host portion is 204.

• On a street the network portion of the IP address is 192.168.1.204 this would be seen as the physical street, the host portion would be seen as the address

Whats the point of a gateway/router?

This handles routing packets out of your network/subnet to another network.

What are two IPS you cant touch in a network?

The broadcast address(first) and last in your network, when traffic goes to them, they send it to all the other IPs in the network.

What are IP classes?

• Type A is 1.0.0.0-126.255.255.255 with a SN of 255.0.0.0, the first octect stays the same but the others can vary, 16,777,214 options

• Type B is 128.0.0.0 - 255.255.0.0 SN 255.255.0.0

• Type C is 192.0.0.0 0223.255.255.0 SN is 255.255.255.0

• Type D 224.0.0.0 - 239.255.255.255

• Type E 240.0.0.0 - 255.255.255.255

• class A is host heavy, and it has the most

• class C is where home networks reside

• D and E do not require subnets, theyre for multicasting, very important to networking, E is experimental

What is a classless network?

This is where youre taking a class and changing the subnet of it from its default.

What is loopback

An IP starting with 127, seen as network testing on your device, your PC virtually has all the IPs in the range of 127, so if you ping that and get a reply youre golden.

What are private IP addresses?

Addresses that are dedicated and not unique to others.

Network Address Translation

The router gives out private IPS to devices in your network that have the same IP as devices not on it. It takes a public IP from ISP first. And when traffic leaves the router it gets sent as a public IP.

First, the ISP gives the router a public IP. The router sets devices that went to send traffic out with this same IP, think of it as like a “filter”.

Subnet Mask

-These dictate what parts of the IP are network bits and host bits.

-255.255.255.0 shows that the last octet has 254 addresses

• if the network needs more host bits you can add a 0 to an octet

• host bit range is found by adding how many 0’s are in binary format

Breaking a network into multiple subnets?

-if we want to have 18 networks youd count how many youd need in the binary cheat sheet, youd go from the right

-128 64 (32) 16 8 4 2 1

-in this case youd have 5 bits

-youd start from the left 11111000

-add these up and youd get .248 in the last octet 255.255.255.248

Slash Notation

Notation where it shows the subnet mask represented in slash format

this is in regards to how many 1’s are found in the binary format

example 255.255.255.0 has 24 1’s in it, hence it can be 192.10.69.12/24

if the last octect is not 0’s and has 1’s theyd be counted if they show from the left and onward

Unicast

This is seen as cmmunication between one destination and one source. An example can be from your PC to a youtube server to watch a video.

Multicast

One to many connection. This is used in file sharing situations like a teams meeting. One PC sending files and traffic to another user on the same network. Class D works with this.

Unicast vs Multicast addresses

Unicast has its own source address, and on top of that, multicast has its own address used for that as well, example is 239.0.0.1

CIDR

Classless Inter-Domain Routing, the system built in 1993 allowed for address classes to be split or subnetted into smaller networks. This is basically like the official name for subnetting

How to find first and last host addresses

first find the network address and add 1 and with the broadcast address subtract 1(cause youre setting the last bit as 0

How to find how many subnets will be with a subnet mask

youd look at the last number you borrowed from in the bit translation like if you went out all the way to 6 borrowed, youd add that number as a power of 2 which would be 32

How to find how many hosts are in a subnet

You must see what class it belongs to if an IP is given.

Youd take how many bits were borrowed to make that amount like if /24 and they want a /28 subnet.

With the example above, we borrowed 4.

We would take the numbered borrowed and apply it to the power of 2 in this case it would be 16

Which routing protocol gives us the ability to Subnet by size?

Variable Length Subnet Masking

Best way to design subnets?

Find the largest segment of hosts and allocate a suitable size for it.

Youd allocate this subnet at the start of the address space.

RFC

(requests for comments) they specify private IP address ranges which are not routable on the public internet, more so the local internet and provide guidelines and standards for the internet's architecture and protocols.

Private IP address

IP addresses that are not meant to connect with the public internet

Ranges of private IP addresses

• 10.0.0.0 - 10.255.255.255

  • SN /8

• 172.16.0.0 - 172.31.255.255

  • SN /12

• 192.168.0.0 - 192.168.255.255

  • SN /16

IPv4 vs IPv6 in terms of IP range.

IPv4 addresses use a 32 bit format which has them run out of addresses much quicker. While on the other hand IPv6 uses 128 bits allowing a much larger allocation of available IP addresses

RFC 1918

This a private IP address range that is not routable on the public internet. These are private addresses on your local network. Kind of like the 10.0.0.0 range at MWH.

NAT’s role in migration of IPv4 to IPv6

NAT translates private IP addresses from their inside network to outside public IP addresses, which makes IPv4 and IPv6 “communicate” with each other

Why is IPV6 used more on phones.

IPV6 is used more with phones because it has newer technologies that allow for this format, and there are alot of phones.

What is a PDU?

pieces of data that are divided into different items depending on what headers are attached, all pieces of data are these but not vice versa

Names for PDU through the layers

While in the application layer it is Data, in transport the Segment, network it is a packet, and data-link layer a frame.

How many bits does the ethernet MAC address have and why?

This MAC address has 48 bits, first 24 are the OUI (organizationally unique identifier) which identfied the manufacturer of the ethernet port. THe last 24 bits is vendor assigned.

Power over Ethernet

A type of switch where if you plug something into it, it powers the device. This is how the cisco deskphones at work work.

Straight Through Cable

This cable has two pairs of transmit and receiving that are next to eaxh other connecting Media Dependent Interfaces to Media Dependent Interface crossovers(like a switch)

Cross Over Cable

This cable has the wires cross eachother, this is used for connection between like devices like switch to switch, PC to PC.

Copper Cable

This cable was the older format and made by twisted pairs of copper wires inside of it, a slam benefit is that is cheaper than fiber optic. Legacy infrastructure still use this.

Fiber Optic

This cable is run and transmits data via light. It is a premium and made for better speed and distance.

Half-duplex mode.

This is how hubs operate, attached hosts cant send and receive data at the same time but only one or the other.

Collision domain.

A section of a network where devices share the same transmission medium, where data packets can collide if multiple devices transmit at the same time. This comes into play with half-duplex mode, and Carrier-Sense Multiple Access (CSMA) is employed to help with this.

How is data moved through a HUB?

Hubs operate at layer 1 of the OSI model. When a frame is picked up it is flooded out all the ports apart from the one it was received on, and the hosts must process all packets.

How is data moved through a Switch?

The switch operates at layer 2, and when a frame is received with a KNOWN MAC address the switch will send the frame out only the relevant port. When the frame is received from a MAC that isnt learned yet, all the ports are flooded except the one it is received on.

How does a switch “learn” a new MAC address?

This when a frame is sent through the switch to another host connected to and the switch records the source MAC address and the port it was received on, allowing it to forward future frames to the correct port.

Router vs Switch

Routers work on a level 3 layer, while switches are 2. Routers have more compatibility with other functionality like serial.

How does a router help in a infrastructure with routing?

While switch transfer data within one subnet, a router can move data/frames between multiple subnets, hence being level 3 and not 2.

What is an advanced switch?

These switches are layer 3 aware and can route traffic between different IP subnets.

Domain Name System

this resolves website addresses to IP addresses. MOst enterprises have their internal DNS server that it resolves. For example, being able to connect to certain MWH websites while on their network. If it fails it would need to forward the request to public DNS.

DNS Client

Software or hardware that is needing the DNS query to be resolved, this sends queries to the DNS resolver.

DNS Resolver

This queries the DNS database and returns the corresponding IP address to the DNS client.

Address Resolution Protocol (ARP)

protocol that helps find a hardware address for a given IP address on a local network, when a request goes out to send a frame, it gets sent out via broadcast traffic and the right destination mac sends it back

How does traffic work with ARP between different networks?

When a device on one network needs to communicate with a device on another network, it uses ARP to find the MAC address of the gateway router that connects the two networks, facilitating the transmission of data.

Default Gateway

a device that forwards traffic depending on the destination IP address

Default Gateway Address

address of the router that sends data to networks outside of its own local network

DNS vs ARP

DNS resolves domain names to IP addresses for delivering purposes, while ARP maps IP addresses to MACs, ARP paves the road for travel and DNS helps finds addresses to go to

What changes and stays the same for a frame/packet?

It changes destination MAC addresses as it goes through traffic, but source and destination IP addresses stay the same.

Routing table.

The best available paths to a destination network on a router either learned dynamically or configured statically.