• Shorts for Redundant Array of Independent Disk
• It is the fail-safe mechanism to handle failure of hard disk.

RAID 0

• No redundancy.
• If one hard drive fails, then we lose info

source

RAID1

• One redundancy.
• It is fault tolerant.

RAID 5

• Requires at least 3 hard drives.
• Parity data is saved, so 1 hard drive failure is fine.

• Parity data is created by the XOR operator.
  • 1010 XOR 1010 –> 0000

source

RAID6

• Requires at least 4 hard drives.
• Can handle 2 disk failures.

RAID10

• Combination of RAID1 and RAID0.

RAID setup hands-on

• People type Domain name to access to the server, but IP address is what computer needs when they request/send data.

• Therefore, DNS should be converted into IP address. It is not too simple, because computers cannot have tons of DNS-IP matching info in their memory. They request DNS server to get IP info.

• For example, google.com , There is invisible . at the end of ‘com’, so it is google.com.

  • . is root domain and it is usually hidden

  • DNS is needed to be interpret backwards.

    • . => com => google
    • It has a tree structure.

    

How is it propagated around internet?

• Domain name has a tree structure.

  • From the top, Root => Top-level DN => Second level DN => SubDN

    생활코딩 WEB-2 Domain Name System

    

• Types of DNS Server

  1. DNS recursive resolver : It is served by ISP(Internet Service Provider)
  2. Root name server
  3. Top Level Domain/ TLD name server
  4. Authoritative name server

  

  생활코딩 WEB-2 Domain Name System

YT Source : TechTerms - DNS explained

• ex) When we type ‘google.com’,

  ​ => It is automatically converted into ‘google.com.’ , Dot at the end!

  ​ => It goes to ‘.’ Root server. It has IP info of ‘com, net, org…’.

  ​ https://root-servers.org/

  • If it is google.com. then in this step, It will return the IP of .com TLD Name server.

  • And then , TLD IP address returns to the computer, and computer again sends request to look for google.

  • This process repeats until It hits Authoritative name server(?) and return the IP address.

DNS records

How to add DNS entries to a DNS server?

https://docs.microsoft.com/en-us/windows-server/networking/technologies/ipam/add-a-dns-resource-record

ipconfig /displydns
ipconfig /flashdns

Host file location

C:\Windows\System32\drivers\etc\hosts

• In the past, People override their hosts file with Standford Research Institute.
• Stanford Research Institute has all the match info of Domain Name and IP
  • New records were manually added by people.
  • It took too long to update all.
  • People had to update their hosts file constantly to gain new info.
  • during operation time..

DNS principles

• As soon as the computer is connected to lan/wifi, It sets the domain name system server automatically by DHCP.

• When you type address, then It will look up hosts file first (Cache is also written here!) if there is no matching info found, then It will send traffic to DNS server.

  

  Control Panel > Network and Internet > Network Connection > Wi-Fi or Ethernet > Properties > IPv4

nslookup yejip.com
nslookup -type=a yejip.com
the same

DNS Zone

https://www.youtube.com/watch?v=f7bmOXCpkrg

IPv4, IPv6,CIDR notation,Subnet, DHCP, APIPA

IPv4

• Internet Protocol Version 4 (IPv4) Addressing

  ex) 172.248.8.5
  

• Dotted-decimal notation
• 32-bits in length
  • IPv4 consists of 4 octets(0~255).
  • Each octet is divided by dot.

IPv4 traits

subnet mask, CIDR notation, Class a, Class b, Class c , public IP, private IP ,special IP

• Subnet mask

  • It defines network portion(1) and host portion(0).
  • ‘1’ is filled from the left side in order.

  

• CIDR notation

  • It is a compact representation of an IP address and subnet mask.
  • CIDR stands for Classless Inter-Domain Routing.
  • It represents the number of ‘1’s in binary notation.

• Class A, B, and C

  • IPv4 is divided into two part. Network and Host. Big companies like Microsoft owns Class A IP. From my understanding, They would have lots of resources to serve people, meaning that hosts who hold info should be a lot.

  

  

• Public IP

  • Routable
  • It must be purchased before use through your Internet Service Provider (ISP).
  • 

• Private IP

• Non-routable
• Network Address Translation (NAT) will enable computers with private IP connect to the internet by matching private IPs to one public IP.

• special IP
  • Loop back address
    • 127.x.x.x range
    • ex)127.0.0.1
  • Automatic Private IP Addresses (APIPA)
    • static IP address and cannot reach a DHCP server
    • Range of 169.254.x.x
    • If you get IP range of this, it means that your DHCP is not working. (Not possible to connect to internet)

Data flow - IPv4

• Unicast : single sender, one recipient

  

• Multicast : single sender, multiple recipients

  

• Broadcast : single sender, recipients

Assigning IP Address

• Type
  • Static
  • Dynamic
• Components of IP Address
  • IP Address
  • Subnet Mask
  • Default Gateway
  • Server addresses
    • DNS or WINS

• DHCP

  • Dynamic Host Control Protocol (DHCP)

  • Provides clients with IP, Subnet mask, Default gateway, DNS server, WINS server, Other variables needed for VoIP

    

• APIPA
  • Automatic Private IP Address (APIPA)
  • Devices with no static IP, and no DHCP access
  • Allows a network device to self-assign an IP address from the 169.254.0.0/16 network
  • Non-routable

subnetting

• Borrowing bits from the host portion and adding them to the network portion. It enables original pool of network to be separated, which is secure and better use of IP Address.

• More efficient use of IP addresses than classful default.

  

• classful subnet

  • Default, Only one network

• classless subnet

  • More than 1 network. Total number of available IPs decreases as the first and last IP in each subnet are for Network ID and Broadcast respectively.
  • Borrow host’s section in subnet mask.

• The way to calculate the number of subnets and IPs according to CIDR

IPv6

• IPv4 is running out, due to lots of devices using WIFI.
• Enough IPv6 addresses for every person on the planet (5 x 10^28)
• IPv6 does not need DHCP to assign its IP. It uses auto configuration to discover the current network and selects its own host ID based on its MAC using the EUI64 process

Address type

• Globally routable unicast addresses s
  • Begins with 2000 to 3999
• Link-local address
• Begins with FE80
• Multicast addresses
• Begins with FF

Data flow

• Unicast and Multicast are similar to IPv4.

• Anycast

  • one to the nearest ones

    

• 4-layer model of network.
• Compared to OSI model, TCP/IP is more relevant to actual world network system.

Layer1) Network Interface

• It represents physical and electrical characteristics.
• ex) Ethernet, Token Ring, FDDI, RS-232

Layer2) Internet

• Packages data into IP datagrams
• Route IP datagrams across networks
• ex) IP, ICMP, ARP, RARP

Layer3) Transport

• This layer provides communication session management between hosts.
• ex) TCP, UDP

Layer4) Application

• It Defines protocols.
• ex) HTTP, TELNET, FTP, SNMP, DNS, SMTP, SSL, TLS…

How to transfer data over networks?

• Ports

  • It can be 0 to 65,535
  • It is divided into ‘Reserved Ports’ and ‘Ephemeral Ports’
    • Reserved : 0 to 1023
    • Ephemeral : 1025 to 65,535 short-lived transport port.

• Data Transfer

  • It contains the destination IP address and port information.

    

• IPv4 Packets

  • Source/Destination Address
  • IP Flags
  • Protocol (TCP? UDP?)

What are some famous Ports and Protocols?

You can check the ports

netstat -ano | find ":Required port number"

• Windows Server Update Services (WSUS) is an update service that allows administrators to centrally manage the distribution of patches and security updates.

• It provides latest Microsoft product updates

• In WSUS/Updates/All updates section, there are catalogs of Update info. You can choose what to update and then approve.

  

• Computers can belong to small group. ==> Each group can have different update I think.

  

Source - ms docs

Source - nedimmehic.org

How it is installed?

The information in this section is from Youtube channel ‘InfoSec Pat’

Overall Process

1. Configure IP ADdress and rename the server and join server to the domain
2. Install WSUS Role from the Server Manager.
3. Configure WSUS and GPO for the Servers.
4. Verify WSUS installation

1. Configure IP Address and rename the server and join server to the domain

• WSUS Computer: Configure IP Address. This computer is not yet used as a WSUS. We are making this computer as a WSUS now!

  

• ADDS/DNS/DHCP Computer: Add new computer which just joined our domain to ‘Servers’ group.

• There is also a WSUS-Servers OU, and CORE computer is in. However, It is not dealt well in the video. I need to figure it out what the heck is this….

?

2. Install WSUS Role from the Server Manager.

• WSUS Computer: From server manager, click ‘Add Roles and Features’ and add ‘WSUS’ role.

• Select storage (where the contents for the updates are gonna be sitting)

  

3. Configure WSUS and GPO for the Servers.

• ADDS/DNS/DHCP Computer:

  • Add new group policy ‘WSUS’

  

• ADDS/DNS/DHCP Computer:

  • Computer Configuration => Policies => Administrative Template => Window Components => Windows Update

  • 3 main settings

    • 1. Configure Automatic Updates
    • 1. Specify intranet Microsoft update service location

      ​ -specify intra Microsoft update service (DNS server ip ) (port number is important)

    

    • 1. Automatic Updates detection frequency

• Attach new role to WSUS-Servers OU.

4. Verify WSUS installation

https://community.spiceworks.com/how_to/169570-how-to-install-and-configure-wsus-on-windows-server-2019

What complaints people have for it?

Source : https://study.com/academy/lesson/windows-server-update-services-wsus-definition-uses-setup.html

• It is only supported on Windows Server (Expensive licensing required).
• It requires at least 4GB of memory to run (the more updates, the more RAM needed).
• It requires hundreds of GB to store downloaded updates. Additional selected products and update types increase this amount.
• The management database can occasionally be corrupted through normal usage, thus crashing the server and requiring cleanup and repair work to fix

What commands do to try and fix clients?

https://docs.microsoft.com/en-us/troubleshoot/mem/configmgr/troubleshoot-issues-with-wsus-client-agents

How to approve/disapprove updates?

http://woshub.com/wsus-update-approvals/

https://www.youtube.com/watch?v=OgiuKJyIp_g

How to control what products are offered?

https://documentation.solarwinds.com/en/success_center/patchman/content/spmag_selectmsproductsandclassifications.htm

—Unrelated—

Security

• what you know - Password
  • based on word is good to remember and pretty secure. so like “mouse-orange-desktop” .
• who you are - biometrics
  • Fingerprint, your eyes
• what you have - MFA (Multi Factor Authenticator)

Exchange Admin Center

• Mailboxes : Mails in box.

• Groups : When you want to send an email to certain group of people, It can be done by this feature.
• Resources : It keeps track of schedule for resource usage, so It is not double booked.
• Contacts : ?

https://docs.microsoft.com/en-us/exchange/exchange-admin-center

https://docs.microsoft.com/en-us/exchange/architecture/client-access/exchange-admin-center?view=exchserver-2019

Active Directory

How to check win-up for computers

• go to WSUS server, and Tools-WSUS(The last one) and check

subnet, broadcasting domain, Arp cache

Router : routs traffic

Arp cache : map an IP address to a given MAC address

from the official docs,

• To add a domain user or group
  1. In the Users / Groups window, click Add.
  2. In the Enter User or Group names dialog box, select domain users or groups by doing one of the following:
     • In the Enter User or Group names field, type a user or group that exists in the domain or as a local user or group on the computer. Then click Check Names to resolve it to the full existent name.
     • Click Find to open the standard Select Users or Groups dialog box. Then select domain users or groups.
  3. Click OK. The domain users or groups are added.

source - ms docs

• from HO and reference - How to add users to active directory

1. In Active Directory Users and Computers, right click and click new.
2. add a user. done

Reference Page

Domain Controllers vs Active Directory

How to join PCs to a domain

How to join PCs to a domain

• Window Server

  • Windows Server is the platform for building an infrastructure of connected applications, networks, and web services, from the workgroup to the data center. source - ms docs

  • Don’t get confused by the one we are using at home.

    

• What is domain?

  • Domain is a network that enables all users on the same network to use any computer on the network.

• Then, How to join PCs to a domain?

  1. On the Start screen, type Control Panel, and then press ENTER.

  2. Navigate to System and Security, and then click System.

     

  3. Under Computer name, domain, and workgroup settings, click Change settings.

     

  4. On the Computer Name tab, click Change.

  5. Under Member of, click Domain, type the name of the domain that you wish this computer to join, and then click OK.

     

     • The ID and PWD are registered on the domain. so you can join the domain!(?)

     

  6. Click OK, and then restart the computer

• My personal computer does not belong to any domain, because it is not added to any active directory domain but my work computer does. I made a screen shot of other post. source - groovypost.com

  source - ms docs

How to create an email address using Exchange (2019)

This post has good info!

source : Youtube Video

What is WSUS?

• Windows Server Update Services
• It provides latest Microsoft product updates

source - ms docs

1. Unboxing!

• My supervisor, kindly enough, put all the sets of components inside the case.

• These are the components!
  • The case
  • Motherboard
  • CPU (intel i5 core)
  • SSD M.2 1000 GB
  • RAM
  • Graphic card
  • Power supply
  • +ifixit kit

2. Wear anti-static strap on and start!

• Wear anti-static strap and connect the other side of it to the PC case. metal part. (This picture is only an example of how to wear and use.)

• Put motherboard on the desk. Now you are ready to build a computer!

3. CPU and Cooler fan

• put CPU into a motherboard. match the orientation.

  

• and put fan on the CPU.

  • The heat compounds will be placed on the CPU to convey heats from CPU to Metal blades.
  • Metal is highly conductive, so metal blades are useful strategy to remove heat from the CPU.

• Make sure to have enough space between fan and wire, or the fan will hit the wire and makes noise!

  

• Connect the wire to the motherboard.

  

4. Install SSD into motherboard

• Remove M.2 shield to install SSD

• Install binding post corresponding to the size of M.2 SSD

• Put M.2 shield back and it’s done.

5. Put I/O shield to the case, and install motherboard

• Don’t forget to putu I/O shield before you install your motherboard to the case, or you need to do it over.
• Match the orientation by I/O shield and I/O panel on the motherboard.2

• like this!

6. Connect fan, I/O cables to the motherboard

• Connect CPU fan and PC cover fan to the motherboard.

• Put cables behind the cover for space management and connect to the motherboard.

7. Install graphic card to the motherboard

• Install the graphic care do PCI express slot.

8. Install power supply, and connect to the mother board

• Cable management is a must!

• Thankfully, we are NVME SSD. so few cables are used.

D O N E!!