Networking Core 1

What is FTP

1. Client-server protocol

2. Used to upload and download files

3. Insecure because it transmits in plain text

4. Ports: tcp20(Server)/tcp21(Client)

What is Telnet

1. Sends usernames and passwords in plain text

2. Ports: tcp23

3. Text-based command-line interface for remotely configuring devices like routers and switches

What is SSH

1. Used for shell/command-line access to remote systems

2. Port: tcp22

3. Encrypts transmitted data

4. Secure remote command-line connectivity for server administration and secure file transfer (via SFTP/SCP)

What is SMTP

1. Sending and relaying email messages using the store and forward model

2. Uses MAIL FROM: to specify sender and RCPT TO: to designate the recipient

3. Port tcp25 (tcp587 for SMTPS)

4. SMTPS uses TLS/SSL encryption

What is DNS

1. Translates human-readable domain names into IP addresses

2. use nslookup to verify DNS resolution

3. TCP/UDP port 53

Common DNS record types

1. A Record: Maps a hostname to an IPv4 address

2. AAAA Record: Maps a hostname to an IPv6 address

3. CNAME Record: Creates an alias for a hostname

4. MX Record: Specifies mail server

5. TXT Record: Stores arbitrary text commonly used for SPF, DKIM, and DMARC

6. PTR Record: Performs a reverse lookup

When do you check for DNS issues

When you can ping an IP address but can’t load websites

What is DHCP

1. Automatically assigns IP addresses, subnet masks, default gateways, and DNS information to clients

2. DORA (Discover, Offer, Request, Acknowledge)

3. Static manually assigned and Dynamic are randomly assigned

4. Port: udp67(Server), udp68(Client)

When do you need to troubleshoot DHCP

1. When the IP address is in the 169.254.x.x range (APIPA assignment)

2. Use ipconfig /release and ipconfig /renew to reset a client’s network settings

What is HTTP and HTTPS

1. Ports: tcp80(HTTP), tcp443(HTTPS)

2. Transmits web traffic

3. HTTP isn’t secure while HTTPS encrypts data with TLS/SSL encryption

What is POP3

1. Port: tcp110

2. Protocol for receiving emails

3. Deletes messages from the server after delivering them to the client

4. Used for devices with limited storage

What is IMAP

1. Ports: tcp143(insecure), tcp993(secure)

2. Receives emails like POP3, but doesn’t delete them from the server

3. Used for synchronization

What is NetBIOS

1. Port 137 (UDP/TCP) NetBIOS Name Service (NBNS): Name registration and resolution

2. Port 138 (UDP): NetBIOS Datagram Service for connectionless communication and broadcast messages

3. Port 139 (TCP): NetBIOS Session Service for establishing Connection-orriented sessions for file and printer sharing

4. Port 445 (TCP/UDP): Direct hosting of SMB over TCP/IP, used by Windows 2000 and later to bypass NetBIOS

5. Called NetBT when transferred over TCP/IP

6. Use nbtstat to troubleshoot

What is LDAP

1. Port tcp389

2. Used for authentication

3. Sends data in clear text

4. LDAPS encrypts over port tcp636

What is SMB also known as CIFS

1. Allows clients to read/write files and request services from servers on a network

2. Ports: tcp445, tcp/udp 137,138, and 139 (look to NetBIOS for uses)

3. v1 is insecure, v2/3 offer better performance and security

4. Cross platform with Linux

What is RDP

1. Port tcp3389

2. Provides a full graphical desktop session

3. Only used by windows Pro and up

4. Not secure by default but can be protected with VPNs, NLA, or jump boxes

RDP vs. Quick Assist

RDP for unattended administrative access or when the user does not need to see the session; Quick assist or Remote Assistance for Attended support where the user must approve and watch the technician

RDP vs. VNC

RDP for Windows-to-Windows connections; VNC(port 5900+) for cross-platform remote control

RDP vs. SSH

RDP for graphical desktop access; SSH for secure command-line administration, mainly Linux or network devices

RDP vs. VPN

VPN to gain network access to internal resources (like file shares); RDP to control the desktop interface of a specific machine

What is TCP

1. Connection oriented and reliable protocol

2. Establishes a connection before sending data

3. Tracks packets

4. Ensures correct arrival sequence

5. Retransmits lost data

6. integrity>speed

What is UDP

1. Connectionless and unreliable

2. Sends data without establishing a connection

3. Faster than TCP

4. Speed>accuracy

Characteristics of the 2.4 GHz Band

1. Longer range and better penetration

2. Lower speeds

3. High congestion

4. Only 3 non-overlapping channels (1,6, and 11) in North America

5. Supports 802.11b, 802.11g, 802.11n and Wi-Fi 6 (802.11ax)

6. Required for Legacy devices and IoT sensors

Characteristics of the 5 GHz Band

1. Higher speeds and less congestion

2. Shorter range and poor penetration

3. Larger number of non-overlapping channels allowing for better channel planning and wider bandwidths

4. Supports 802.11a, 802.11n, and Wi-Fi 5 (802.11ac)

5. Ideal for laptops, smartphones, and high-bandwidth activities

Characteristics of the 6 GHz Band

1. High speeds and less congestion but shorter range and poor penetration

2. Low number of overlapping channels

3. Only supports 802.11ax

What devices cause interference over the 2.4 GHz band

1. Microwaves

2. Cordless phones

3. Baby monitors

4. Bluetooth devices

Characteristics of 802.11a

Frequency band: 5 GHz

Max theoretical speed: 54 Mbps

Key Characteristics: Deprecated; early 5 GHz standard

Characteristics of 802.11b

Frequency band: 2.4 GHz

Max theoretical speed: 11 Mbps

Key Characteristics: First widely adopted; susceptible to interference

Characteristics of 802.11g

Frequency band: 2.4 GHz

Max theoretical speed: 54 Mbps

Key Characteristics: Backward compatible with b; uses OFDM

Characteristics of 802.11n

Frequency band: 2.4 and 5 GHz

Max theoretical speed: 600 Mbps

Key Characteristics: Introduces MIMO; Uses 20/40 MHz channels

Characteristics of 802.11ac

Frequency band: 5 GHz

Max theoretical speed: 7 Gbps

Key Characteristics: Wi-Fi 5; uses wider channels (80/160 MHz) and MU-MIMO

Characteristics of 802.11ax

Frequency band: 2.4 and 5 GHz

Max theoretical speed: 14 Gbps

Key Characteristics: Wi-Fi 6; Improved efficiency and latency for dense environments

What is WPA2

1. Baseline when WPA3 is unavailable and is more secure than outdated WEP

2. Uses AES-CCMP encryption

3. Uses 802.11X/EAP

4. Uses PSK

5. Vulnerable to offline dictionary attacks if passphrase is weak

What is WPA3

1. Preferred modern choice

2. Enhanced security by using SAE instead of PSK to resist offline dictionary attacks

3. Uses 802.11X/EAP

4. Uses AES-CCMP or GCMP encryption

What is NFC

1. Used for contactless payment, access control, bootstrapping, and Bluetooth pairing

2. Bidirectional data exchange

3. Does not require line of sight

4. Vulnerable to data interception (if unencrypted), man-in-the-middle attacks, denial of service (via frequency jamming), and the need for authentication to prevent unauthorized transactions or access if a device is lost

5. Hold closer if not working

What is RFID

1. Use radio frequencies to submit authentication information to access points

2. Unidirectional

3. Used for authentication and tracking

4. Some contactless payments and smart cards

5. Supply chain, logistics, and access control