Section 2: Networking Flashcards
(125 cards)
1
Q
2.1 - Ports and Protocols - Introduction to IP
Series of moving vans
A
- Efficiently move large amounts of data: Use a shipping truck
- The network topology is the road: Ethernet, DSL, cable system
- The truck is the Internet Protocol (IP): We’ve designed the roads for this truck
- The boxes hold your data: Boxes of TCP and UDP
- Inside the boxes are more things: Applicaton Information
2
Q
2.1 - Ports and Protocols - Introduction to IP
TCP and UDP
A
- Transported inside of IP: Encapsulated by the IP protocol
- Two ways to move data from place to place: Different features for different applications
- OSI Layer 4: The transport layer
- Multiplexing: Use many different applications at the same time. TCP and UDP.
3
Q
2.1 - Ports and Protocols - Introduction to IP
TCP - Transmission Control Protocol
A
- Connection-oriented: A formal connection setup and close
- “Reliable” Delivery: Recovery from errors. Can manage out-of-order messages or retransmissions
- Flow control: The receiver can manage how much data is sent.
4
Q
2.1 - Ports and Protocols - Introduction to IP
UDP - User Datagram Protocol
A
- Connectionless: No formal open or close to the connection
- “Unreliable” delivery: No error recovery. No reodering of data transmissions.
- No flow control: Sender determines the amount of data transmitted. One-way communication
5
Q
2.1 - Ports and Protocols - Introduction to IP
Why would you ever use UDP?
A
- Real-time communication: There’s no way to stop and resend the data. Time doesn’t stop for your network.
- Connectionless protocolas: DHCP (Dynamic Host Configuration Protocol) and TFTP (Trivial File Transfer Protocol)
- The data might not get through: The application keeps track and decided what to do. It might do anything.
- UDP is fast.
6
Q
2.1 - Ports and Protocols - Introduction to IP
Communication using TCP
A
- Connection-oriented protocols prefer a “return receipt”: HTTPS (Hypertext Transfer Protocol Secure) and SSH (Secure Shell).
- The application doesn’t worry about out of order frames or missing data. TCP handles all of the communication overhead. The application has one job.
7
Q
2.1 - Ports and Protocols - Introduction to IP
Speedy delivery
A
- The IP delivery truck delivers from one (IP) address to another (IP) address: Every house has an address, every computer has an IP address.
- Boxes arrive at the house / IP address: Where do the boxes go? Each box has a room name.
- Port is written on the outside of the box: Drop the box into the right room.
- Port 80: web server unencrypted data (HTTP)
- Port 443: web server encrypted data (HTTPS)
- Port 25: mail server
- Port 123: time server.
8
Q
2.1 - Ports and Protocols - Introduction to IP
Lots of ports
A
- IPv4 sockets: Server IP address, protocol, server application port number. Client IP address, protocol, client port number.
- Non-ephemeral ports: Permanent port numbers. Ports 0 through 1023. Usually on a server or service.
- Ephemeral ports: Temporary ports. Ports 1024 through 65,535. Determined in real-time by the client.
9
Q
2.1 - Ports and Protocols - Introduction to IP
Port Numbers
A
- TCP and UDP ports can be any numer between 0 through 65,535.
- Most servers (services) use non-ephemeral port numbers. This isn’t always the case. It’s just a number.
- Port numbers are for communication, not security.
- Service port numbers need to be well known.
- TCP port numbers aren’t same as UDP port numbers. TCP 80 is not the same as UDP 80.
10
Q
2.1 - Ports and Protocols - Introduction to IP
Ports on the network
A
Web server - TCP/80
VoIP server - UDP/5004
Email server - TCP/143
11
Q
2.1 - Ports and Protocols - Common Network Ports
Port Numbers
A
- Well-known port number: Client and server need to match
- Important for firewall rules: Port-based security
- A bit of rote memorization: Becomes second nature after a while.
- Make sure you know port number, protocol and how the protocol is used .
12
Q
2.1 - Ports and Protocols - Common Network Ports
FTP - File Transfer Protocol
A
- tcp/20 (active mode data), tcp/21(control): Transfers files between systems.
- Authenticates with a username and password. Some systems use a generic/anonymous login
- Full-featured functionality: List, add, delete, etc.
13
Q
2.1 - Ports and Protocols - Common Network Ports
SSH - Secure Shell
A
- Encrypted communication link - tcp/22
- Looks and acts the same as Telnet.
14
Q
2.1 - Ports and Protocols - Common Network Ports
Telnet
A
- Telnet -Telecommunication Network: tcp/23
- Loging to devices remotely: console access
- In-the-clear communication (unencrypted): Not the best choice for production systems.
15
Q
2.1 - Ports and Protocols - Common Network Ports
SMTP: Simple Mail Transfer Protocol
A
- SMTP (Simple Mail Transfer Protocol): Server to server email transfer. tcp/25
- Also used to send email from a device to a mail server. Commonly configured on mobile devices and email.
- Other protocols are used for clients to receive email. - IMAP, POP3
16
Q
2.1 - Ports and Protocols - Common Network Ports
DNS - Domain Name System
A
- Converts names to IP addresses - udp/53: www.professormesser.com = 162.159.246.164
- These are very crictical resources. Usually multiple DNS servers are in production.
17
Q
2.1 - Ports and Protocols - Common Network Ports
DHCP - Dynamic Host Configuration Protocol
A
- Automated configuration of IP address, subnet mask and other options: udp/67, udp/68. Requires a DHCP server. Server, appliance, integrated into a SOHO router etc.
- Dynamic / pooled: IP addresses are assigned in real-time from a pool. Each system is given a lease and must renew at set intervals.
- DHCP reservation: Addresses are assigned by MAC address in the DHCP server. Manage address from onle location.
18
Q
2.1 - Ports and Protocols - Common Network Ports
HTTP and HTTPS
A
- Hypertext Transfer Protocol: Communication in the browser. And by other applications.
- In the clear or encrypted: Suppoted by nealy all web servers and clients.
- HTTP: tcp/80. Hypertext Transfer Protocol. Web server communication.
- HTTPS: tcp/443 Hypetext Transfer Protocol Secure. Web server communication with encryption.
19
Q
2.1 - Ports and Protocols - Common Network Ports
POP3 / IMAP
A
- Receive emails from server: Authenticate and transfer.
- POP3 - Post Office Protocol version 3. tcp/110. Basic mail transfer functionality. Receive message for one email.
- IMAP4 - Internet Message Access Protocess v4. tcp/143. Includes management of email inbox from multiple clients.
20
Q
2.1 - Ports and Protocols - Common Network Ports
SMB - Server Message Block
A
- Protocol used by Microsoft Windows: File sharing, printer sharing. Also called CIFS (Common Internet File System)
- Using NetBIOS over TCP/IP (Network Basic Input/Output System): udp/137 - NetBIO name services (nbname). udp/139 - NETBIO session service (nbsession)
- Direct over tcp/445 (NetBIOS-less): Direct SMB communication over TCP without NetBIOS transport.
21
Q
2.1 - Ports and Protocols - Common Network Ports
SMNP - Simple Network Management Protocol
A
- Gather statistics from network devices: Queries - udp/161. Traps - udp/162
- v1 - The original: Structured tables. In-the-clear.
- v2 - A good step ahead: Data type enhancements. Bulk transfers. Still in-the-clear.
- v3 - A secure standard: Message integrity. Authentication. Encryption.
22
Q
2.1 - Ports and Protocols - Common Network Ports
LDAP
A
- LDAP (Lightweight Directory Access Protocol): tcp/389
- Store and retrieve information in a network directory. Commonlu used in Microsoft Active Directory.
23
Q
2.1 - Ports and Protocols - Common Network Ports
RDP - Remote Desktop Protocol
A
- Share a desktop from a remote location over tcp/3389
- Remote Desktop Services on many Windows versions
- Can connect to an entire desktop or just an application
- Clients for Windows, macOS, Linux, Unix, iPhone, Android, and others.
24
Q
2.2 Network Devices
Network devices
A
- Many different devices and components: All have different roles.
- Some of these functions are combined together: Wirelss router/switch/firewall
- Compare different devices: Understand when they should be used
25
# 2.2 Network Devices
Router
* Routes traffic between IP subnets: Makes forward decisions based on IP address. Routers inside of switches sometimes called "layer 3 switches"
* Often connects diverse network types: LAN, WAN, copper, fiber
26
# 2.2 Network Devices
Switches
* Bridging done in hardware: Application-specific integrated circuit (ASIC). Forwards traffic based on data link (MAC) address
* Many ports and features: The core of an enterprise network. May provide power over ethernet (PoE)
* Multilayer switch: Includes routing functionality. Known as layer 3 switch.
27
# 2.2 Network Devices
Unmanaged devices
* Very few configuration options: Plug and play
* Fixed configuration: No VLANs
* Very little integration with other devices: No management protocols.
* Low price point: Simple is less expensive.
28
# 2.2 Network Devices
Managed switches
* VLAN support: Interconnect with other switch via 802.1Q
* Traffic prioritization: Voice traffic gets a higher priority
* Redundancy support: Spanning Tree Protocol (STP)
* Port Mirroring: Capture packets.
* External management: Simple Network Management Protocol (SNMP)
29
# 2.2 Network Devices
Access point
* Not a wireless router: A wireless router is a router and an access point in a single device.
* Asn access point is a bridge: Extends the wired network onto the wired network. Makes forwarding decisions based on MAC address.
30
# 2.2 Network Devices
Patch panels
* Combination of punch-down blocks and RJ-45 connectors
* Runs from desks are made once: Permanently punched down to patch pane.
* Patch panel to switch can be easily changed. No special tools. Use existing cables.
31
# 2.2 Network Devices
Firewalls
* Filters traffic by port number: OSI layer 4 (TCP/UDP). Some firewalls can filter based on the application.
* Can encrypt traffic into/out of the network: Protects your traffic between sites.
* Can proxy traffic: A common security technique.
* Most firewalls can be layer 3 devices (routers)
* Usually sits on the ingress/egress of the network.
32
# 2.2 Network Devices
Power over Ethernet (PoE)
* Power provided on an Ethernet cable: One wire for both network and electricity. Phones, cameras, wireless access points. Useful in difficult-to-power areas.
* Power provided at the switch: Built-in power - Endspans. In-line power injector - midspans.
33
# 2.2 Network Devices
PoE switch
* Power over Ethernet: Commonly marked on the switch or interfaces.
34
# 2.2 Network Devices
PoE, PoE+, PoE++
* PoE: IEEE 802.3af-2003: The original PoE specification. Now part of the 802.3 standard. 15.4 watts DC power., 350 mA max current.
* PoE+: IEEE 802.3at-2009: Now part of the 802.3 standard. 25.5 DC power, 600 mA max current.
* PoE++: IEEE 802.3bt-2018. 51 W (Type 3), 600 mA max current. 71.3 (type 4) , 960 mA max current. PoE with 10GBASE-T
35
# 2.2 Network Devices
Hub
* "Multi-port repeater": Traffic going in one port is repeated to every other port.
* Everything is half-duplex
* Becomes less efficient as network traffic increases.
* 10 megabit / 100 megabit
* Difficult to find today
36
# 2.2 Network Devices
Cable modem
* Broadband: Transmission across multiple frequencies. Different traffic types.
* Data on the "cable" network: DOCSIS (Data Over Cable Service Interface Specification)
* High-speed networking: Speeds up to 1Gigabit/s are available.
* Multiple service: Data, voice, video
37
# 2.2 Network Devices
DSL modem
* ADSL (Asymmetric Digital Subscriber Line): Use telephone lines
* Download speed is faster than the upload speed (asymmetric): 10,000 foot limitation from the central office (CO). 52 Mbit/s downstream / 16 Mbit/s upstream are common. Faster speeds may be possible if closer to the CO.
38
# 2.2 Network Devices
ONT
* Optical network terminal: Fiber to the premises
* Connect the ISP fiber network to the copper network: Demarcation poit (demarc) in the data center. Terminal box on the side of the building.
* Line of responsibility: one side of the box is the ISP. The other side of the box is your networl.
39
# 2.2 Network Devices
Network Interface Card (NIC)
* The fundamental network device: Every device on the network has a NIC. Computers, servers, printers, routers, switches, phones, tablets, cameras, etc.
* Specific to the network type: Ethernet, WAN, wireless etc.
* Often built-in to the motherboard: Or added as an expansion card.
* Many option: singel port, multi-port, copper, fiber.
40
# 2.2 Sofware Defined Networking
SDN (Softwar Defined Networking)
* Networking devices have different functional planes of operation: Data, control, and management planes.
* Split the functions into separate logical units: Extend the functionality and management of a single device . Perfectly built for the cloud.
* Infrastructure layer / Data plane: Process the network frames and packets. Forwarding, trunking, encrypting, NAT.
* Control layer / Control plane: Manages the actions of the data plane. Routing tables, session tables, NAT tables. Dynamic routing protocol updates.
* Application layer/ Management plane: Configure and manage the device. SSH, browser, API.
41
# 2.2 Network Devices
SDN data flows
* Between Application layer/ Management Plane: SSH, SNMP, API
* Between Control layer / Control plane: Dynamic routing protocols
* Between Infrastructure layer / Data plane: Network traffic.
42
# 2.3 Wireless Network Standards
Wireless Network Standards
* Wireless networking (802.11): Managed by the IEEE LAN/MAN Standard Committee (IEE 802)
* Many updates over time: Check with IEEE for the latest.
* The Wi-Fi trademark: Wi-Fi Alliance handles interoperability testing
43
# 2.3 Wireless Network Standards
802.11a
* One of the original 802.11 wireless standards. October 1999
* Operates in the 5 Ghz range. Or other frequencies with special licensing.
* 54 megabits per second.(Mbit/s)
* Smaller range than 802.11b. Higher frequency is absorbed by objects in the way.
* Not commonly seen today.
44
# 2.3 Wireless Network Standards
802.11b
* Also an original 82.11 standard. October 1999.
* Operates in the 2.4 GHz range
* 11 megabits per second (Mbit/s)
* Better range than 802.11a. Less absorption problems.
* More frequent conflict: Baby monitors, cordless phones, microwaves, ovens, bluetooth
* Not commonly seen today.
45
# 2.3 Wireless Network Standards
802.11g
* An "upgrade" to 802.11b. June 2003
* Operaties in the 2.4 GHz range
* 54 megabits per second (Mbit/s). Similar to 802.11a
* Backwards-compatible with 802.11b.
* Same 2.4 GHz frequency conflict problems 802.11b.
46
# 2.3 Wireless Network Standards
802.11n (Wi-Fi 4)
* The update to 802.11g, 802.11b, and 802.11a. October 2009
* Operates at 5 GHz and/or 2.4 GHz. 40 MHz channel widths.
* 600 megabits per second (Mbit/s): 40 MHz mode and 4 antennas.
* 802.11n uses MIMO: Multiple input multiple-output. Multiple transmit and receive antennas.
47
# 2.3 Wireless Network Standards
802.11ac (Wi-Fi 5)
* Approved in January 2014. Significant improvements over 802.11n
* Operates in the 5 GHz band. Less crowded, more frequencies (up to 160 MHz channel bandwidth)
* Increaed channel bonding: Larger bandwith usage.
* Denser signaling modulaation: Faster data transfers.
* Eight MU-MIMO downlink streams: Twice as many streams as 802.11n. 6.9 gigabits per second
* Maximum theortetical throughput per stream is 867 Mbit/s
48
# 2.3 Wireless Network Standards
802.11ax (Wi-Fi 6)
* Approved in 2021. The successor to 802.11ac/Wi-Fi 5
* Operates at 5 GHz and / or 2.4 GHz: 20, 40, 80, and 160 MHz widths.
* 1,201 megabits per second per channel: A relatively small increase in throughput. Eight bi-directional MU-MIMO stream.
* Orthogonal frequency-division multiple access (OFDMA): Works similar to cellular communication. Improves high--density installations.
* Maximum theoretical throughput of 9.6 Gbit/s
49
# 2.3 Wireless Network Standards
Long-range fixed wireless
* Wireless access point in a house with the stock antennas. You might get a range of 40 to 50 meters.
* Try connecting two buildings located miles from each other: Fixed directional antennas and increased signal strength.
* Outdoors: Minimal signal absorption or bounce.
* Directional antennas: Focused, point-to-point connection.
* Wireless regulations are complex. Refer to your country's regulatory agency.
* Frequency use: Unlicensed 2.4 GHz or 5 GHz frequencies. Addtional frequencies may be availanle. Additional licensing may be requiree.
* Signal strength: Indoor and outdoor power is usually regulated.
* Outdoor antenna installation is not trivial. Get an expert. Be safe.
50
# 2.3 Wireless Network Standards
RFID (Radio-frequency identification)
* It's everywhere: Access badges, inventory/ assembly line tracking, pet/animal identification, anything that needs to be tracked.
* Radar technology: Radio energy transmitted to the tag. RF powers the tag, ID is transmitted back. Bidirectional communication. Some tag formats can be active/powered.
51
# 2.3 Wireless Network Standards
NFC (Near Field Communication)
* Two-way wireless communication. Builds on RFID, which is mostly one-way
* Payment systems: Major credit cards. Online wallets.
* Bootstrap for other wireless: NFC helps with Bluetooth pairing.
* Access token, identity "card": Short range with encryption support.
52
# 2.3 - Wireless Network Technologies
802.11 technologies
* Frequency: 2.4 GHz or 5 GHs and sometimes both.
* Channels: Groups of frequencies, numbered by the IEEE. Non-overlapping channels would be ideal .
* Regulations: Most countries have regulations to manage frequency use. Spectrum use power output, interference requirements, etc.
53
# 2.3 - Wireless Network Technologies
Band selection and bandwidth
* 2.4 GHz spectrum for 802.11 - North America: Channels 1, 6 and 11
* 5 GHz spectrum for 802.11 - North America. Has more channels and bandwidth.
54
# 2.3 - Wireless Network Technologies
Bluetooth
* Remove the wires: Headsets, speakers, keyboards/ mice
* Uses the 2.4 GHz range. Unlicensed ISM (Industrial, Scientific and Medical ) band. Same as 802.11
* Short-range: Most consumer devices operate to about 10 meters. Industrial Bluetooth devices can communicated over 100 meters.
55
# 2.4 - Network Services
DNS server
* Domain Name System: Converts names to IP addresses. And vice versa
* Distributed naming system: The load is balanced across many different servers
* Usually managed by the ISP or enterprise IT departement. A critical resource.
56
# 2.4 - Network Services
DHCP server
* Dynamic Host Configuration Protocol: Automatic IP address configuration
* Very common service. Available on most home routers.
* Usually running on central servers.
57
# 2.4 - Network Services
File server
* Central storage of documents, spreadsheets, video, pictures, and any other files. A fileshare
* Standard system of file management: SMB (Server Message Block) for Windows, Apple filiing protocol (AFP) for Apple.
* The front-end hides the protocol: Copy, delete, rename, etc.
58
# 2.4 - Network Services
Printer server
* Connect a printer to the network: Provide printing services for all network devices.
* May be software in a computer: Computer is connected to the printer.
* May be built-in to the printer: Newtork adapter and software.
* Uses standard printing protocols. SMB (Server Message Block), IPP (Internet Printing Protocol), LPD (Line Printer Daemon).
59
# 2.4 - Network Services
Mail server
* Store your incoming mail. Send your outgoing mail.
* Usually managed by the ISP or the enterprise IT departement. A complex set of requirements.
* Usually one of the most important service. 24/7 support
60
# 2.4 - Network Services
Syslog
* Standard for message logging: Diverse systems, consolidated log
* Usually a central logging server. Integrated into the SIEM
* You're going to need a lot of disk space. No more. More than that.
61
# 2.4 - Network Services
Web server
* Respond to browser requests: Using standard web browsing protocols - HTTP/HTTPS. Pages are built with HTMLS and HTML5
* Web pages are stored on the server: Downloaded to the browser. Static pages or built dynamically in real-time.
62
# 2.4 - Network Services
Authentication server
* Login authentication to resources: Centralized management
* Almost always an enterprise service. Not required on a home network.
* Usually a set of redundanct servers. Always available. Exteremely important service.
63
# 2.4 - Network Services
Spam
* Unsolicited messages: email, forums, etc.
* Various content: commercial advertising, non-commercial proselytizing, p hishing attempts.
* Significant technology issue: Security concerns, resource utilization, storage costs, managing th spam.
64
# 2.4 - Network Services
Spam gateways
* Unsolicited email: Stop it at the the gateway before it reached the user.
* On-site or cloud-based.
65
# 2.4 - Network Services
All-in-one security appliance
* Next-generation firewall, Unified Threat Management (UTM)/ Web Security gateway
* URL filter / content inspection
* Malware inspection
* Spam filter
* CSU/DSU
* Router, Switch
* Firewall
* IDS/IPS
* Bandwidth shaper
* VPN endpoint.
66
# 2.4 - Network Services
Load balancers
* Distribute the load: Multiple servers. Invisible to the end-user.
* Large-scale implementations: Web server farms, database farms.
* Fault tolerance: Server outage have no effect. Very fast convergence.
67
# 2.4 - Network Services
Load balancer features
* Configurable load: Manage across servers.
* TCP Offload: Protocol overhead
* SSL offload: Encryption/ Decryption
* Caching: Fast response.
* Prioritization: QoS
* Content switching: Application-centric balancing.
68
# 2.4 - Network Services
Proxy server
* An intermediat server: Client makes the request to the proxy. The proxy performs the actual request. The proxy provide results back to the client.
* Useful features: Access control, caching, URL filtering, content scanning.
69
# 2.4 - Network Services
SCADA / ICS
* Supervisory Control and Data Acquisition System: Large-scale, multip-site industrial control system (ICS)
* PC manages equipment: Power generation, refining, manufactuting equipment, facilities, industrial, energy, logistics.
* Distributed control system: Real-time informtion, system control
* Requires extensive segmentation: No access from the outside.
70
# 2.4 - Network Services
Legacy and embedded systems
* Legacy systems: Another expression for "really old". May also be "really important". Learning old things can be just as important as learning the new things.
* Embedded systems: Purpose-built device. Not usual to have direct access to the operating system
* Alarm system, door security, time card system.
71
# 2.4 - Network Services
IoT (Internet of Things) devices
* Appliances: Refrigerators
* Smart devices: Smart speakers respond to voice commands.
* Air control: thermostats, temperature control
* Access: Smart doorbells.
* May require a segmented network: Limit any security breaches.
72
# 2.5 - Network Configurations - IPv4 and IPv6
IP addressing
* IPv4 is the primary protocol for everything we do. Included in almost all configurations.
* IPv6 is now part of all major operating systems. The backbone of our internet infrastructure.
73
# 2.5 - Network Configurations - IPv4 and IPv6
IPv4 addresses
* Internet Protocol version 4: OSI Layer 3 address. Since one byte is 8 bits, the maximum decimal value for each byte is 255.
* 8 bits = 1 byte = 1 octect.
* 32 bits = 4 bytes.
74
# 2.5 - Network Configurations - IPv4 and IPv6
IPv6 adresses
* Internet Protocol v6 - 128-bit address. 340 undecillion.
* Your DNS is very important!
* First 64 bits is generally the network prefix (/64)
* Last 64 bits is the host network address.
75
# 2.5 - Network Configurations - IPv4 and IPv6
Networking with IPv4
* IP Address, e.g., 192.168.1.165. Every device needs a unique IP address
* Subnet mask, e.g., 255. 255. 255.0: Used by the local device to determine what subnet it's on. The subnet mask isn't (usually) transmitted across the network. You'll ask for the subnet mask all the time. What's the subnet mask of this network?
* Default gateway, e.g. 192.168.1.1: The router that allows you to communicate outside of your local subnet. The default gateway must be an IP address on the local subnet.
76
# 2.5 - Network Configurations - IPv4 and IPv6
DNS servers
* We remember name: professormessor.com, google.com, youtube. com
* Internet routers don't know names. Router only know IP addresses.
* Something has to translate between names and IP addresses. Domain Name Service.
* You configure two DNS servers in your IP configuration. That's how important it is.
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# 2.5 - Network Configurations - IPv4 and IPv6
Assigning IP Addresses
* IPv4 address configuration used to be manual: IP address, subnet mask, gateway, DNS servers, NTP servers, etc.
* October 1993 - The bootstrap protocol.
* BOOTP didn't automatically define everything. Some manual configuations were still required. BOOTP also didn't know when an IP address might be available again.
* Dynamic Host Configuration Protocol (DHCP): Initially released in 1997, updated through the years. Provides automatic address / IP configuration for almost all devices.
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# 2.5 - Network Configurations - IPv4 and IPv6
DHCP process
* DORA: A four-step process
* Discover: Find a DHCP server
* Offer: Get an offer
* Request: Lock in the offer
* Acknowledge: DHCP server confirmation
79
# 2.5 - Network Configurations - IPv4 and IPv6
Turning dynamic into static
* DHCP assigns an IP address from the first available from a large pool of addresses. Your IP addres will occasionally change.
* You may not want your IP address to change. Server, printer, or personal preference.
* Disable DHCP on the device: Configure the IP address information manually. Require additional administration.
* Better: Configure an IP reservation on the DHCP server. Associate a specific MAC address with an IP address.
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# 2.5 - Network Configurations - IPv4 and IPv6
Avoid manual configurations
* No DHCP server reservations. You configure the IP address manually.
* Difficult to change later. You must visit the device again.
* A DHCP reservation is preferable. Change IP address from the DHCP server.
81
# 2.5 - Network Configurations - IPv4 and IPv6
Automatic Private IP Addressing (APIPA)
* Also called a linked-local address. No forward by routers.
* IETF has reserved 169.254.0.0 through 169.254.255.255: First and last 256 addresses are reserved. Functional block of 169.254.1.0 through 169.254.254.255
* Automatically assigned: Uses ARP to confirm the address isn't currently in use.
82
# 2.6 - DNS Configuration
Domain Name System
* Translates human readable names into computer-readable IP addresses. You only need to remember www.Professormesser. com
* Heirarchical. Follow the path
* Distributed database: Many DNS servers. 13 root server clusters (Over 1000 actual server). Hundreds of generic top-level domains (gTLDs) -.com, .org, .net, etc.
* Over 275 country code top-level domains (ccTLDs) -.us, .ca, .uk, etc.
* TLD is top-level-domain
83
# 2.6 - DNS Configuration
DNS Lookup Commands
* dig
* nslookup
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# 2.6 - DNS Configuration
DNS records
* Resource Records (RR): The database records of domain name services.
* Over 30 record types: IP adddresses, certificates, host alias names, etc.
* These are important and critical configurations. Make sure to check your settings, backup, and test!.
85
# 2.6 - DNS Configuration
Address records (A) (AAAA)
* Defines the IP address of a host. This is the most popular query
* A records are for IPv4 addresses: Modify the A record to change the host name to IP address resolution.
* AAAA records are for IPv6 addresses. The same DNS server, different records.
86
# 2.6 - DNS Configuration
Mail exchanger record (MX)
* Determines the host name for the mail server. This isn't an IP address. It's a name.
87
# 2.6 - DNS Configuration
Text record (TXT)
* Human-readable text information: Useful public information. Was originally designed for informal information.
* Can be used for verification purposes: If you have access to the DNS, then you must be the administrator of the domain name.
* Commonly used for email securtiy. External email servers validate information from your DNS.
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# 2.6 - DNS Configuration
Viewing TXT records with dig
dig professormesser.com txt
89
# 2.6 - DNS Configuration
Viewing TXT records with nslookup
nslookup -type=txt professormesser.com
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# 2.6 - DNS Configuration
Sender Policy Framework (SPF)
* SPF protocol: A list of all servers authorized to send emails for this domain. Prevent mail spoofing. Mail servers perform a check to see if incoming mail really did come from an authorized host.
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# 2.6 - DNS Configuration
Domain Key Identified Mail (DKIM)
* Digitally sign a domain's outgoing mail: Validated by mail servers, not usually seen by the end user. The public key is in the DKIM TXT record.
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# 2.6 - DNS Configuration
DMARC
* Domain-based message authentication, reporting, and conference (DMARC): Prevent unauthorized email use (spoofing). An extension of SPF and DKIM
* You decide what external email servers should do with email that don't validate throught SPF and DKIM. That policy is written into a DMARC TXT record. Accept all, send to spam, or reject the email. Compliance reports can be sent to the email administrator.
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# 2.6 - Network Connections - DHCP Configuration
Scope Properties
* IP address range. And excluded addresses
* Subnet mask
* Lease durations
* Other scope options: DNS server, Default gateway, VOIP servers
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# 2.6 - Network Connections - DHCP Configuration
DHCP pools
* Grouping of IP addresses: Each subnet has its own scope. 192.128.1.0/24, 192.128.2.0/24,192.128.3.0/24
* A scope is generally a single contiguous pool of IP addresses. DHCP exceptions can be made inside of the scope.
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# 2.6 - Network Connections - DHCP Configuration
DHCP address assignment
* Dynamic assignment: DHCP server has a big pool of addresses to give out. Addresses are reclaimed after a lease period.
* Automatic assignment: Similar to dynamic allocation. DHCP server keeps a list of past assignments. You'll always get the same IP address.
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# 2.6 - Network Connections - DHCP Configuration
DHCP address allocation
* Address reservation. Administratively configured.
* Table of MAC (Media access control) addresses: Each MAC address has a matching IP address.
* Other names: Static DHCP assignment, static DHCP, static assignment, IP reservation.
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# 2.6 - Network Connections - DHCP Configuration
DHCP Leases
* Leasing your address: It's only temporary. But it can seem permanent.
* Allocation: Assigned a lease time by the DHCP server. Administratively configured.
* Reallocation: Reboot your computer. Confirm the lease.
* Workstation can also manually release the IP address. Moving to another subnet.
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# 2.6 - Network Connections - DHCP Configuration
DHCP renewal
* T1 timer: Check in with the lending DHCP server to renew the IP address. 50% of the lease time (default).
* T2 timer: If the original DHCP server is down, try rebinding with any DHCP server. 87.5% of lease time.
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# 2.6 - Network Connections - VLANs and VPNs
LANs
* Local Area Networks: A group of devices in the same broadcast domain.
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# 2.6 - Network Connections - DHCP Configuration
Virtual LANs
* Virtual Local Area Networks: A group of devices in the same broadcast domain. Separated logically instead of physically. SIngle switch instead of multiple.
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# 2.6 - Network Connections - DHCP Configuration
Configuring VLANs
* Local Area Networks: A group of devices in the same broadcast domain.
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# 2.6 - Network Connections - DHCP Configuration
VPN
* Virtual Private Networks: Encrypted (private) data tranversing a public network
* Concentrator: Encryption/decryption access devide. Often integrated into a firewall.
* Many deployment options: Specialized cryptographic hardware. Software-based options available.
* Used with client software: Sometimes built into the OS.
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# 2.6 - Network Connections - DHCP Configuration
Client-to-site VPN
* On-demand access from remote device. Software connects to a VPN concentrator.
* Some software can be configured as always on.
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# 2.7 Internet Connection Types
Sateliete networking
* Communication to a satelite. Non-terrestrial communication
* High cost relative to terrestrial networking: 50 Mbit/s down, 3 Mbit/s are common. Remote sites, difficult-to-network sits.
* High latency: 250 ms up, 250 ms down. Starlink advertises 40 ms and is working on 20 ms.
* High frequencies - 2 GHz. Line of sight. Rain fade.
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# 2.7 Internet Connection Types
Fiber
* High speed data communication. Frequencies of light.
* Higher installation cost than copper: Equipment is more costly. More difficult to repair. Communicate over long distances.
* Large installation in the WAN core: Supports very high data rates. SONET, wavelenth division multiplexing.
* Fiber is slowly approaching the premises. Business and home use.
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# 2.7 Internet Connection Types
Cable broadband
* Broadband: Transmission across multiple frequencies. Different traffic types.
* Data on the "cable: network: DOCSIS (Data Over Cable Service Interface Specification)
* Multiple services: Data, voice, video.
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# 2.7 Internet Connection Types
DSL
* ADSL (Asymmetric Digital Subscriber Line). Uses telephone lines.
* Download speed is faster than the upload speed. (asymmetric) : 200 Mbit/s downstream / 20 Mnit/s upstream are common. 10,000 foot limitation from the central office (CO). Faster speeds may be possible if closer to the CO.
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# 2.7 Internet Connection Types
Cellular networks
* Mobile devices: "cell" phones
* Separate land into "cells": Antenna coverages a cell within certain frequencies.
* Tethering: Turn your phone into wireless router.
* Mobile hotspot: Standalone devices. Use your phone for other things. .
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# 2.7 Internet Connections - Internet Connection Types
WISP
* Wireless Internet Service Provider: Terrestrial internet access using wireless
* Connect rural or remote locations. Internet access for everyone
* Many different deployment technologies: Meshed 802.11, 5G home internet, Proprietary wireless.
* Need an outdoor antenna. Speeds can range from 10 to 1000 megabits per second.
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# 2.7 Internet Connections - Network Types
LAN
* Local Area Network: Local is relative
* A building or group of buildings: High-speed connectivity
* Ethernet and 802.11 wireless: Any slower and it isn't "local"
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# 2.7 Internet connections - Network types
WAN
* Wide Area Network: Spanning the globe
* Generally connects LANs across the distance: And generally much slower than the LAN
* Many different WAN technologies: Point-to-point serial, MPLS, ect. , terrestrial and non-terrestrial
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# 2.7 Internet connections - Network types
PAN
* Personal Area Network: Your own private network. Bluetooth, IR, NFC
* Automobile: Audio output, integrate with phone.
* Mobile phone: Wireless headset
* Health: Workout telemetry, daily reports.
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# 2.7 Internet connections - Network types
MAN
* Metropolitan Area Network: A network in your city. Larger than a LAN, often smaller than a WAN
* Historically MAN-specific topologies: Metro Ethernet
* Common to see government ownership. They "own" the right-of-way.
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# 2.7 Internet connections - Network types
SAN
* Storage Area Network (SAN): Looks and feels like a local storage device. Block-level access. Very efficient reading and writing.
* Requires a lot of bandwidth: May use an isolate network and high-speed network technologies.
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# 2.7 Internet connections - Network types
WLAN
* Wirelss LAN: 802.11 technologies.
* Mobility: Within a building. In a limited geographical area.
* Expand coverage additional access points; Downtown are. Large campus.
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# 2.8 Network Tools
Cable crimpers
* "Pinch" the connector onto a wire: Coaxial, twisted pair, fiber
* Connect the modular connector to the ethernet cable: The final step of the process
* Metal prongs are pushed throught the insulation: The plug is also permanently pressed onto the cable sheath.
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# 2.8 Network Tools
Crimping best-practices
* Get a good crimper: And a good pair of electrician's scissors / cable snips. And a good wire stipper.
* Make sure you use the correct modular connectors: Differences between the wire types.
* Practice, practice, practice. It won't take long to becoming proficient.
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# 2.8 Network Tools
WiFi analyzer
* Wireless networks are increadibly easy to monitor: Everyone "hears" everything.
* Purpose-built hardware or mobile device add-on: Specializes in 802.11 analysis.
* Identify errors and interferences: Validate antenna locaton and installation.
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# 2.8 Network Tools
Tone generator
* Tone generator: Toner probe. Where does that wire go? Follow the tone
* Tone generator: Puts an analog sound on the wire.
* Inductive prone: Doesn't need to touch the copper. Hear through a small speaker.
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# 2.8 Network Tools
Using the tone generator and probe
* Easy wire tracing: Even in complex environments.
* Connect the tone generator to the wire: Modular jack. Coax. Punch down connectors.
* Use the probe to locate the sound: The two-tone sound is easy to find.
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# 2.8 Network Tools
Punch down tool
* "Punch" a wire into a wiring block: 66 block, 110 block, and others.
* Can be tedious: Every wire must be individually punched.
* Trims the wires during the punch. Very efficient process.
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# 2.8 Network Tools
Punch-down best-practices
* Organization is key: Lots of wires. Cable management.
* Maintain your twists: Your category 6A cable will thank you later.
* Document everything. Writted documentation. Tags. Graffiti.
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# 2.8 Network Tools
Cable testers
* Relatively simple: Continuity test. A simple wire map
* Can identiy missing pins: Or crossed wires
* Not usually used for frequency testing: Crosstalk signal loss, etc.
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# 2.8 Network Tools
Loopback plugs
* Useful for testing physical ports: Or fooling your applications.
* Serial / RS-232 (9 pin or 25 pin)
* Network connections: Ethernet, T1, Fiber
* These are not cross-over cables.
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# 2.8 Network Tools
Taps and port mirrors
* Intercept network traffic: Send a copy to a packet capture device
* Physical taps: Disconnect the link, put a tap in the middle. Can be an active or passive tap
* Port mirror: Port redirection, SPAN (Switched Pot ANalyzer). Software-based tap. Limited functionality, but can work well in a pinch.
