Networking Refresher
Last updated
Last updated
IP Addresses
MAC Addresses
TCP, UDP, and the Three-Way Handshake
Common Ports and Protocols
The OSI Model
Subnetting
Layer 3 - Network
IP (Internet Protocol) addresses, IPv4 and IPv6 - core internet addressing protocols, operating on layer 3 of OSI model.
IPv4: 192.168.0.1 - decimal notation
4 octets of 8 bits = 32 bits
Total IPv4 addresses:
IPv6: 2001:0db8:85a3:0000:0000:8a2e:0370:7334 - hexadecimal notation
8 groups of 16 bits = 128 bits
Total IPv6 addresses:
Key IPv6 improvements:
Enhanced security
Simplified network configuration
More efficient routing
Transition challenges:
IPv4 and IPv6 not directly compatible
Ongoing global shift from IPv4 to IPv6
Critical for sustaining internet growth and accommodating future devices
Displays the network interface configuration and status:
Layer 2 - Data Link
MAC (Media Access Control) address - unique identifier assigned to network interface controllers (NICs) of network devices.
MAC Address: 00:1A:2B:3C:4D:5E - hexadecimal notation
6 pairs of hexadecimal digits = 48 bits:
First 3 pairs: Manufacturer identifier
Last 3 pairs: Unique device identifier
Lookup devices using the first 3 pairs: https://www.macvendorlookup.com
Layer 4 - Transport
TCP (Transmission Control Protocol) and UPD (User Datagram Protocol) - transport layer protocols in computer networks.
TCP:
Connection-oriented
Reliable, ordered, error-checked delivery
Uses acknowledgment, retransmission, and flow control
Breaks data into packets with sequence numbers
Suitable for: web browsing, email, file transfer, remote login
UDP:
Connectionless
Simpler and lightweight
No guaranteed delivery or packet order
Suitable for: streaming media, online gaming, DNS, VoIP
Three-Way Handshake - establishes TCP connections:
SYN: Client sends SYN packet with initial sequence number
SYN-ACK: Server responds with SYN-ACK packet, own sequence number
ACK: Client acknowledges with ACK packet, incremented sequence number
Capture Packet Data using Wireshark:
TCP Protocols:
FTP (File Transfer Protocol)
21
SSH (Secure Shell)
22
Telnet
23
SMTP (Simple Mail Transfer Protocol)
25
HTTP (Hypertext Transfer Protocol)
80
HTTPS (Hypertext Transfer Protocol Secure)
443
POP3 (Post Office Protocol version 3)
110
IMAP (Internet Message Access Protocol)
143
RDP (Remote Desktop Protocol)
3389
SMB (Server Message Block)
445
FTPS (FTP over SSL/TLS)
990
MySQL
3306
UDP Protocols:
DHCP (Dynamic Host Configuration Protocol)
67, 68
SNMP (Simple Network Management Protocol)
161
NTP (Network Time Protocol)
123
TFTP (Trivial File Transfer Protocol)
69
Protocols using both TCP and UDP:
DNS (Domain Name System)
53
LDAP (Lightweight Directory Access Protocol)
389
OSI (Open Systems Interconnection) model - conceptual framework standardizing communication system functions into seven distinct layers.
key aspects:
Separates complex network communication into manageable layers
Facilitates interoperability and troubleshooting
Conceptual model, not always reflecting exact implementations
Useful reference for understanding network communication
Subnetting - Process of dividing a network into smaller subnetworks
CIDR (Classless Inter-Domain Routing) - Method to represent IP addresses and subnet masks
Concepts:
Borrows bits from host portion to create subnet identifier
Allows efficient use of IP addresses
Facilitates network management and routing
CIDR Notation:
Format: IP address/prefix length
Example: 192.168.0.0/24
First 24 bits: Network portion
Remaining 8 bits: Host portion
Subnetting example:
Subnet Mask
255.255.255.0
Subnetting (borrowing 2 bits):
1
192.168.0.0 - 192.168.0.63
192.168.0.0/26
2
192.168.0.64 - 192.168.0.127
192.168.0.64/26
3
192.168.0.128 - 192.168.0.191
192.168.0.128/26
4
192.168.0.192 - 192.168.0.255
192.168.0.192/26
New Subnet Mask: 255.255.255.192
Benefits:
Flexible network boundaries
Efficient address allocation
Enhanced network organization
Subnetting Sheet:
Bits Sheet:
How to calculate the Subnet:
