Networking Refresher
1. IP Addresses
Display IP address in Linux : $ ifconfig
We communicate over Layer 3 (Router)
NAT \(\to\) Network Address Translation
1.2. Private IP addresses
| Network class | Network numbers | Network mask | Number of networks | Number of hosts per network |
|---|---|---|---|---|
| Class A | 10.0.0.0 | 255.0.0.0 | 126 | 16,646,144 |
| Class B | 172.16.0.0 to 172.32.0.0 | 255.255.0.0 | 16,383 | 65,024 |
| Class C | 192.168.0.0 to 192.168.255.255 | 255.255.255.0 | 2,097,151 | 254 |
| Loopback | 127.0.0.1 to 127.0.0.7 | 255.255.255.255 | - | - |
2. MAC Addresses
MAC \(\to\) Media Access Control
NIC \(\to\) Network Interface Card
Mac address lookup : first 3 pairs are identifiers
Layer 2, related to switching (Switch)
3. TCP, UDP and the Three-Way Hanshake
Layer 4
TCP \(\to\) Transmission Control protocol
UDP \(\to\) User Datagram Protocol
3.1. TCP 3-way handshake
4. Common ports and protocols
65,535 ports total \(\to\) 1024 "well-known" ports
FTP \(\to\) File Transfer Protocol
Telnet \(\to\) Log remotely to a machine
SSH \(\to\) Secure SHell (encrypted telnet)
SMTP, IMAP, POP3 \(\to\) all relate to mail
DNS \(\to\) Domain Name System
SMB \(\to\) File shares (Samba)
SNMP \(\to\) Simple Network Management Protocol
| Protocol | Port |
|---|---|
| FTP | 21 |
| SSH | 22 |
| Telnet | 23 |
| SMTP | 25 |
| DNS | 53 |
| HTTP | 80 |
| HTTPS | 443 |
| POP3 | 110 |
| SMB | 139 + 445 |
| IMAP | 143 |
| RDP | 3389 |
| Protocol | Port |
|---|---|
| DNS | 53 |
| DHCP | 67, 68 |
| TFTP | 69 |
| SNMP | 161 |
5. The OSI model
- Physical \(\to\) data, cables, cat6
- Data \(\to\) Switching, MAC addresses
- Network \(\to\) IP addresses, routing
- Transport \(\to\) TCP/UDP
- Session \(\to\) session management
- Presentation \(\to\) WMV, JPEG, MOV
- Application \(\to\) HTTP, SMTP
6. Subnetting
Subnetting Cybermentor Excel Cheatsheet
Link to site IP Address Guide
