Network Testing: Core Networking (Foundation) part 3

Network Testing: Core Networking (Foundation) part 3 | by JEETPAL | in OSINT Team - Freedium Milestone: 20GB Reached We’ve reached 20GB of stored data — thank you for helping us grow! Patreon Ko-fi Liberapay Close < Go to the original Network Testing: Core Networking (Foundation) part 3 Hi, JEETPAL Follow OSINT Team · ~3 min read · April 1, 2026 (Updated: April 1, 2026) · Free: Yes I am starting a Network testing blog writeups series from basic. So, Let's get started This is part 3 you can get part 2 here Network Testing: Core Networking (Foundation) part 2 credit: centraleyes.com Topics covers: Subnet masking/CIDR DHCP VPN/OpenVPN So, Let get started with first concept subnet masking/CIDR ( Classless Inter-Domain Routing) . As Earlier in part 1 covers What is IP and how this work. I will now tell you how subnet masking work. If you have tested any CIDR or seen the scope of any Hackerone program, it has 123.234.255.0/24 //Random IP So, what does this actually mean? here the IP are 32 bits each octet contains 8 bits of number for example above is 123 = 8 Bits 234 = 8 Bits 255 = 8 Bits and in last it has 0/24 This the first 24 Bits are fixed part of a network and cannot be assign to any device. It only can assign IP such as 123.234.255.X to any device range from 1 to 254 here mostly 1 are your router device and last IP 123.234.255.255 is assigned to broadcast for their work. We can count how many hosts in bits can have for example Number of IPs = 2^(32 - CIDR) Here CIDR is /24. so this will be IPs = 2^(32-24) IPs = 2^(8) IPs= 256 So, an CIDR with /24 can have 256 IPs in it, but we have to subtract the network IP and broadcast IP, so it becomes 254 IPs in a range. Same goes with /16 Here the last 2 octet will change 123.234.X.X this is used for company with many devices as this make a large number of IPs. So how we discover IPs in subnet? We use netdiscover and other tools to discover the host in a particular IP system for example Command to scan a CIDR Output of the command Now it comes to DHCP. It is pool of IPs when a device enters into network DHCP assign the device an IPs from the pool of IPs he has. A device can also set it IP manual but mostly DHCP is used to assign an IP. Wifi settings Settings of manual IP Here you can assign yourself any IP you want but make sure it is unsued in your network in subnet you have the put the value of your subnet for example 255.255.255.0 You can get it from running ipconfig in your cmd or ifconfig in your Linux CMD Now let's move on to VPN. VPN (Virtual Private Network) creates a secure encrypted tunnel for data transfer. It changes your public IP to the VPN server's IP and encrypts your traffic. It helps in connecting to websites without exposing your real IP. OpenVPN is a VPN protocol that uses configuration files (.ovpn) which include details like server address, port, protocol, and certificates to securely connect to a VPN server. Thank you! Connect with me Linkedin : https://www.linkedin.com/in/jeet-pal-22601a290/ Instagram: https://www.instagram.com/jeetpal.2007/ X/Twitter: https://x.com/Mr_mars_hacker And here's something special for you! 🚨 Join a community of 3 ,600+ security researchers on our Discord server , where we discuss Web3 vulnerabilities, audits, and much more! 🚀 👉 Join the server here!: https://discord.gg/Y467qAFM4X #networkpentesting #bug-bounty #cybersecurity #red-team #network-basics Reporting a Problem Sometimes we have problems displaying some Medium posts. If you have a problem that some images aren't loading - try using VPN. Probably you have problem with access to Medium CDN (or fucking Cloudflare's bot detection algorithms are blocking you).