Chapter 1: Networking Fundamentals
Hello, friends! Before launching any server on the cloud, let's understand how computers find each other and how they talk. Security groups, VPC, subnets, Elastic IP, load balancers – all these cloud concepts stand on basic networking. In my class many students want to jump straight to EC2, but I always say: networking first, then cloud. In this chapter we take one example along: a dairy brand like Amul (sample data, for practice) – its order website, its office Wi-Fi and, later, a VPC on AWS. If this chapter is clear, AWS networking will feel very simple.
नमस्कार मित्रांनो! क्लाउडवर कोणताही सर्व्हर लॉन्च करण्याआधी आपण हे समजून घेऊया की कॉम्प्युटर्स एकमेकांना कसे शोधतात आणि कसे बोलतात. सिक्युरिटी ग्रुप्स, VPC, सबनेट्स, Elastic IP, लोड बॅलन्सर्स – हे सगळे क्लाउड कॉन्सेप्ट्स बेसिक नेटवर्किंगवरच उभे आहेत. माझ्या क्लासमध्ये बऱ्याच स्टुडंट्सना डायरेक्ट EC2 वर जायचं असतं, पण मी नेहमी सांगतो: आधी नेटवर्किंग, मग क्लाउड. या चॅप्टरमध्ये आपण एक उदाहरण सोबत घेऊ: Amul-style dairy (सॅम्पल डेटा, सरावासाठी) – त्यांची ऑर्डर वेबसाइट, ऑफिसचं Wi-Fi आणि पुढे AWS वर VPC. हा चॅप्टर नीट समजला तर AWS नेटवर्किंग एकदम सिंपल वाटेल.
नमस्ते दोस्तों! क्लाउड पर कोई भी सर्वर लॉन्च करने से पहले हम ये समझ लेते हैं कि कंप्यूटर्स एक-दूसरे को कैसे ढूँढते हैं और कैसे बात करते हैं. सिक्योरिटी ग्रुप्स, VPC, सबनेट्स, Elastic IP, लोड बैलेंसर्स – ये सारे क्लाउड कॉन्सेप्ट्स बेसिक नेटवर्किंग पर ही खड़े हैं. मेरी क्लास में बहुत से स्टूडेंट्स को सीधे EC2 पर जाना होता है, लेकिन मैं हमेशा कहता हूँ: पहले नेटवर्किंग, फिर क्लाउड. इस चैप्टर में हम एक उदाहरण साथ लेंगे: Amul-style dairy (सैंपल डेटा, सिर्फ़ अभ्यास के लिए) – उनकी ऑर्डर वेबसाइट, ऑफ़िस का Wi-Fi और आगे AWS पर VPC. ये चैप्टर ठीक से समझ आ गया तो AWS नेटवर्किंग बिल्कुल सिंपल लगेगी.
What you will learn in this chapter
- Why networking matters on AWS
- IP addresses, ports and sockets
- IPv4, CIDR and subnetting
- IPv6 format and shortening
- Static vs dynamic IP
- Public vs private IP and NAT
- How it all maps to a VPC
Concepts in this chapter
- 1.1Why networking matters in the cloud
- 1.2IP address — what and why
- 1.3Ports
- 1.4IPv4 in detail
- 1.5IPv6
- 1.6Static vs dynamic IP
- 1.7Public vs private IP
- 1.8NAT (Network Address Translation)
- 1.9How these concepts map to AWS
Review and practice
Extended teaching notes
Why this lesson matters
Cloud security is mostly IAM, network exposure, logging and secure defaults. The shared responsibility model means the provider patches the metal; you patch what you configure.
- No public databases or public admin panels.
- Roles / OIDC instead of long-lived access keys.
- CloudTrail / Activity Logs / Audit Logs on and retained.
- S3/Blob/GCS: Block Public Access; encrypt; least privilege.
Mini case study
Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.
Defender's worksheet (do this today)
- Write the lesson title, date and the exact lab target you are allowed to use.
- List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
- Run one safe check from the lesson on a lab system only. Paste the command and output.
- Write a two-sentence fix you would give a teammate.
- Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.
Indian workplace (sample data)
Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).
Global practice
Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.
Everyday analogy
Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.
Key terms
- Control: a safeguard (patch, config, process, detection).
- Finding: a weakness backed by evidence.
- Remediation: the fix plus how you verified it.
- Scope: systems you have written permission to touch.
- Least privilege: only the access the task needs.
- Defence in depth: several layers so one failure does not end the story.
Common mistakes
- Skipping written permission "just for a quick scan".
- Practising on hostel, office or public targets without authorisation.
- Collecting tool output without writing the fix.
- Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
- Publishing screenshots that contain secrets, cookies or internal hostnames.
Recap
- Evidence, fix, owner, date.
- Own lab only.
- Fix > spectacle.
Practice Tasks
Paris Fashion Hub is a fashion business in Paris. Camille Laurent looks after its IT and cloud work. They count money in EUR and run their AWS resources in the eu-west-3 Region. In the tasks below you do real jobs for them using what this lesson teaches. All names, account IDs, IP addresses and numbers are made up for practice.
0 / 12
Easy How many addresses in a /16?
Why: Picking a VPC size needs this count.
What to do: Paris Fashion Hub plans the VPC 10.145.0.0/16. How many IP addresses does it hold in total?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Easy Create a VPC
Why: A VPC is your own private network in AWS. Everything else lives inside it.
What to do: Create a VPC with the CIDR block 10.6.0.0/16.
- Read the task and decide which AWS service it is about.
- Write aws, then the service name, then the operation (the action word).
- Add each needed flag (--name) followed by its value from the task.
- Flags can be in any order. Click Check answer.
Easy Test a website from the server
Why: curl shows whether the web server answers, even before DNS is ready.
What to do: Request http://localhost and show only the response headers.
- Find the Linux command that does this job.
- Add the options (like -r or -h) the task needs.
- Add the file names, folders or users in the right order.
- Use sudo if the job changes system files or users. Click Check answer.
Medium First usable IP for a server
Why: The first 4 addresses are reserved by AWS.
What to do: What is the first IP address a server can get in 10.145.20.0/24 on AWS?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Find the VPC router address
Why: AWS reserves base+1 for the router.
What to do: Which address does AWS reserve for the VPC router in subnet 10.145.4.0/24?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Usable IPs in an AWS /24 subnet
Why: AWS keeps 5 addresses in every subnet.
What to do: How many addresses can Paris Fashion Hub use for servers in subnet 10.145.1.0/24 on AWS?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Usable IPs in a /28
Why: /28 is the smallest AWS subnet.
What to do: Subnet 10.145.9.0/28 on AWS. How many usable IPs?
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Medium Create a subnet in one AZ
Why: Subnets split the VPC range and each one lives in exactly one AZ.
What to do: In vpc-01af0ffe22deadbee, create subnet 10.6.1.0/24 in eu-west-3a.
- Read the task and decide which AWS service it is about.
- Write aws, then the service name, then the operation (the action word).
- Add each needed flag (--name) followed by its value from the task.
- Flags can be in any order. Click Check answer.
Medium Do these VPCs overlap?
Why: Peering fails when ranges overlap.
What to do: Can VPC 10.145.0.0/16 peer with VPC 10.145.128.0/17? Answer yes or no.
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Hard Range of a /26
Why: Knowing the range stops subnets from overlapping.
What to do: Write the first and last address of 10.145.3.64/26 (like a.b.c.d - e.f.g.h).
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Hard Pick the smallest prefix
Why: Right-sizing saves address space.
What to do: A subnet must hold 100 servers on AWS. What is the largest prefix number (smallest subnet) that fits? Answer like /25.
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.
Hard Split a /24 into two
Why: Public and private subnets often split one block.
What to do: Split 10.145.8.0/24 into two equal subnets. Write both CIDRs separated by a comma.
- Write down the numbers the task gives you.
- Work it out step by step on paper.
- Type only the final answer in the box.
- Click Check answer.