VPC AND SUBNETS CIDR CLACUALTION

Yes 👍 bilkul le sakte ho — /16 VPC ke andar /18 subnet valid hai ✅ Bas 2 rules follow hone chahiye: ✅ 1. Rule Check 🔹 VPC: 172.31.0.0/16 🔹 Subnet: 172.31.0.0/18 ✅ VALID ✔ Smaller (more specific) than /16 ✔ Inside VPC range ✔ No overlap (agar dusra subnet same range use na kare) 🧠 2. /18 ka matlab kya hota hai? /18 = 4096 IPs Range example: 172.31.0.0/18 → 172.31.0.0 to 172.31.63.255 📊 3. /16 ko /18 me divide karte hain Ek /16 VPC ko tum 4 subnets (/18) me tod sakte ho: 1. 172.31.0.0/18 → 0 – 63 2. 172.31.64.0/18 → 64 – 127 3. 172.31.128.0/18 → 128 – 191 4. 172.31.192.0/18 → 192 – 255 👉 Ye sab non-overlapping hai ✅ ❌ 4. Kab problem aayega? Agar tum already ek subnet bana chuke ho: 172.31.16.0/20 👉 Then: 172.31.0.0/18 ❌ (overlap karega) Kyuki: /18 range: 0 – 63 /20 range: 16 – 31 👉 Overlap ho gaya → AWS reject karega 🔥 5. Real Interview Tip 👉 Technically /18 allowed hai 👉 BUT real world me: ✔ /24 → best practice ✔ /18 → too large (waste of IPs) 🎯 Final Answer (Short) ✔ Yes, /18 le sakte