Why IP Addressing Matters
Every Azure resource that communicates over a network needs an IP address.
Azure provides both private IPs (inside VNets) and public IPs (for internet access). Correct IP planning ensures connectivity, security, and cost efficiency.
Types of IP Addresses
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Private IPs
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Used for communication within a VNet.
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Never exposed to the public internet.
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Assigned dynamically by default, but can be set as static if required.
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Public IPs
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Used to communicate with the internet.
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Needed for inbound access (e.g., RDP to a VM, public website).
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Can be Basic (legacy, less features) or Standard (recommended, zone-redundant, secure by default).
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Dynamic vs Static Assignment
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Dynamic IP = automatically assigned from Azure’s pool when a resource starts. May change if resource is stopped/deallocated.
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Static IP = manually reserved, always remains the same.
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Exam trick: If the scenario requires a fixed IP for DNS or firewall rules, always pick Static.
IP Address Space Planning
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VNets use private IP ranges (RFC 1918): 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
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When creating a VNet, you must define its CIDR block (e.g., 10.1.0.0/16).
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Subnets carve out smaller ranges from the VNet.
DNS in Azure
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By default, Azure provides a built-in DNS resolver for name resolution within VNets.
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You can configure custom DNS servers (e.g., on-prem DNS) if required.
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Azure DNS (separate service) lets you host public DNS zones for custom domains.
Confusion Buster 🚨
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Azure DNS vs Default Resolver
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Default = internal resolution inside a VNet.
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Azure DNS = public-facing DNS for your domains.
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Public IP vs Private IP
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Public IP = reachable over internet.
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Private IP = internal-only.
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Exam trick: A VM can have both, but traffic rules differ.
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Simple Example
A web server VM gets:
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Private IP: 10.1.1.4 (used for communication with database in the same VNet).
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Public IP: 52.168.15.22 (used by customers to access the website).
DNS resolveswww.myapp.com→ Public IP, while internal apps use Private IP for database queries.
Exam Tip
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If the question mentions fixed IP for firewall rules → Static IP.
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If it mentions name resolution for internal resources → Default Azure DNS.
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If it mentions hosting a company domain → Azure DNS service.
What to Expect in the Exam
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Direct Q: “Which type of IP is required for a resource that must be reachable over the internet?” → Public IP.
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Scenario: “You need a VM’s IP to remain the same after restart.” → Static IP.
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Trick Q: “Azure DNS can resolve names between VNets by default.” (False — you may need custom DNS or Private DNS zones).