networking:dns
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Table of Contents
DNS Explained
The Domain Name System (DNS) is like the phonebook of the internet. It translates human-readable domain names (like `example.com`) into IP addresses (like `93.184.216.34`) that computers use to communicate.
How DNS Works
When you type a domain name in your browser, a series of queries happens:
1. **Resolver** (your ISP or public DNS like 8.8.8.8) receives the query 2. **Root Server** tells which TLD server to ask 3. **TLD Server** (.com, .org, .ir) tells which authoritative server to ask 4. **Authoritative Server** provides the final answer
DNS Record Types
| Record Type | Purpose | Example |
|---|---|---|
| A | Maps domain to IPv4 address | `example.com → 93.184.216.34` |
| AAAA | Maps domain to IPv6 address | `example.com → 2606:2800:220:1:248:1893:25c8:1946` |
| CNAME | Alias (canonical name) | `www.example.com → example.com` |
| MX | Mail exchange server | `mail.example.com` |
| TXT | Text records (SPF, DKIM, etc.) | `v=spf1 include:_spf.example.com ~all` |
| NS | Name server | `ns1.example.com` |
| SOA | Start of authority (zone info) | `ns1.example.com admin.example.com 2026072001` |
What is an Authoritative Server?
An authoritative DNS server is the final authority for a domain's DNS records. It holds the “official” records that are published in the DNS zone file.
Example:
| Domain | Authoritative Server | Records |
| ——– | ——————— | ——— |
| `example.com` | `ns1.example.com` | A → `93.184.216.34` |
| MX → `mail.example.com` | ||
| TXT → `v=spf1 include:_spf.example.com ~all` |
Or visually:
example.com
└── authoritative: ns1.example.com
├── A → 93.184.216.34
├── MX → mail.example.com
└── TXT → v=spf1 include:_spf.example.com ~all
Telenegar DNS Check
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