What is DNS
DNS (Domain Name System) is a distributed domain name system that translates human-readable domain names (for example, rechecker.ru) into server IP addresses (217.114.13.253) that computers can understand.
DNS is often called the “phone book of the internet.” When you enter a website address in your browser, a DNS query finds the corresponding IP address, and only then does the browser connect to the server.
Without DNS, you would have to remember the IP addresses of all websites. DNS is one of the fundamental technologies of the internet and has existed since 1983.
How DNS works
The DNS query process:
- Browser checks its local DNS cache
- OS checks the
hostsfile and its own cache - Recursive resolver (the ISP’s server or 8.8.8.8) processes the query
- Root DNS servers (13 servers worldwide) point to TLD servers
- TLD servers (for .ru, ru-center) point to the domain’s NS servers
- Domain NS servers return the required record
- The response is cached for the duration of the TTL
The entire process usually takes 20-120 ms.
Types of DNS records
A record — IPv4 address
example.com. 3600 IN A 93.184.216.34
Maps a domain to a server’s IPv4 address.
AAAA record — IPv6 address
example.com. 3600 IN AAAA 2606:2800:220:1:248:1893:25c8:1946
Maps a domain to an IPv6 address.
CNAME record — alias
www.example.com. 3600 IN CNAME example.com.
Redirects one domain to another (an alias).
MX record — mail
example.com. 3600 IN MX 10 mail.example.com.
Specifies the mail servers for a domain. The number (10) is the priority.
TXT record — text data
example.com. 3600 IN TXT "v=spf1 include:_spf.google.com ~all"
Used for SPF, DKIM, DMARC, and domain verification.
NS record — name servers
example.com. 86400 IN NS ns1.example.com.
Specifies the DNS servers authoritative for a domain.
SOA record — start of authority
Contains information about the DNS zone: primary NS, administrator’s email, serial number, and TTL.
TTL — Time To Live
TTL (in seconds) is how long a DNS record is cached. Standard values:
- 300 (5 minutes) — for records that change frequently
- 3600 (1 hour) — standard
- 86400 (24 hours) — for stable records
When planning a server change, lower the TTL in advance to 300 — then changes will propagate faster.
Check DNS on reChecker
Use DNS Lookup to fully analyze a domain’s DNS records. The tool will show:
- All A, AAAA, CNAME, MX, TXT, and NS records
- TTL values for each record
- SPF and DMARC configuration
- DNS response time
FAQ
How long does a DNS change take? DNS changes propagate within 24-48 hours (DNS propagation). The actual time depends on the records’ TTL: if the TTL was 86400, ISP caches can persist for up to 24 hours. To speed things up, lower the TTL to 300 48 hours before the change.
What is the difference between an A record and a CNAME? An A record points directly to an IP address. A CNAME points to another domain name (an alias). CNAME is convenient for subdomains and CDNs because the IP does not need to be updated. But a CNAME cannot be used for the root domain (apex domain) — only A or ALIAS.
What is DNS over HTTPS (DoH)? DoH encrypts DNS queries over HTTPS so that your ISP cannot see which websites you visit. It is supported in Chrome, Firefox, and Windows 11. Cloudflare provides a DoH server: 1.1.1.1.