Article Issue #5234

DDNS (Dynamic DNS)

What to know

DDNS (Dynamic DNS) is a system that maintains the mapping between a human-readable domain name and a frequently changing IP address, typically used by home internet subscribers whose ISP assigns a new public IP address periodically; A DDNS client (such as ddclient, inadyn, or a router's built-in DDNS support) polls the server's current public IP at regular intervals (typically every 5 minutes) by querying an IP detection service (ifconfig.me, icanhazip.com, etc.) or reading the WAN IP directly from the router; DDNS is the traditional solution for home server accessibility and is still relevant for ISPs that assign real (non-CGNAT) public IPs

Wikiwalls Team Administrator

May 15, 2026 2 min read

« Back to Glossary Index

DDNS (Dynamic DNS) is a system that maintains the mapping between a human-readable domain name and a frequently changing IP address, typically used by home internet subscribers whose ISP assigns a new public IP address periodically. A DDNS client runs on the home router or server, detects IP changes, and updates the DNS record via an API call to the DDNS provider. This allows a consistent hostname like home.example.duckdns.org to always resolve to the current home IP without manual DNS updates.

How it works

A DDNS client (such as ddclient, inadyn, or a router’s built-in DDNS support) polls the server’s current public IP at regular intervals (typically every 5 minutes) by querying an IP detection service (ifconfig.me, icanhazip.com, etc.) or reading the WAN IP directly from the router. If the IP has changed since the last update, the client calls the DDNS provider’s update API (each provider has a different endpoint format) with the new IP. The DDNS provider sets the DNS record’s TTL to a low value (60 to 300 seconds) to minimize the window during which the old IP is cached.

Key facts

Free providers: DuckDNS, No-IP (free tier), and Dynu offer free DDNS subdomains with API-based updates
Cloudflare alternative: Builders using Cloudflare DNS can run a cloudflare-ddns Docker container to achieve the same effect with their own domain at no extra cost
CGNAT limitation: DDNS does not help when the ISP assigns a private IP behind CGNAT rather than a real public IP; Cloudflare Tunnel or Tailscale are the solutions in that case

For builders

DDNS is the traditional solution for home server accessibility and is still relevant for ISPs that assign real (non-CGNAT) public IPs. For builders on modern residential ISPs that use CGNAT (increasingly common), DDNS is ineffective because there is no public IP to map to. Checking whether the home IP is actually public (compare the router WAN IP to the result of ipinfo.io) is the first diagnostic step before investing in a DDNS setup.