Reverse DNS lookup facts for kids
Reverse DNS lookup, often called rDNS, is like looking up a phone number in a special phone book. Instead of finding a phone number (an IP address) from a name (a domain name), you do the opposite! You start with a phone number (an IP address) and find out the name (the hostname) that belongs to it.
Think of it this way: When you type a website address like `www.example.com` into your browser, the Domain Name System (DNS) helps your computer find the special number (IP address) for that website. This is like looking up a person's phone number when you know their name.
Reverse DNS lookup does the opposite. If you have an IP address, rDNS helps you find the website name or computer name connected to it. It's like having a phone number and wanting to know whose number it is.
Contents
What is an IP Address?
An IP address is a unique number that identifies a computer or device on the internet or a local network. It's similar to a street address for your house, but for computers. For example, `192.0.2.1` could be an IP address.
What is a Hostname?
A hostname is a label that identifies a device on a network. It's usually a name that humans can easily remember, like `www.example.com` or `mycomputer`. Hostnames are much easier to remember than long strings of numbers like IP addresses.
How Does Reverse DNS Work?
Reverse DNS lookup uses special records in the Domain Name System called PTR records. PTR stands for "Pointer" record. These records point from an IP address back to a hostname.
When a computer wants to do a reverse DNS lookup, it asks a special DNS server for the PTR record linked to an IP address. The server then replies with the hostname if it finds a match.
Why is Reverse DNS Important?
Reverse DNS lookups are used for several important reasons on the internet:
- Email Servers: Many email servers use rDNS to check if incoming emails are from legitimate (real and trusted) sources. If an email comes from an IP address that doesn't have a matching rDNS entry, it might be marked as spam or blocked.
- Logging and Analytics: Websites and servers often use rDNS to record the hostnames of visitors. This helps them understand where their visitors are coming from and makes their log files easier to read.
- Network Troubleshooting: When network problems happen, rDNS can help network administrators figure out which devices are connected to specific IP addresses, making it easier to find and fix issues.
- Security: Some security systems use rDNS to verify the identity of a connection. For example, if a server expects a connection from a specific hostname, it can use rDNS to confirm that the IP address matches that hostname.
Matching Records: A and PTR
For everything to work smoothly on the internet, it's important that the regular DNS records (called "A records," which map hostnames to IP addresses) and the reverse DNS records (PTR records) match up. This means if `www.example.com` points to `192.0.2.1` (A record), then `192.0.2.1` should point back to `www.example.com` (PTR record). This helps keep the internet organized and secure.
Related pages
See also
In Spanish: Búsqueda DNS inversa para niños
