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[ Linux Command Manual](#) * * * nslookup (Name Server Lookup) is a network administration tool for querying Domain Name System (DNS) records. It helps users diagnose and resolve DNS-related issues, and is one of the commonly used command-line tools for Linux system administrators and network engineers. The main functions of nslookup include: * Querying the IP address corresponding to a domain name * Querying the domain name corresponding to an IP address (reverse lookup) * Querying specific types of DNS records (MX, NS, SOA, etc.) * Specifying a particular DNS server for queries * * * ## Basic Syntax The basic syntax format of the nslookup command is as follows: nslookup [domain/IP] ### Parameter Description | Parameter | Description | | --- | --- | | domain/IP | The domain name or IP address to query | | DNS server | Specifies the DNS server to use (optional) | ### Common Options | Option | Description | | --- | --- | | `-type=TYPE` | Specifies the query record type, such as A, MX, NS, etc. | | `-debug` | Displays debug information | | `-port=PORT` | Specifies the DNS server port (default 53) | | `-timeout=SEC` | Sets the query timeout time (seconds) | | `-retry=NUM` | Sets the number of retry attempts | * * * ## Usage Examples ### 1. Basic Domain Query Query the A record of a domain (default): nslookup example.com Output example: Server: 8.8.8.8Address: 8.8.8.8#53Non-authoritative answer:Name: example.com Address: 93.184.216.34 ### 2. Specifying a DNS Server for Query Query using Google's public DNS server (8.8.8.8): nslookup example.com 8.8.8.8 ### 3. Querying Specific Record Types Query MX records (mail servers): nslookup -type=MX google.com Query NS records (name servers): nslookup -type=NS google.com Query TXT records: nslookup -type=TXT google.com ### 4. Reverse DNS Lookup (IP to Domain) nslookup 8.8.8.8 ### 5. Interactive Mode Enter nslookup without parameters to enter interactive mode: ## Example nslookup >set type=MX > google.com > server 8.8.4.4 > example.com >exit * * * ## Common DNS Record Types | Record Type | Description | Example Command | | --- | --- | --- | | A | IPv4 address record | `nslookup -type=A example.com` | | AAAA | IPv6 address record | `nslookup -type=AAAA example.com` | | MX | Mail exchange record | `nslookup -type=MX example.com` | | NS | Name server record | `nslookup -type=NS example.com` | | CNAME | Canonical name record | `nslookup -type=CNAME www.example.com` | | TXT | Text record | `nslookup -type=TXT example.com` | | SOA | Start of authority record | `nslookup -type=SOA example.com` | * * * ## Advanced Usage ### 1. Debug Mode nslookup -debug example.com ### 2. Querying DNS Root Servers nslookup -type=NS . ### 3. Querying a Specific Port nslookup -port=8053 example.com dns-server.example.com ### 4. Setting Timeout and Retry nslookup -timeout=10 -retry=3 example.com * * * ## Common Problem Resolution ### 1. Query Has No Response Possible causes: * Network connection issues * DNS server unavailable * Firewall blocking DNS queries (port 53) Solutions: ## Example # Check network connection ping 8.8.8.8 # Try another DNS server nslookup example.com 8.8.8.8 ### 2. What Does "Non-authoritative answer" Mean? It indicates that the returned result comes from a DNS cache rather than an authoritative DNS server. To obtain an authoritative answer, you need to query the authoritative DNS server for that domain. ### 3. How to Query the Authoritative DNS Server for a Domain? nslookup -type=NS example.com * * * ## Alternative Tools Although nslookup is still widely used, modern Linux systems prefer to recommend `dig` or `host` commands: 1. **dig** - A more powerful DNS query tool dig example.com 2. **host** - A simpler DNS query tool host example.com * * * ## Summary nslookup is a simple and practical DNS query tool. Through this tutorial, you should be able to: 1. Understand the basic usage and common options of nslookup 2. Query various types of DNS records 3. Diagnose basic DNS-related issues 4. Understand the differences between nslookup and other DNS tools The best way to master nslookup is through practice. Try querying websites you frequently visit, or your organization's domain name servers, and observe the results returned by different types of DNS records. * * Linux Command Manual](#)