nslookup

---

• May start investigating a name resolution issue by verifying the name configured on a host
  • in Windows:
    • use ipconfig /all to display the FQDN of the local host
  • in Linux:
    • use hostname --fqdn

Info

• on a local network, each host is normally configured with a DNS suffix
• e.g., PC1 might be configured as part of a Windows network with the suffix ad.example.local
• if this suffix is not set correctly, some name queries could fail

• Can troubleshoot DNS name resolution with nslookup:
  • nslookup -Option Host DNSServer
    • host can be either a host name, domain name, FQDN, or IP address
    • DNSServer is the IP address of a server used to resolve the query
      • default server is used if omitted
    • Option specifies subcommand
    • E.g., querying Google’s public DNS server for information about 515support.com’s mail records:
      • nslookup -type=mx 515support.com 8.8.8.8
  • if run without arguments (or just the specified server),
    • tool is started in interactive mode
    • can perform specific query types and output result to text for analysis

Info

• Windows PowerShell environment provides a more sophisticated scripted environment that can be used to issue cmdlets to test DNS name resolution
• PowerShell provides a cmdlet called Resolve-DnsName
  • a more flexible method of testing a name resolution
  • allows testing of the different methods of name resolution
    • i.e., HOSTS files, DNS cache, DNS server