NSLookup allows you to retrieve additional information from the Internet Domain Name System by sending querries to your default Name Server, or an alternate Name Server you specify. Enter the domain name in the "Query Name" field, and select the type of query using the "Query Type" popup menu.
To convert between an IP address and a domain name, you can also use the IP Address and Name fields with the lookup button (small magnifying glass) in many of the IPNetMonitor windows. This will use the domain name system recursively (by calling the local Resolver) to find the corresponding name or address. NSLookup querries the default or specified Name Server directly, and may not return an answer if the Name Server does not have the information requested and does not support recursion to automatically pass the query to the next authoritative Name Server.
If you enter an email address of the form <username>@<host>, NSLookup will convert it to <username>.<host> per domain name convention. If you enter a dotted quad IP address of the form <AA.BB.CC.DD>, NSLookup will convert it to <DD.CC.BB.AA>.IN-ADDR.ARPA per domain name convention. To lookup the host name for an IP address, enter the IP address as a dotted quad and select "Pointer" as the query type.
To find the domain names registered to an organization, first lookup the name servers for that organization (for example, lookup "apple.com" with query type Name Server), then copy the IP address of a name server to the "Query Name" field and select query type List Domains (uses Start of Authority followed by a Zone Transfer).
Name Servers respond to querries with zero or more matching resource records. For each record received, NS Lookup will show the resource name, resource type, Time To Live (TTL), and any resource data based on the type of record received. A response may also include additional records specifying authoritative Name Servers for the requested domain, and the IP address of the name server (intended to reduce the need for additional lookups).
Using NSLookup, WhoIs, and Finger, you can often determine the original source of unsolicited email containing forged headers (SPAM) and request the parties involved to take appropriate corrective action. See <http://www-fofa.concordia.ca/spam/> for more information.
If you have Internet Config installed, you can make IPNetMonitor a helper application for URLs of the form <nslookup:ultranet.com/NS> (lookup name servers for "ultranet.com") or <nslookup:www.sustworks.com/CNAME/ns2.ma.ultra.net> (lookup canonical name for "www.sustworks.com" from name server ns2.ma.ultra.net).
When you invoke one window from another, the corresponding data is automatically transferred. Invoke the Ping window from the Window menu (Cmd-T) to begin a ping test to the Name Server address.
A popup history menu keeps a list of Recent Name Servers. The content of the Server Name field is added to the history menu when a test to that name is invoked. The Server Name or Address field is added to the history menu when the Lookup button is pressed. If the menu becomes full (10 entries), the least recently used item will be replaced. To remove an item from the history menu, select that item while pressing the Option key.
Keyboard Shortcuts:
Cmd-Period Abort a test or lookup in progress
Cmd-L Open another NSLookup window
Cmd-T Ping Name Server
Cmd-R Trace Route to Name Server
Cmd-K Test Link Rate to this address
Cmd-B Transfer Name Server address to Subnet Calculator
