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Lookup is used to convert between IP Addresses and Domain Names. Enter the name or address you wish to lookup and press return. Lookup uses the domain name system recursively by calling the local Resolver to find the corresponding name or address.

After translating a name-to-address or address-to-name, the verification field shows the reverse lookup of the result. Normally this will be the same as the original target, but might be different if there is more than one name for the same address or some other anomoly.

Looking up a FQDN (Fully Qualified Domain Name) should return an A record (IP address). The verification step further returns the PTR record (if any) associated with the A record. Conversely, looking up an IP address should return a PTR record (if any), and if the PTR record exists, the verification step further returns the A record (IP address) associated with the PTR.

Note that PTR records do not necessarily exist, and if they do, there is no requirement for a one-to-one correspondence with A records. Furthermore, there is a common technique for reverse delegation called "RFC 2317 classless delegation," in which the query answer includes both a CNAME as well as the desired PTR record. Unfortunately, the local Resolver may return only the CNAME. In this case, the CNAME is displayed in the verification field, and "RFC 2317 reverse delegation" is displayed in the status area of Lookup window. To get the complete answer including the PTR, one must resort to the Name Server Query tool.

The Elapsed field shows the time in seconds that elapsed during the look up excluding the verification step. This can be useful for comparing the relative performance of different name server configurations.

The local DNR keeps a cache of recently requested items to improve system performance. The "Flush Cache" button issues a "dscacheutil -flushcache" command (or "lookupd -flushcache" on 10.4 or earlier) to empty the cache forcing the local DNR to request new information.

### Additional Features

When you invoke one window from another, the corresponding data is automatically transferred so you don't need to re-enter it.

A popup menu keeps a list of Recent Targets or history. The contents of the target field are added to the list when a test to that target is invoked. If the recent targets menu becomes full (10 entries), the least recently used item will be removed. To add or remove an item, or clear the entire list, use the corresponding selections from the History menu.

IPNetMonitorX recognizes the 'GURL' AppleEvent to handle URLs of the form:

    	lookup://www.sustworks.com

You can select File->Save to save a double-clickable ".ipnm" document with the corresponding URL. You can preview the URL that will be saved by pausing over the "Save" button in the panel that appears. URLs are saved as plain text. You can include multiple URLs in the same file, one per line, to open the corresponding tools.

You can open and use multiple Lookup windows at the same time.

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