DNS Lookup

Gentle Giant

Giant Admin for a Day
Staff member
Free online network utilities, from Central Ops net. http://centralops.net/co/

Cool things you can do:

AnalyzePath - Do a simple, graphical traceroute.
AutoWhois - Get Whois records automatically for domains worldwide.
Browser Mirror - See what your browser reveals.
Domain Check - See if a domain is available.
Domain Dossier - Investigate domains and IP addresses. Get registrant information, DNS records, and more.
Email Dossier - Validate and investigate email addresses.
NsLookup - Look up various domain resource records with this version of the classic NsLookup utility.
Ping - See if a host is reachable.
Traceroute - Trace the network path from this server to another.
TcpQuery - Grab a web page, look up a domain, and more.
One for the techies, & very useful for the rest of us.

It's free, very simple to use, & can be added to your browser's search-bar (definitely in Firefox, maybe in Internet Explorer).
You can go into great detail with this tool, or just get the simple stuff we mostly use in AFI.

Brief intro from the home-page. (It uses your IP as a clickable example)
swiss army knife internet tool
in the searchbox above you can search for:
RBL checks multible RBL:s if a specific is listed (YourIP)
DNS checks detailed dns information for a hostname (Yourhostname) or a domain (YourISPdomain)
IP-number checks ip number information such as dns reverse and forwards (YourIP)
C-net checks an entire c-network (yourCnet)
whois lookup checks whois information for a domain (YourISPdomain)
route checks a specific routed prefix ()
AS numbers checks information on an AS-number (AS ())
BGP announcements checks prefixes origined from a specific AS-number (AS)
AS macros checks who belongs to an AS-macro (example: as-ams-ix-peers)
RFC documents Request For Comments (rfc2822)
add engine to browser

A good tool, I use it a lot.
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IP Tracing

Its all good to trace IP addresses however keep in mind they can be faked or just rerouted, it all depends how good in computers someone is to establish and use proxies, mirror site and tunneling etc, by itself the IP locator can only provide an indication
WorldIP 2.02 Firefox add-on

These tools, which include an add-on for Firefox, give lot's more data about the site you're looking at, accurate location, ping, trace, reverse DNS, all from the context-menu, or an icon on the status-bar, & more on the main site.
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Sorry to post on old thread but IP and domain trace are kinda right in my field of spam fighting. Here is couple with short explanations.

This covers ARIN, APNIC, LACNIC, RIPE and AFRINIC databases in .aero, .arpa, .asia, .biz, .cat, .com, .coop, .edu, .info, .int, .jobs, .mobi, .museum, .name, .net, .org, .pro, and .travel domains.
InterNIC is basically common peoples interface to communicate with ICANN (the nets big boss) see also home http://www.internic.net/index.html and find own way to use it.

Jørgen Mash's DNS database list
Can trace IP or domain and uses huge database of blacklists ie. wide results.
Slightly confusing results and needs fair ammount of users judgement.

Several easy tools to trace IP and a cesipher to process email headers with option to send abuses.

Cisco IronPort SenderBase Security Network
Gives a good report to judge how reliable is an IP when talking about email source.
Needs users judgement and little bit of knowledge obtained by experience.
(IronPort is behind of easy and popular spam reporting service Spamcop.net
Please register an accout there and post any abusive mail in.)

Enter an address, netblock or hostname you wish to check.
Again more focused on spam but might be useful to spot a bad source.

The AHBL is a database of hosts that have been known to cause various forms of abuse on the Internet which includes UCE/UBE/spam, Denial Of Service attacks, cracking attempts, and much more.

This is not a real lookup service like others but they are recognized by New Scotland Yard, FBI and other major LE.
Focused in spam again but if you find IP here its propably really bad one.