Reviews Best says:

There are a couple of ways to do this. Open a DOS COMMAND window. In the window at the prompt type:
tracert domain.name
where domain.name is YOUR domain name. What you will get back in return what the DNS thinks is YOUR IP address for your domain and the IP address and domain for every hop between you and your domain. Trace route is better than PING because it returns MORE information. Not only will your hosting IP be there as the last entry, but the entry just before MIGHT be the host name and IP who is the reseller serving YOUR host. As a matter of fact, there could be a daisy chain of several resellers. The next thing to do is take your list and start tracking back entry by entry to see who is what. Any domain registrar site has a “whois” function where you type in the domain name or an IP address and they tell you the information regarding the domain, when it was registered, when it next expires, who various contacts are, and the like.
Here is what is returned by tracert in a command window. I am tracing the route from ME to GRAMBLER.NET, a domain I already KNOW is hosted by a reseller. Note the 1st entry of 192.168.0.1. That is MY router in my DSL appliance. The 2nd entry is my ISP, Avvanta. I replaced my actual IP address assigned by Avvanta with X’s. You have NO need to know my actual IP nor does anyone else. No need to encourage hackers from trying to get into MY system from outside.
-=+=-
Tracing route to grambler.com [207.45.185.138]
over a maximum of 30 hops:
1 1 ms <10 ms 1 ms 192.168.0.1
2 70 ms 56 ms 57 ms v-static-145-254.avvanta.com [206.124.xxx.xxx]
3 59 ms 56 ms 160 ms core-01-ge-0-2.sttl.isomedia.com [207.115.64.163]
4 62 ms 56 ms 57 ms bord-05-ge-0-0.sttl.isomedia.com [207.115.64.135]
5 54 ms 55 ms 57 ms ge-6-23.car4.Seattle1.Level3.net [4.71.156.117]
6 70 ms 66 ms 72 ms ae-32-52.ebr2.Seattle1.Level3.net [4.68.105.62]
7 181 ms 75 ms 78 ms ae-2.ebr2.Denver1.Level3.net [4.69.132.54]
8 108 ms 102 ms 117 ms ae-3.ebr1.Chicago2.Level3.net [4.69.132.62]
9 120 ms 72 ms 102 ms ae-6.ebr1.Chicago1.Level3.net [4.69.140.189]
10 119 ms 107 ms 107 ms ae-1-100.ebr2.Chicago1.Level3.net [4.69.132.42]
11 148 ms 128 ms 115 ms ae-8-8.car1.Detroit1.Level3.net [4.69.133.241]
12 117 ms 190 ms 107 ms ae-11-11.car2.Detroit1.Level3.net [4.69.133.246]
13 110 ms 115 ms 115 ms 4.53.74.58
14 114 ms 122 ms 110 ms core1.acenet-inc.net [207.45.176.2]
15 234 ms 170 ms 166 ms grambler.com [207.45.185.138]
Trace complete.
-=+=-
So next, go to http://samspade.org and put a domain name in the WHOIS box. On the next screen will be the host information. Next click on the IP address at the top of the data and that will take a step back to THAT IP address and domain. By clicking on the IP address and then the name and then the IP again and then the name, you can trace backwards through the hosting chain. It is kind of hard to explain how the back tracking of IP addresses works at samspade dot org by clicking first the IP then the domain then the IP but I am sure you can figure out what to do. If one or more of these IS a reseller, there is NOTHING that is proof positive that ANY of the entries points to a reseller.

mti2935 says:

Yes. Ping your own web site, and that will show you the IP address of the web server that is hosting your site. Then, do a WhoIS lookup on that IP address, and that will show you who owns the IP. A reverse-DNS lookup on the IP may show you some useful information as well.