Top Mud Sites Forum - View Single Post

Pymeus · 01-11-2015, 05:45 PM

Almost certainly -- that's what rDNS is for, and I'm not aware of any other remotely reliable way to do it.

Speaking of reliable, you can't trust an rDNS entry by itself. It can be anything, including invalid and non-resolvable junk. Mail servers see spammers with spoofed "gmail.com" rDNS entries with extreme frequency. A good implementation will do the rDNS lookup ("gmail.com"), and then confirm the answer by looking up the returned hostname (if any) and comparing the returned IP address(es) to the IP we're trying to find out about.

I don't know as much about whois from a technical standpoint. I know it's a separate (though related) system from DNS, and I'm pretty sure that it's much more centralized than DNS. Most or all whois servers are aggressively rate-limited and forbid you from using them for automated lookups, making them a poor choice for learning about IPs on a large scale.

01-11-2015, 05:45 PM	#5
Pymeus Member Join Date: Oct 2008 Home MUD: tharel.net Posts: 36	Re: Resolving IP addresses Almost certainly -- that's what rDNS is for, and I'm not aware of any other remotely reliable way to do it. Speaking of reliable, you can't trust an rDNS entry by itself. It can be anything, including invalid and non-resolvable junk. Mail servers see spammers with spoofed "gmail.com" rDNS entries with extreme frequency. A good implementation will do the rDNS lookup ("gmail.com"), and then confirm the answer by looking up the returned hostname (if any) and comparing the returned IP address(es) to the IP we're trying to find out about. I don't know as much about whois from a technical standpoint. I know it's a separate (though related) system from DNS, and I'm pretty sure that it's much more centralized than DNS. Most or all whois servers are aggressively rate-limited and forbid you from using them for automated lookups, making them a poor choice for learning about IPs on a large scale.