 Hello, DDS Davens here, continuing my series of videos, short videos on my tool DNS resolver. So let's look at the man page, at the different commands that my DNS resolver tool implements. We're going to start with a simple command, wildcard. It's not the first command that I implemented, but it's a simple one to start with. And here you have the explanation for wildcard command in the man page. So the type is wildcard, the label is mandatory, that's how we are going to recognize a query for a wildcard command. It has to be a valid DNS label and then you have optional logging. So let me start DNS resolver with such a command, type is wildcard and label let's say wc. And as you can see now, my DNS listener resolver is running UDP port 53 on all interfaces here on my machine. And here, if I do an NS lookup for let's say example.com, point it to my own machine here, localhost, you get an answer, non-existing domain. Because my DNS resolver is not resolving, is not sending requests to another server. If it cannot resolve itself, then it ends with NX domain, domain is not known. So here you can see that NS lookup is sending A and AA records. And now we will look into that in more detail later. But let's just try directly a wildcard command. So one, two, three, four, wc like this. And then I get as answer one, two, three, four. So I can encode the IPv4 address that I want into my domain name here. So wc at the fifth position, that is the label that identifies this as a wildcard command. That's how my DNS resolver knows, okay, now I need to do the wildcard command. And then the four digits separated by a dot and before the wc label that is interpreted as an IPv4 address and that is then returned. I can, for example, also return localhost like this and then I get this answer. So it's as simple as that. Now coming back here to the different records, so you have A and AA. That's something we can instruct NS lookup to do. For example, let's say type A, only type A. And now there are no more AA queries. Let's try another domain, test.com or text.com here. And here now you can see it appended LAN and got an answer. That is how my DNS client is working here. If I really want text.com and nothing else, I can put the root, dot here, the root server and then I get here a query text.com, the only query. Let's stop the server and add logging like this, wildcard log. Let's call it like that. And let's do another query like this. We got the answer. And now here a file has been created that starts with wildcard-log and then a timestamp when it was started. And that log file contains the query. And then here you have a line per query with a timestamp from where it came. And then the full DNS name here.