![]() ![]() They use multiple servers to serve the request as one server is generally not capable of handling all the requests. This is usually the case with large organizations. Below we can see all the IP addresses associated with. ![]() This basically means that our DNS server queried an external DNS server to fetch the IP address. ![]() We can also set the current DNS server by using the command “server Ip-address”Ĭ) The third line in the output shows “Non-authoritative answer”. This is because DNS uses UDP port 53 to serve its requests. In this case, it is 10.0.1.1 and the port no is 53. This server is basically the current DNS server that will be serving our request. We will look more into records in the next section.ī) As soon as we type in we get an output showing the server and an IP-address#port. This means that we are querying for the A records which will return us an IP address in return for the domain we query. Just type in the commands as shown in the figure below.Ī) In the second line we set the type = a. We are going to use the “nslookup” utility for this demo. As soon as it finds the IP address it returns the IP address back to the user and also caches it for its future use. If it still can’t find the IP Address then it goes through a process or recursive DNS query in which it queries different nameservers to get the IP address of the domain. A DNS server is usually given to you by the ISP or you can manually set up a DNS server for yourself. If it can’t find the IP address in its cache it queries the DNS server to see if it has a record for it. A cache usually contains a mapping of IP addresses to hostnames which are saved during recent lookups so that the resolver does not have to fetch the IP address again and again. It first checks its local cache to see if it can find a record for the queried domain name. It is now the responsibility of the DNS resolver in the user’s operating system to fetch the IP address. Let’s say the user opens up the browser and types in. So Let’s understand how DNS resolution works. We will look more into Resource Records and the zone file in the next section. These records can provide us a bunch of information about the domain. A zone file is a file on the server that contains entries for different Resource Records (RR). This process may take place through a local cache or through a zone file that is present on the server. ![]() This is because domain names are much easier to remember than IP addresses. DNS converts human-readable domain names into IP addresses. ![]()
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