I’ll use the Windows version, but the Linux version is very similar. First try this in a real computer then continue with a Packet Tracer lab. This is nslookup, which has an interactive mode also. There’s a command line utility with the same name in Windows and Linux too, which can be used to test and query the DNS. In IPv6 this is the AAAA record, but the purpose is the same. The A record gives the address pair of a domain name.

The MX (Mail eXchanger) record tells the name of the mail server of the domain. The NS record gives the name of the primary DNS server of the zone. Zone files start with the SOA (Start of Authority) record, which contains the parameters of the zone: the primary name server, the email of the administrator, the serial number to track the modifications and the timing parameters for the synchronization of the other DNS servers (there are a minimum of two independent DNS servers for any given zone). Each server is responsible for a zone which is a part of the whole DNS tree. The DNS database consists of Resource Records or RRs, which are located in zone files on the servers. But when a query is successfully answered, DNS servers can cache the data so that next time they can answer directly to the client. A root server won’t know the answer to the query about a particular address or name, it’s just relays the query towards a more authoritative server. The so-called authoritative servers know the exact information about a name/address correlation in a zone. These know the reachability information of the TLD servers, which in turn know the reachability of the SLD servers and so on. On the top of the hierarchy are 13 root servers (of course not individual machines, but server farms instead). The database behind the service is distributed among them throughout the world, just see. The ‘com’ is the so called TLD (top-level domain) part of the name, ‘yahoo’ is the second-level domain (SLD) and ‘The names are hierarchical, and so are the DNS servers. For example, the name is related to the IP address of 46.228.47.114. DNS is more complex than the following examples show, but these should be enough to understand the basics.ĭNS is a simple directory service it provides IP addresses related to domain names and vice versa. In this article, we’ll see DNS in action and how to simulate the operation of real domain servers. Click here to download the Packet Tracer files for this lab

Cisco packet tracer labs answers