Zone files dns

In out analogy John could have a copy of TeamB list in case Fred goes on holiday. Therefore a DNS server can be both a primary and secondary name server. Zone File Storage In our analogy the data is stored on a paper list and kept by the team manager. Zone files contain the IP and name data, MX records and other service records. They also contain glue data that connects them to the other DNS servers. Which DNS servers have data for Domain3 sub domain1 i..

List of Root servers root hints List of forwarding servers if using forwarding The DNS server responsible for Domain 1 -sub domain 1 and 2 — i. An example record is shown below. Zone Delegation When an administrator of a domain decides to allocate responsibility of a child domain to someone else e. We saw this with Bill Needing to know who had the list for Teams A.

Caching and TTL Caching is the process of temporarily storing data and is used frequently in networking, and on the Internet. In our example above when someone requested the phone number of Steve, Bill remembers that information for a short time in case someone else needs to know it. Please rate? And use Comments to let me know more. HI, There is an error in your WordPress configuration and website is showing error.

Please fix. Hi Tks for pointing that out. Hi Sorry but not familiar with it. Hi Steve, Lucky to find your site while i was searching out for DNS information and explanation in depth. Regard, Vivek. As shown in the diagram below: Regarding john traversing back. Thanks for clarifying — Had couple more questions. Luckily I got your article when I was searching for the explanation …….

Please keep going ……… Regards, Swaminathan Shanmugam. I wanna talk wrt browser point of view. Hello Steve, Thanks for such an easy and understandable explanation.

Hi Steve, It is really great work, thanks a lot! Best regards, Phil. Hi Steve, It was a great explanation and analogy made to understand the concept in a simple way. Thanks, Rithin. Leave a Reply Cancel reply Your email address will not be published. Leave this field empty. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits.

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For example, our local name server only provided the FQDN Fully Qualified Domain name of the 13 root servers in the initaial phase of the trace, according to the output.

Using trace option with dig by default suppresses the additional part. Let's now get back to our topic of zone file. Let's once again take the above example of example. As shown in the trace output, example. Now that zone file will contain the entire details for that domain.

We will see the contents of a zone file and understand the meaning of the content in some time. This file contains the complete details of all resource records for that domain.

In other words it will contains the entire ip to domain mapping of the domain. Zone files are made in such a way that it can be made portable for any DNS server.

The main purpose of this tutorial is to understand the contents of a zone file, and how they play a major role in the DNS system we will also be studying some of the widely used resource records in DNS. We will be discussing bind related configurations in a separate post, as it requires special attention. In the above image, i have tried to depict an example configuration of DNS zone file for the domain example.

Let's understand each and every part of that zone file separately. In the above shown example configuration file, there a TTL value assigned by the below method. TTL stands for Time To Live, which mentions the time in seconds for which caching name servers can cache the data. Here the TTL value mentioned in the beginning of the file, is the bind's method of specifying the default TTL value for the domain, if not explicitly mentioned. Let's take an example to understand TTL. I will do a simple dig against google.

In the above example, the TTL value of mentioned in the second column of the output is the number of seconds remaining for the TTL to expire. Please note the fact that, the above reply is given by your local name server which you have in your resolv. So if you repeatedly do a dig for google.

So let's find out the exact TTL value for Google. So you will always get the TTL value of , when you do a dig by using ns1. There are two things that you need to consider about TTL value. Which means the servers which gives you the address of authoritative name server for a domain, has a higher value TTL.

The default value of that TTL most of the times is 48 hours 2 days. That large value is correct, because its very less often that people change the authoritative name server IP addresses note the fact that the above output is the data given by a. SOA is the mandatory record that must be there in all zone files. It specifies the main properties and characteristics of a domain.

We will walk through each of them one by one. The default format of specifying a SOA record is shown below. NAME: This specifies the name of the domain. As mentioned before, i am using a zone file made for bind DNS server.

If you see our SOA begins with the following line. IN SOA ns1. Using at this place will replace it with example. So www. The final DOT specifies the root name servers. RR : This specifies the resource record name. Please note the fact that there must be a A record for this name server later in the same zone file that will specify the IP address of that name server.

We will be discussing A records in some time. But if you see our example zone file, you will see that its admin. That's simiply because sign in zone file has some different meaning other than email address. Serial number tells the modification date of the zone file. Every time you modify the zone file, you also need to modify the serial number. Serial numbers in zone file follows a date format of yyyymmddss. Which means if you have edited your zone file on 12th September , your serial number will be This entry of serial number is mostly used for zone transfer to confirm the last modification of the zone.

We will be discussing the zone transfer stuff in a dedicated post. EXPIRY: This specifies the duration after which the slave name server will stop responding to DNS queries if the connection to master server cannot be established by following retry interval. If you see the above dig command, i have used a domain name that does not exist. So the name server for google. Hence our final zone file SOA record will look something like below, which was also previously shown in the image.

And what kind of records can be used in a DNS zone file? First, we must specify the data portion of this record. In the case of an A record, this would be the name of the subdomain. Then we have to set a TTL, for example, In some cases, for the MX records, for example, we can have additional fields like Priority between the DNS type and the host. Below, we have an example of a DNS zone file from a cPanel server. For this case, the important data like real domain names and IPs have been replaced.

What is the DNS Zone management? This kind of management includes different tasks related to the DNS zone file, like editing DNS records, adding new records and deleting existing records. A proper management of the DNS zone is important to keep it working.