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Posts tagged as “PTR record”

5 DNS records you should know

By Bob on March 5, 2022

What are the DNS records?

DNS records are text-based instruction for name servers (DNS servers) that can serve to link hosts to IP addresses, IP addresses back to hosts, services to hosts, one name of a host to another, combine to have complex rules, and more. 

There are some DNS records that are quite essential for the DNS functionally. Here are the first you should learn.  

The 5 DNS records you should know are:

A record

A record is the first that you think about when you are talking about DNS. It links domain name / hostnames to their IP addresses. When somebody wants to visit a site, they usually know its name (domain name). But what they actually need to find it is its address. The visitor’s browser will go on a long search, from one DNS server to another, until it gets the A record that resolves the query. It gets it back, and the browser knows already where the site is and can load it. 

SOA record

This is the start of authority record, which indicates the primary DNS server – the authoritative name server. It also contains information about the DNS zone, and it is a must-have for the normal functionality of your DNS network. Inside it, you can find out which is exactly the authoritative server, who is responsible for it, how often should the DNS server refresh, and more. 

PTR record

It is a bit neglected DNS record, but it is a must-have if you want to send emails without problems. The PTR is a pointer record that has a functionality opposite to the A record, and it serves for Reverse DNS. It can point an IP address to a domain name. Why do you need it if people don’t remember IP addresses? For the machines! Because when you send an email, the receiver will want to check if this email was really sent on behalf of the domain it is saying or no. If the A record and the PTR record are not configured properly, the emails will go to spam. It can work both with IPv4 addresses and A records or with IPv6 addresses and AAAA records. 

Why do you need a PTR record?

CNAME record

The CNAME record is used to show which is the real domain name (canonical) for domain / subdomain that you are looking for. You should know this DNS record because you should use it for all your subdomains. That way, you can just create CNAME record for them and point to the domain name without the need to create more DNS records for them. When you update DNS records for the YOURDOMAIN.com, you won’t need to update subdomain1.YOURDOMAIN.com, subdomain2.YOURDOMAIN.com, and so on. It will facilitate DNS management for you. 

MX record

This record is also important for email correspondence. It is known as the mail eXchanger record. It will show which exactly is the server or servers that are responsible for accepting emails for the domain. As you can most probably guess, without this DNS record, the sending servers won’t know to who they should send messages, and you can’t receive emails. So, with the PTR, you were fixing the sending, and with the MX record, you are fixing the receiving part. 

Conclusion

This is a good first step into the world of DNS. There are plenty of DNS records more, but now you know how the most important of them look like. The A, SOA, PTR, CNAME, MX are among the first that you should know and start using right away. 

rDNS (Reverse DNS) explained

By Bob on March 24, 2021

So you have set up your Forward DNS. You are happy that you added all the needed DNS records, and you think you are done. Guess again! What are you missing? Just try to send an email from the domain, and immediately you will notice a problem. Your emails are going missing or to the SPAM folder because you haven’t set up a rDNS (Reverse DNS)! Luckily, now you will learn all about it.

What does rDNS mean?

The Reverse DNS is a service, a part of your typical managed DNS plan, and it allows reverse lookups. It lets you create a Reverse DNS zone, where you can add PTR records and use them as proof that the IP addresses and the domain name matches.

The Reverse DNS works with both IPv4 addresses and IPv6 addresses. You can use it with one or the other or both at the same time.

You will need proof that the PTR records provide so servers of other companies can backtrack the IP address to the domain name, and that way, to be sure that it is not a scam.

You will need the combination of A (IPv4), or AAAA (IPv6) records that map domain names and IP addresses and PTR records that have the opposite purpose, IP addresses to a domain name.

Why should we care about rDNS?

You should care about rDNS if:

  • You want your emails to arrive at their destination and check of the incoming mail server to finish successfully. You will most probably need a few more records than the PTR, like SPF, DMARC, and DKIM records.
  • If you are an IP network owner, you will need it to be able to do reverse lookups.

How to start using Reverse DNS?

  1. Get a DNS plan with Reverse DNS. The rDNS is a service that is usually missing from the free DNS plans. So, first, you will need to get a paid plan with Reverse DNS included and other parameters that you will need for your Forward DNS.
  1. Create a Primary Forward DNS zone. You will need to add the A or AAAA record that links your domain name to the IP addresses first.
  2. Create a Primary Reverse DNS zone. You can do it from the control panel of your provider. There you find the add Reverse DNS zone. Pay attention to the instruction. Usually, you will need to add a range of IP addresses in reverse.
  3. Add the PTR records. They must link the IP addresses to A or AAAA records in the Froward DNS zone. If they don’t make a match, it won’t function.

Can you check your Reverse DNS?

Yes, you can check your Reverse DNS by probing the IP addresses and see if they lead to the hostname. The easiest way to do it on most of the OSes (Linux, macOS, Windows, etc.) is to use the Nslookup command:

nslookup 192.169.1.2

Just change the IP address, in this case, is 192.169.1.2, with the one you want to verify. This one is an IPv4 address, but you can put an IPv6 address too.

If you need more information I recommend you this article: What is Reverse DNS?

Conclusion:

The Reverse DNS is a must-have when we are talking about sending emails. If you don’t set it up correctly, you might have emails that don’t arrive at the destination. That can cause missing opportunities, problems, and extra costs. You don’t want to lose money just because you didn’t set up your rDNS, do you?