DNS.COMPUTER/blog

How to use Linux MTR command?

April 5, 2021July 20, 2021 Martin Pramatarov No Comments

Commands

There are plenty of programs for network diagnostic. You might wonder, do we need one more?

If you want to trace the route of a query, yes! The MTR command could slightly outperform the traditional Traceroute command and give some more data, so it has a reason to exist.

What is MTR command?

MTR comes from Matt’s traceroute. First written by Matt Kimball in 1997 and later updated with Roger Wolff’s help, this is software with CLI that helps you see the route of a query.

It is based on the traditional traceroute command, but it presents each of the hops on the way, with a table-like view and data like data loss, amount of packets sent, the time of the return of each hop.

MTR command syntax

How to use Linux MTR command?

NSlookup command – what is it?

September 16, 2021September 16, 2021 admin No Comments

Commands

What is the NSlookup command? The NSlookup command is still a popular tool with a command-line interface for DNS probing. You can use Nslookup commands for checking the domain name, its IP address, or different types of DNS records. It has been around for a long time as a part of the BIND software. It … Read More “NSlookup command – what is it?” »

What is a DNS flood?

August 10, 2021August 10, 2021 admin No Comments

DNS

Cyber attacks use different techniques to harm their targets. Depending on how strong the target’s defenses are, the power of the attack. Today we will talk about DNS flood, considered in the category of the dangerous DDoS attacks. Understanding how it works can be a good way to know how to defend against it. What … Read More “What is a DNS flood?” »

What is the Traceroute command, and how to use it?

July 18, 2021July 20, 2021 Martin Pramatarov No Comments

Commands

The Traceroute command is a network tool that helps you see the complete route of a query and identify problematic spots on the networks, such as slow or not responsive routers. You can use it through the Terminal with a simple “traceroute + domain name” command.

It is light, fast, and does the job it was designed for. The great thing is that you can find it on the most popular OSes.

What is the Traceroute command?

The Traceroute command is a simple software with a CLI interface that serves to show you each hop of a query from your computer to the destination – IP address or domain name. It races the route of a probe and gives back the result.

The query will travel through the internet, hoping from a router to another and finally reaching the destination. At each of the hops, your computer will send packets and get answers for them. That way, you will get statistics about each of the points, from your device to the destination.

Syntax of the Traceroute command

What is Reverse DNS?

July 14, 2021July 20, 2021 Martin Pramatarov No Comments

DNS

A Reverse DNS is usually a premium feature inside a paid managed DNS plan. It is a service that is mostly directed towards IP network owners and offers IP address to domain resolving. Other business owners might also be interested in it because that way, their emails have a better chance of not going to the spam folder.

Reverse DNS explained

Reverse DNS, also known as rDNS, does the opposite to a Forward DNS, which is to map IP addresses to hostnames. The purpose of the Reverse DNS is to provide a way to verify the IP addresses and confirm that they are related to a particular domain name. It is especially important when we are talking about the verification of mail servers or other services.

If you can’t verify, it is safer to mark it as dangerous, and this is what many servers could do if there is not Reverse DNS zone to be checked.

In short:

In Forward DNS, a domain name is pointing to an IP address where it is hosted.

In Revere DNS, An IP address is pointing to a domain name to verify it belongs to it.

How to start using Reverse DNS?

Why do we need to use a DNS TXT record?

July 7, 2021July 20, 2021 Martin Pramatarov No Comments

DNS, DNS records

Let’s explore one DNS record with multiple purposes – the DNS TXT record. It is used for various verification methods, and it is essential to the right mail server functionality.

What is a DNS TXT record?

The DNS TXT record is one DNS record type with multiple purposes like authentication, verification, mail policies, and more. The DNS TXT record is showing domain information to external sources.

The TXT record has a text field that can be filled with readable instructions for people or with instructions for computers like cryptographic keys and email instructions.

You can add multiple TXT records for the same DNS zone. They can have different purposes, and sometimes they can work together, like in the case of DMARC.

Ensure mail delivery with DNS SPF record

June 7, 2021July 20, 2021 Martin Pramatarov No Comments

DNS, DNS records

There is nothing more frustrating than not been able to send emails correctly. You want to reach to clients with new offers, contact suppliers for additional materials, inside the company communication, and all with problems! What you need is to fix all the issues and missing configurations. Ensure email delivery with DNS SPF record and a few more DNS record types.

What is the DNS SPF record?

Domain Name System Sender Policy Framework record, or DNS SPF record for short, is a DNS record that provides important information about a domain name that indicates the outgoing mail servers it has.

If the MX records show which email servers should handle incoming emails for a domain name, the SPF records show which email servers should send emails on behalf of a domain name.

When you send an email to another person, like, for example, John@site.com, the incoming mail servers of site.com will first check your domain name. They will be searching for the SPF record and follow the rules that it establishes. Only if the SPF record is present, then your email will be received without been discarded or put into the SPAM box.

NAPTR record explained

April 21, 2021July 20, 2021 Martin Pramatarov No Comments

DNS, DNS records

The NAPTR records are not as commonly used as A DNS records, but they have an important purpose: linking servers and users’ addresses in SIP.

What is the NAPTR record?

NAPTR DNS record is a Name Authority Pointer record. It is a type of DNS record that serves to map servers to the users’ addresses in the so-called Session Initiation Protocol or SIP for short. The NAPTR records, together with another type of DNS record called SRV records (service records), allow complex rewriting of rules that provide new uniform resource identifiers (URIs) or domain labels. Depending on the flag of the newly created URI or domain label, it could be used in the following query for a NAPTR record or directly as an output of the entire process for URI mapping.

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What is Round-Robin DNS?

April 13, 2021July 20, 2021 Martin Pramatarov No Comments

DNS

Round-Robin DNS is the simplest solution that you can apply to create a DNS load balancing for your domain. With Round Robin, you can manage the DNS traffic in a way that will utilize your authoritative name server and redirect the traffic, reducing the stress from a single point (direct to multiple web servers).

What is load balancing?

Load balancing is a method for optimizing the network performance by utilizing a particular algorithm to administrate the traffic between multiple servers. The traffic management criteria could be different – the IP address of the visitor, the current occupation of a server, weighted loading balance that depends on the servers’ capacities, and more.

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What is Master (Primary) DNS zone?

March 23, 2021July 20, 2021 Martin Pramatarov No Comments

DNS

What is a DNS zone?

The domain namespace in the Domain Name System (DNS) is divided into various segments, with different managers in charge. The administrative responsibility can be delegated to a person, company, or organization. This separation is good for redundancy and better distributes the administrative load.

The Internet’s domain namespace has a hierarchical design. Un is the root domain (the dot after .com), then is the domain name like domainname.com, and under it, there are subdomains like mail.domainname.com or ftp.domainname.com.

Each of these areas can be managed separately with its own Master DNS zone.

A DNS zone has inside DNS records and settings of a DNS namespace. This last one can have one or many DNS zones managed for a specific host or service. All this zone information is saved in a DNS zone file that has the DNS records.

Those records have a mapping between DNS names and their IP address, services and servers, verification purposes, and more.