Dns file mx

If another team gets added then you create another paper list for teamD. So now you have three lists but who manages the lists? Well each team has a manager so you let the manager handle the list for the team. Now the league organiser Bill wants the phone number of Steve who plays for TeamA. How does he get it? So Bill needs a list with the name and phone numbers of all the managers..

So if someone wants to find the phone number of Steve on team A they contact Bill who returns the phone number of the manager of Team A John. They then contact John for the phone number of steve. As shown in the diagram below: If you compare this to IP addresses and Domain names. See Understanding DNS lookups.

Well all they need to do is to photocopy their list and give it to someone else Barry for example , and tell Bill the Contact number of the person so Bill can update his list. We also need to add a note in Johns list to include Barry as he needs to send him the list and list updates. Note: Primary zones are now called master zones and secondary zones are now called slave zones. To keep things simple only john can update the list. He has the master copy primary zone. When he changes the list he neds to send a copy to Barry who has a copy secondary zones or slave zones.

On DNS these changes are copied to the secondary zones in a process called zone transfer. Zone transfer is normally from primary to secondary, but it is requested by the DNS server responsible for the secondary zone. However the primary servers can be configured to notify secondary servers of changes. A DNS server hosting a primary zone is normally called a primary name server master ,and one hosting a secondary zone is a secondary name server slave. A DNS server can store and manage multiple zone files , and they can be a mixture of primary and secondary zones.

Primary and secondary name servers are both considered as authoritative for a domain. DNS Zones provide a very easy and simple method of grouping domain data from multiple domains together for storage. For domains to share a zone and hence a zone file the domains must be contiguous. A domain administrator would be responsible for creating zones, and delegating responsibility for these zones to an administrator and DNS server.

To illustrate we will refer to the diagram below which shows a section of the domain name system which has been divided into 3 zones. You should note that you cannot create a zone that includes Domain1 sub domain 1 and Domain 3 because they are not contiguous.

A zone file is a text based file with a format defined in RFC and and is stored on a DNS server name server. Referring to the diagram above the DNS server responsible for zone 1 will contain records that tell it:. The DNS server responsible for Domain 1 -sub domain 1 and 2 — i. Zone 2 has no knowledge of who has data for domain3 sub domain1 — i. The SOA start of authority must be present in a zone file, and defines the domain global values mainly to do with zone transfer.

When an administrator of a domain decides to allocate responsibility of a child domain to someone else e. This means that the zone file is stored on another DNS server than the parent domain. However the parent domain will keep track on the location of the zone by creating glue records to the name servers responsible for the zone data.

Caching is the process of temporarily storing data and is used frequently in networking, and on the Internet. DNS server and hosts cache DNS lookup data which means that they may be able to quickly resolve a lookup if it is already stored in the cache. The problem with caching data is what happens if the data changes, but the cache is still holding the old data?

Reverse mapping is not mandatory but is used frequently by applications like email to prevent spamming. Most DNS admin tools will automatically create the reverse mapping entry when you create the host entry.

John will need to find information for other players in other teams and he will use Bill to do this. What does this mean…..

It means you start at the. So you go from your current level straight to the top and then come down. Does that make sense? Rgds Steve. Hi Steve, I am using dns. Lucky to find your site while i was searching out for DNS information and explanation in depth. Thanks in advance. MX records are often modified to utilize a different email service than your hosting provider and designate personal servers as mail backups if the default mail option fails.

When using our nameservers, your default MX record is your domain name which contains a local IP address to the server, so all mail is handled locally. However, this record can be modified to point to a third-party email host, or you can add additional MX records and set their priority.

Important: These instructions are only applicable if you did not purchase Google Workspace through your hosting account. If you purchased Google Workspace through us, your email would be configured automatically. Make sure that your MX records are pointing to your hosting account. X example. It is better to include the essential parts of the link into your answer. The link could be outdated in the future.

Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Let's now see another example of zone file, with MX record. Our MX records for the domain example. So we now have two mail servers that will be responsible for receiving mails for the domain example. However mail2.

Hence we do not have an A record for mail2 inside our zone file. If our second MX record was something like mail2.

In the above shown example, mail. This means all SMTP servers sending mail to our example. Lower preference number means high priority, and higher preference number means lower priority.

The most important thing to remember about the MX record preference number is that Preference number can have any value between 0 to Pick any book about DNS, and you will see the values in multiples of Why is this convention followed? The primary reason for having the higher priority mail server with a priority of 10 is because, at a later point, you can add another server inside your DNS zone file with a value lower than 10 like 8, 9 or anything.

This enables you to modify your high priority mail server yet again, if something happens to the earlier one. All this can be done without touching any other MX record. Means simply go and add another MX record with a new mail server with preference number of 9 leave other records untouched.

This is the only reasonable argument, for the convention of having MX record priority numbers starting from We did see that lower priority number means higher preference.

Now what if two MX records have the same priority number of In that case, both are given the same preference, but it will depend on the client SMTP server. An example of such a zone file is shown below. Another technique that you can do with DNS to load balance your mail server is to have multiple servers with different IP addresses, accepting mails for the domain.

Say for example, you have two mail servers In the above shown example, we have only one MX record with the preference number of But we have two physical servers, which both will resolve to mail.

We saw that the SMTP server will try the second priority mail server reported by MX record for the receivers domain , if connection to the primary was not successful.

However this entirely depends upon the SMTP server the sender is using. For example, some SMTP servers will try the lower priority MX record, only when the higher priority mail server is not reachable at all.