Migrating DNS to M.D.G. IT Print

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See also: DNS in summary and in detail

How moving DNS works

When pointing a domain at new nameservers, both old and new nameservers should have identical records. The purpose of this is to avoid the long propagation times involved when updating to new nameservers with different records, during which visitors can be taken to either the old or new service, depending on whether DNS has propagated to their network.

When the nameservers are then updated at the domain registrar, the change is completely transparent, and doesn't cause any changes to where the website and email are hosted. Changes to DNS are then made on the new nameservers, and take effect within minutes.

The steps to moving DNS to M.D.G. IT are straightforward:
  1. Duplication of the existing zone file to M.D.G. IT nameservers
  2. Updating the domain at the domain registrar to point to these new nameservers
Step one is, however, complicated by the fact that it is not possible to know all the DNS records that exist for a domain. When duplicating DNS we can look up the main and the www A record, which define where the website is hosted, as well as the MX records, which define where mail for the domain is sent, however we cannot know the existance of arbitrary records. This is because most DNS servers will refuse a request for all of the records for a particular domain, and only return specific queries.

In practice this means that there is no way of knowing if, for example, blog.yourdomain.com exists in DNS, and hence needs to be added to the domain's records on the M.D.G. IT nameserver, without either being informed of its existence, or having acccess to the existing 3rd party DNS provider account.

What we need

For this reason, when transferring DNS to M.D.G. IT, we ask for one of the following:
  • Access to the remote DNS host's control panel, so that we can look at the complete zone file for the domain, and see every record that needs to be created on the new nameservers. If DNS is hosted with the previous webhost, and we are migrating the site from this host, we would normally have access to this already; or
  • A copy of the zone file for the domain, which lists every record. This can be provided by the previous host / DNS service provider; or
  • A list of all subdomains that need to be set up, or confirmation that no records other than the main domain, www and MX records need to be created.

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