Domain cname what is

Another common use is for the www subdomain. Having purchased example. It is worth noting here that example. One option would be to set up another A record, pointing to the same IP address as for example. This is completely valid, and is what the real example. What happens if you need to update the IP address that example. You would also need to update it for the www subdomain, and any others you may use. At the time when the DNS standards were written, some rules were set out to govern their use.

It is possible to use a CNAME at the root, but it can result in unexpected errors, as it is breaking the expected contract of behavior. An example of this is told by Cloudflare , describing problems they encountered with Microsoft Exchange mail servers after having used a CNAME on their root domain:. Here you see the downside that can appear in several server softwares or libraries.

Because a standard is in place for a CNAME to be the only record at a node, no other records are looked for. All other records will be silently ignored, without warning or error messages. So why is this a problem? Surely that is the end of the path when looking for the IP address of the web server hosting your content?

In the modern internet landscape, that is no longer the case. The world is very different from when the DNS standards were written. You may choose to use a Platform as a Service PaaS provider like Heroku and store content on their web servers.

You control the content, but not the infrastructure, and the PaaS provider does the heavy lifting of the network maintenance. They typically provide you with a URL my-app. The scale and frequency of backend changes made by the PaaS provider can make it hard to maintain your root domain A record pointing at a single IP address.

Ideally you would wish to do this:. However, as we now know, this breaks the DNS specification, so is a very bad idea. However, that instruction takes place either on the web server so still having the problem of needing to use a fixed A record in DNS to point to that web server , or a custom DNS provider redirect that suffers complications with HTTPS. This also has the side effect of changing the domain that you see in the URL bar, which you may not want.

Several DNS providers have now developed custom solutions to work around this problem, including:. The exact implementation can differ, but at a high level when the DNS server sees one of these virtual record types, it acts as a DNS resolver.

It follows the chain created by the alias until it resolves at an A record or records and returns these A records to the DNS server. These virtual records can sit alongside other records at the root without any fear of unintended behaviours.

They can also be utilized to point a group of company websites to a parent site, or to have the same domain registered in multiple countries, but with each version pointing to the same place. As they say, a picture is worth a thousand words. Each of these examples will eventually resolve to the IP address configured in the A record for your domain.

One last thing to keep in mind is that CNAME records essentially result in having two queries for one lookup, as a nameserver that finds a CNAME record needs to look for the record that points to the main destination. There are several online tools that can do this such as:. You can also use these tools to perform lookups for other records configured for your domain. Multi-CDN Management. Compare Outages Outage Prevention. August 28, Give us your email and we'll send you the good stuff.

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