This is a recurrent question from our customers: does the use of the DNS, whether it is good or bad, have an impact on the websites’ SEO? We have already discussed about the impact of a HTTPS website on the SEO, this is now the occasion to focus on the side of the DNS.

The DNS is an invisible process, implemented in the background, it’s difficult to comprehend why it can help or affect a website’s performance and the ranking in search engines, more particularly on Google.

This article will approach the possible impact of the DNS in response to the following questions:

• Does the modification of a DNS record affect the SEO?
• Does the change of the DNS provider affect the SEO?
• Which part of the DNS plays in a website’s migration?
• Does the change of a website’s IP address affect the website’s SEO?
• Quid of the DNSSEC implementation?
• Can a DNS breakdown affect the SEO?
• Can a faster DNS increase the SEO?

Does the change at the DNS level affect the SEO?

1. Modification of a DNS record, be careful of the TTL

The domain name’s redirection towards the corresponding web server often passes through the creation of a A type record (IPv4 address). The A record will then direct the traffic towards the IP address of the destination web server. The modification of this record can lead to performance problems.

Indeed, to optimize the response time, the DNS system allows the  information caching with the DNS resolver servers for a given time, the duration of the TTL (Time to live) defined by the technical manager of the domain name, during its configuration. The usual TTL, like the one recommended by ANSSI, is several hours for the usual uses of domain names (websites). In the case of a A record modification, this one could be taken into account only at the end of the TTL. Then web users could still access to the former record configurations for a few minutes or even several hours after the modifications.

Thus it’s important to reduce the TTL, even temporarily during these modifications.

But does that affect the SEO? Yes, it does and no, it doesn’t. In the case of users being sent towards a destination that no longer exists, Google will consider this as a 404 error. Beyond the negative user experience, this is not directly a SEO factor. However be careful of the possible existence of backlinks and the too high numbers of 404 errors. A low TTL allows to limit the impact during these modifications.

2. Modification of the DNS declared for a domain name

A domain name is associated to the name servers (NS/Name Servers) which allow the right DNS resolution. The DNS service searches the information on these NS. These NS can be modified during the change of the provider managing the domain name, or simply to pass from a DNS infrastructure to another. Will the change of the name server affect the SEO?

Depending on the provider and the chosen infrastructure, the resolution time could be more or less short with a possible impact of improvement or decrease regarding the SERP (Search Engine Result Page). Indeed, the resolution time is taken into account by Google (see after).

And like for a record change, it is recommended to reduce the lifespan of the records before modifying the name servers, so the DNS resolvers don’t keep in cache the former information.

3. Risk associated to the DNS during the website’s migration

This is the same principle discussed previously. The modifications of the DNS configurations don’t directly affect the SEO, but can lead to a bad user’s experience. The TTL should also be seen as a useful mean to take into consideration.

Which specific cases to consider?

• Change of web hosting provider
• Change of DNS hosting provider?
• Move the traffic of www. towards a “nude domain” (without www.)
• Move your domain towards a CDN (content diffusion network)

4. Change of the destination IP address

No. During the modification of a record pointing from a termination point to another, the SEO is not affected. The only (very rare) exception to this rule would be to point a domain towards a termination point that would have been already identified as a spam server (for example, the IP address of a shared server).

However, be careful of the IP address in question, one of the (many) rules of Google’s SEO is that an IP address used for a website should be located near the final user.

5. DNSSEC implementation

DNSSEC allows to authenticate the DNS resolution through a chain of trust between the different DNS servers of this resolution. Just like for the HTTPS, this is an additional security layer to implement. And like for the HTTPS, the pages’ loading time is affected, and therefore potentially the associated SEO. To put this into perspective, DNSSEC is essential to web users’ surfing and it is recommended to implement it.  Most companies that propose security audit regarding domain names consider DNSSEC as necessary and then as a notation criteria.

Do faster DNS increase the SEO?

Google admitted that the loading time of a web page has an impact on the SERP results. The times of the DNS research are in general less than a second, they can nevertheless affect the loading of a webpage in the following cases:

1. Recurring breakdowns on the DNS infrastructure

When a DNS cannot resolve or takes more time than usual, it can add many seconds to the time of a page loading. In case of lack of reliability and recurring unavailability, the impact on SEO is proved… Not mentioning the user experience in front of these repetitive failures (increase of the bounce rate, decrease of customers’ retention and impact on the trust in the brand, if not revenue loss). It is important to rely on a reliable and trustworthy infrastructure.

2. Quality of the network and points of presence

This is purely and simply physics, the nearest a names server is to the final user, the less time is needed to respond to its request. The DNS networks called “anycast” (optimized addressing and routing towards “the nearest” or the “more efficient” server) with many points of presence in the world, allow to optimize the response time depending on the geographical location.

Another important point is to have at least three names servers that are authority (SOA) for a domain name, ideally based on different domain names and TLDs, in order to reduce the risk of SPOF (Single Point of Failure) of an infrastructure. Indeed, if an infrastructure relies on the same domain name, an unavailability of this domain name, for whatever the reason, leads to the unavailability of the DNS infrastructure. Likewise, at the TLDs’ level and even if it is less likely, a problem of registry availability would affect all the DNS infrastructure.

3. Be careful of “extended” DNS configurations

It’s not unusual to have DNS configurations which send towards a final destination through several steps like in the example below.  As a consequence, the resolution time is affected and potentially, the performance in terms of SEO.

fr.wikipedia.org. IN CNAME text.wikimedia.org.

text.wikimedia.org. IN CNAME text.esams.wikimedia.org.

text.esams.wikimedia.org. IN A 91.198.174.232

Conclusion

The SEO is a science to consider as a whole. Thus, as we have seen through the impact of the HTTPS adoption of a website, this is a referencing factor among others and all things being equal, then this is particularly important in order to achieve a competitive edge on the first page of results.

The same applies to the impact of DNS on the SEO. Can the DNS have an impact? Yes, it clearly can in the case of incorrect configurations, or in the case that the DNS infrastructures do not allow response times fast enough. A DNS infrastructure called anycast is essential for any domain name carrying an important web traffic, even more at an international level. This is a data to integrate in a whole, and this thinking should be in a global approach of the SEO with the web marketing team.