--- title: "DNS Migration FAQ" sidebar_label: "DNS Migration FAQ" sidebar_position: 99 description: "Frequently asked questions about DNS migration" --- import Formbricks from '@theme/MDXComponents/Formbricks'; # DNS Migration FAQ ## Where are the authoritative DNS servers for our domains located, and how is their fault tolerance ensured? \{#ns-servers-location} Domain zones added to [DNS Hosting](/dns-hosting/) are served by four authoritative NS servers: `a.ns.selectel.ru`, `b.ns.selectel.ru`, `c.ns.selectel.ru`, `d.ns.selectel.ru`. The servers are located in data centers in Saint Petersburg and Moscow, run on dedicated hosts, and are announced via BGP. Fault tolerance is ensured through: * firewall protection of servers against DDoS attacks; * load balancing of requests within each data center and between data centers. DNS Hosting processes requests as long as at least one authoritative server is operational. For more information, see the [Authoritative servers](/dns-hosting/about-dns.mdx#selectel-ns-servers) subsection in the [General information about DNS Hosting](/dns-hosting/about-dns.mdx) instructions. If your domains use DNS Hosting (legacy) with NS servers `ns1.selectel.ru` – `ns4.selectel.ru`, [migrate them to DNS Hosting (actual)](/dns-hosting/move-domain/move-from-legacy-to-actual.mdx). According to the [DNS Hosting (legacy) shutdown stages](/dns-hosting/about-dns.mdx#legacy-shutdown-stages), its authoritative NS servers will be decommissioned on December 1, 2026. ## Will DNS continue to work if ru-3 and ru-9 are unavailable simultaneously? \{#pools-unavailable} DNS Hosting is not tied to [pools](/infrastructure/locations.mdx#pool) and regions where your resources are located. The ru-3 and ru-9 pools are located in different availability zones of the Saint Petersburg region, while authoritative servers are located in data centers in Saint Petersburg and Moscow. Therefore, even if both pools become unavailable simultaneously, domain zones will continue to be served by servers in Moscow. ## Will we be able to modify DNS records and redirect domains to a disaster recovery environment if regions and the cloud control panel fail? \{#change-records-on-outage} DNS query processing does not depend on cloud pool availability: authoritative servers run on dedicated hosts, are announced via BGP, and will continue to respond to queries for domain zones. You can redirect a domain to a disaster recovery environment by changing resource records, such as A or AAAA records. For more information, see the [Transfer a site to a new IP address](/dns-hosting/records/move-to-new-ip.mdx) instructions. You can edit records in the [Control panel](https://my.selectel.ru/dns/default/hosting) or using: * [DNS Hosting API](/api/dns-actual/); * [Terraform](/terraform/providers/) (beta); * [octoDNS](https://github.com/octodns/octodns-selectel) (beta); * [Selectel provider for ExternalDNS](https://github.com/selectel/external-dns-selectel-webhook). Keep in mind that changes propagate within a period ranging from the record group TTL up to 72 hours. ## Is there automatic switching of DNS records based on availability check results? If so, what are the expected switching times and limitations, including those related to TTL and caching? \{#automatic-failover} DNS Hosting does not check the availability of your domains and services and does not modify resource records based on check results. You can set up switching manually by configuring monitoring and automatic record modification via the [DNS Hosting API](/api/dns-actual/), [Terraform](/terraform/providers/), or [octoDNS](https://github.com/octodns/octodns-selectel). The following limitations apply: * TTL is set for a resource record group and applies to all records in the group; * changes propagate within a period ranging from the group TTL up to 72 hours, and recursive servers worldwide may return the old record value until the cache TTL expires. To speed up the switchover, a few days in advance, [reduce the record TTL to the minimum possible value](/dns-hosting/records/edit-record.mdx), and restore the previous value after the switchover. ## What DNS dependencies on regional infrastructure or provider management services should be considered? \{#dependencies} There are no additional dependencies on regional infrastructure: DNS Hosting is geographically distributed, redundant, and does not depend on the pools and regions where your resources are located. Management services (control panel, API) only affect resource record modification — control panel unavailability does not affect DNS query processing. Consider factors external to Selectel infrastructure: * zone delegation — domain records are served from Selectel NS servers only as long as Selectel NS servers are specified at the domain registrar. You can verify that the zone is delegated by checking the zone status in the control panel; for more information, see the [View zone status](/dns-hosting/zones/check-zone-status.mdx) instructions; * caching on recursive servers — resource record changes take from the record group TTL up to 72 hours to propagate; * service limitations: Selectel DNS cannot be used as Secondary DNS, and reverse records (PTR) are managed outside of DNS Hosting. For more information, see the [Limitations](/dns-hosting/about-dns.mdx#limitations) subsection in the [General information about DNS Hosting](/dns-hosting/about-dns.mdx) instructions.