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Computer networking is made possible through the domain name system (DNS). Without the DNS, all networked communications would be brought to a standstill. Active Directory (AD) also relies on a proper DNS infrastructure for effective operation. A poorly configured DNS leads to a wide range of issues like authentication and replication failures, preventing new computers from being added to your domain, Group Policy processing problems, and more. Here are nine DNS server best practices that will help you avoid a complete DNS failure.
Having just one DNS server in your site can affect the functioning of your entire AD environment when that server goes down. Ensure redundancy by setting up at least two DNS servers in a site, so that even if the primary server runs into an issue, the secondary server takes over immediately without disrupting critical services.
By installing the DNS server role on a domain controller (DC), you can capitalize on AD-integrated zones which simplify DNS replication and offer improved security. These zones store data in directory partitions within the AD database. This data is replicated along with the rest of AD, eliminating the need to configure zone transfers. AD-integrated zones also allow secure dynamic updates, preventing unauthorized clients from updating the DNS records.
For a DNS server, setting its loopback address as a primary DNS improves its performance and increases its availability. However, for a DC with a DNS role, Microsoft suggests that its primary DNS point to any other DC in the site and secondary DNS point to itself (loopback address). This prevents any delays during start-up.
In a domain, all devices should be able to communicate with each other. This is achieved only when the domain-joined computers are configured to use internal DNS servers for name resolution, as external DNS servers cannot resolve hostnames for internal devices. In internal environments, set both the primary and secondary DNS to internal nameservers on all client machines in the domain.
In a large organization, client machines querying a remote server from a different site with a DNS request increases the response time. This is because the query travels across slower WAN links leading to longer load times for users. In a multi-site environment, it is best to point the client machines to a local DNS server within the site to reduce the response time.
It is possible for client machines to register multiple DNS entries during relocation, or when they are removed and added back to the domain. This can result in name resolution problems leading to connectivity issues. Configuring aging and scavenging ensures that the stale DNS records (DNS records not in use) are removed from the DNS automatically.
DNS logs help monitor DNS activity effectively. Besides tracking client activity, they provide essential information on problems involving DNS errors, queries, or updates. DNS debug logs also highlight traces of cache poisoning which occurs when an attacker meddles with the DNS data stored in the cache, causing clients to be redirected to malicious sites. Although DNS debug logging has an impact on the overall server performance, it is recommended that you enable it to enhance DNS security.
DNS server data is sensitive information waiting to be exploited by attackers. That's why it's important to secure your DNS servers by allowing access only to your administrators. This can be accomplished by configuring the ACLs to allow inbound connections to nameservers only from specific hosts so that authorized users alone can access your DNS servers.
In a large IT environment, any changes to the DNS can easily go unnoticed. When such changes are made by malicious users, the security of the entire network is compromised. Keep tabs on all changes to your DNS nodes, zones, and permissions to ensure a secure AD environment.