Use F5 Distributed Cloud to control Primary and Secondary DNS

Overview

Domain Name Service (DNS); it's how humans and machines discover where to connect. DNS on the Internet is the universal directory of addresses to names. If you need to get support for the product Acme, you go to support.acme.com. Looking for the latest headlines in News, try www.aonn.com or www.npr.org. DNS is the underlying feature that nearly every service on the Internet depends on. Having a robust and reliable DNS provider is critical to keeping your organization online and working, and especially so during a DDoS attack.

F5 Distributed Cloud DNS (F5 XC DNS) can function as both Primary or Secondary nameservers, and it natively includes DDoS protection. Using F5 XC DNS, it’s possible to provision and configure primary or secondary DNS securely in minutes. Additionally, the service uses a global anycast network and is built to scale automatically to respond to large query volumes. Dynamic security is included and adds automatic failover, DDoS protection, TSIG authentication support, and when used as a secondary DNS—DNSSEC support.

F5 Distributed Cloud allows you to manage all of your sites as a single “logical cloud” providing:
-       A portable platform that spans multiple sites/clouds
-       A private backbone connects all sites
-       Connectivity to sites through its nodes (F5 Distributed Cloud Mesh and F5 Distributed Cloud App Stack)
-       Node flexibility, allowing it to be virtual machines, live on hardware within data centers, sites, or in cloud instances (e.g. EC2)
-       Nodes provide vK8s (virtual K8s), network and security services
-       Services managed through F5 Distributed Cloud’s SaaS base console

Scenario 1 – F5 Distributed Cloud DNS: Primary Nameserver

Consider the following; you're looking to improve the response time of your app with a geo-distributed solution, including DNS and app distribution. With F5 XC DNS configured as the primary nameserver, you’ll automatically get DNS DDoS protection, and will see an improvement in the response the time to resolve DNS just by using Anycast with F5’s global network’s regional point of presence.
 
To configure F5 XC DNS to be the Primary nameserver for your domain, access the F5 XC Console, go to DNS Management, and then Add Zone. Alternately, if you're migrating from another DNS server or DNS service to F5 XC DNS, you can import this zone directly from your DNS server. Scenario 1.2 below illustrates how to import and migrate your existing DNS zones to F5 XC DNS. Here, you’ll write in the domain name (your DNS zone), and then View Configuration for the Primary DNS.

On the next screen, you may change any of the default SOA parameters for the zone, and any type of resource record (RR) or record sets which the DNS server will use to respond to queries. For example, you may want to return more than one A record (IP address) for the frontend to your app when it has multiple points of presence. To do this, enter as many IP addresses of record type A as needed to send traffic to all the points of ingress to your app. Additional Resource Record Sets allows the DNS server to return more than a single type of RR. For example, the following configurations, returns two A (IPv4 address) records and one TXT record to the query of type ANY for “al.demo.internal”.

Optionally, if your root DNS zone has been configured for DNSSEC, then enabling it for the zone is just a matter of toggling the default setting in the F5 XC Console.

Scenario 1.2 - Import an Existing Primary Zone to Distributed Cloud using Zone Transfer (AXFR)

F5 XC DNS can use AXFR DNS zone transfer to import an existing DNS zone. Navigate to DNS Management > DNS Zone Management, then click Import DNS Zone.

Enter the zone name and the externally accessible IP of the primary DNS server.
➡️ Note: You'll need to configure your DNS server and any firewall policies to allow zone transfers from F5. A current list of public IP's that F5 uses can be found in the following F5 tech doc.

Optionally, configure a transaction signature (TSIG) to secure the DNS zone transfer. When you save and exit, F5 XC DNS executes a secondary nameserver zone AXFR and then transitions itself to be the zone's primary DNS server.

To finish the process, you'll need to change the NS records for the zone at your domain name registrar. In the registrar, change the name servers to the following F5 XC DNS servers:

ns1.f5clouddns.com
ns2.f5clouddns.com

 

Scenario 1.3 - Import Existing (BIND format) Primary Zones directly to Distributed Cloud

F5 XC DNS can directly import BIND formatted DNS zone files in the Console, for example, db.2-0-192.in-addr.arpa and db.foo.com. Enterprises often use BIND as their on-prem DNS service, importing these files to Distributed Cloud makes it easier to migrate existing DNS records.

To import existing BIND db files, navigate to DNS Management > DNS Zone Management, click Import DNS Zone, then "BIND Import".

Now click "Import from File" and upload a .zip with one or more BIND db zone files. The import wizard accepts all primary DNS zones and ignores other zones and files.

After uploading a .zip file, the next screen reports any warnings and errors At this poing you can "Save and Exit" to import the new DNS zones or cancel to make any changes.

For more complex zone configurations, including support for using $INCLUDE and $ORIGIN directives in BIND files, the following open source tool will convert BIND db files to JSON, which can then be copied directly to the F5 XC Console when configuring records for new and existing Primary DNS zones.

 

BIND to XC-DNS Converter

 

Scenario 2 - F5 Distributed Cloud DNS: Primary with Delegated Subdomains

An enhanced capability when using Distributed Cloud (F5 XC) as the primary DNS server for your domains or subdomains, is to have services in F5 XC dynamically create their own DNS records, and this can be done either directly in the primary domain or the subdomains. Note that before July 2023, the delegated DNS feature in F5 XC required the exclusive use of subdomains to dynamically manage DNS records. As of July 2023, organizations are allowed to have both F5 XC managed and user-managed DNS resource records in the same domain or subdomain.

When "Allow HTTP Load Balancer Managed Records" is checked, DNS records automatically added by F5 XC appear in a new RR set group called x-ves-io-managed which is read-only. In the following example, I've created an HTTP Load Balanacer with the domain "www.example.f5-cloud-demo.com" and F5 XC automatically created the A resource record (RR) in the group x-ves-io-managed.

Scenario 3 – F5 Distributed Cloud DNS: Secondary Nameserver

In this scenario, say you already have a primary DNS server in your on-prem datacenter, but due to security reasons, you don’t want it to be directly accessible to queries from the Internet. F5 XC DNS can be configured as a secondary DNS server and will both zone transfer (AXFR, IXFR) and receive (NOTIFY) updates from your primary DNS server as needed.
 
To configure F5 XC DNS to be a secondary DNS server, go to Add Zone, then choose Secondary DNS Configuration. Next, View Configuration for it, and add your primary DNS server IP’s. To enhance the security of zone transfers and updates, F5 XC DNS supports TSIG encrypted transfers from the primary DNS server. To support TSIG, ensure your primary DNS server supports encryption, and enable it by entering the pre-shared key (PSK) name and its value. The PSK itself can be blindfold-encrypted in the F5 XC Console to prevent other Console admins from being able to view it. If encryption is desired, simply plug in the remaining details for your TSIG PSK and Apply.

Once you’ve saved your new secondary DNS configuration, the F5 XC DNS will immediately transfer your zone details and begin resolving queries on the F5 XC Global Network with its pool of Anycast-reachable DNS servers.

Conclusion

You’ve just seen how to configure F5 XC DNS both as a primary DNS as well as a secondary DNS service. Ensure the reachability of your company with a robust, secure, and optimized DNS service by F5. A service that delivers the lowest resolution latency with its global Anycast network of nameservers, and one that automatically includes DDoS protection, DNSSEC, TSIG support for secondary DNS.

Watch the following demo video to see how to configure F5 XC DNS for scenarios #1 and #3 above.

 

 

 

Additional Resources

For more information about using F5 Distributed Cloud DNS: https://www.f5.com/cloud/products/dns
For technical documentation: https://docs.cloud.f5.com/docs/how-to/app-networking/manage-dns-zones
DNS Management FAQ: https://f5cloud.zendesk.com/hc/en-us/sections/7057223802519-DNS-Management
DNS Demo Guide and step-by-step walkthrough: https://github.com/f5devcentral/f5xc-dns

BIND to XC-DNS Converter (open source tool): https://github.com/Mikej81/BINDtoXCDNS