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Managing DNS changes for Arc XP Delivery

This guide provides technical information regarding DNS entries and how to use the records that Arc XP provides you as part of a site launch. For information on the various methods you can use to launch your site on Arc XP see Migrating site traffic to Arc XP.

Understanding DNS

It's important to understand the key terms related to DNS before diving into the DNS process.

  • Domain Name System (DNS) - a system that translates human-readable domain names (like example.com) into IP addresses (like 192.0.2.1) that computers use to locate servers. DNS ensures you don't need the IP address to visit a website.

  • Fully Qualified Domain Name (FQDN) - the complete domain name that points to a specific host in the DNS hierarchy. For example, www.example.com is the FQDN. An FQDN is required in DNS records because it uniquely identifies a resource on the internet.

  • IP address - identifies a server or device on the internet. Today, two IP formats are common:

    • IPv4, for example, 192.0.2.1, is an older format with 32-bit addresses.

    • IPv6, for example, 0000:0000:0000:0000:0000:ffff:c000:0201, is a newer format with 128-bit addresses.

  • A record (Address record) - maps an FQDN to an IPv4 address. For example:

    example.com   IN   A    192.0.2.1

  • AAAA record - similar to an A record, but maps an FQDN to an IPv6 address. For example:

    example.com   IN   AAAA   0000:0000:0000:0000:0000:ffff:c000:02012606:2800:220:1:248:1893:25c8:1946

  • CNAME (Canonical Name) record - an alias that points one domain name to another. A CNAME doesn't point to an IP address directly but instead redirects to another FQDN that has an A or AAAA record. For example:

    www.example.com   IN   CNAME   example.com.

    Note

    A CNAME cannot exist at the apex (root) of a domain. See Apex aliasing (or flattening).

  • Apex record - sometimes called the root domain record, an apex record points the root domain (example.com) to an IP address. Because the root domain is at the top of the DNS hierarchy, it cannot be a CNAME. It must have an A or AAAA record. For example:

    example.com   IN   A   192.0.2.1

  • DNS TTL (time to live) - a setting that controls how long DNS records are cached before devices or DNS servers check for updates.

Now, let's bring these terms together in a simple example:

  1. You enter the FQDN of www.example.com in your browser.

  2. Your browser asks the DNS resolver for the IP address.

  3. The DNS resolver checks if www.example.com is:

    • an A or AAAA record - it returns the IP address directly.

    • a CNAME - it follows the alias (for example, www.example.com to example.com)

  4. If it's a CNAME, the resolver queries for the A record or AAAA record at example.com.

  5. The DNS resolver caches the result for the specified TTL to reduce future lookups.

  6. Your browser connects to the returned IP address and loads the website.

This all happens in a matter of seconds, or, at Arc XP, in a matter of milliseconds.

Note

DNS contains other concepts, such as NS servers, authoritative servers, and recursive lookups, which we don't cover here as they're used only when registering new domains. For a more in-depth view of DNS, see AWS's What is DNS?.

Apex aliasing (or flattening)

Many websites operate without a www or similar subdomain, using the FQDN of the root domain instead. When integrating with CDN or SaaS providers that offer only CNAME records for DNS (like Arc XP), there are solutions that can help.

Your DNS admins should check whether your service provider supports apex aliasing. Apex aliasing allows you to set an FQDN as an alias for your root domain. When a user tries to access the apex domain, the DNS provider performs a recursive lookup on the alias, retrieves the corresponding A records, and returns them to the user. This approach ensures that RFC 1034 (a standard of how DNS functions) is respected, keeping everything compliant and functioning correctly.

Concerns with apex aliasing

The main issue with apex aliasing is that the IP addresses returned depend on how your DNS provider performs the server-side lookup.

For example, Arc XP uses a global CDN with thousands of nodes. Normally, when a user resolves a domain with a CNAME, they are directed to the node closest to them based on geographic location. However, with apex aliasing, the DNS provider performs the lookup from its own location. This means the IP addresses returned may be based on the provider’s location, not the end user’s. As a result, users could be directed to a server far from their geographic location, leading to slower performance.

Additionally, for high-traffic sites, aliasing can result in many users being directed to the same node instead of different nodes closer to them. This can overwhelm that node and cause degraded performance.

Because of these issues, Arc XP does not recommend using apex aliasing if you are choosing a new domain name or have flexibility with your domain. However, if changing your site’s FQDN is not possible due to SEO concerns, you should discuss high-performance options with Arc XP to ensure optimal service.

Adding a domain to Arc XP

You must set up all domains within Arc XP before launch. This includes both new and existing domains, even if they are already configured with a CNAME. You must add new domains to Arc XP before they can respond. Arc XP Customer Support can assist you in submitting requests to add your domain to your Arc XP site.

For apex domains, Arc XP recommends using an apex aliasing solution. If this isn't possible, contact Arc XP Customer Support to discuss alternative options, such as an Arc XP Apex box.

When adding a domain, Arc XP provides a CNAME for non-apex DNS names upon request. The CNAME target is the same for all hostnames within the same Site ID and Environment.

If you cannot use an apex aliasing solution but have an approved Arc XP Apex box, you receive an IP address to use for the apex record. Note that these IP addresses may vary between different Site IDs due to limitations on the number of names that can be provisioned together. In most cases, you have only one IP address, but it should not be assumed that all Site IDs will share the same IP.

Setting up a domain name using a CNAME

Most DNS providers offer a simple interface to enter resource records and corresponding alias (CNAME) entries. Use the arc-dns.net name provided and enter it for the specific domain requested from Arc XP. For example, if you requested www.example.com to be added to the Production Site ID “site” and sandbox.example.com to the Sandbox environment of Site ID “site,” your DNS entries should look as follows:

sandbox.example.com.   300   IN   CNAME   example-sandbox.arc-dns.net.
www.example.com.       300   IN   CNAME   example-prod.arc-dns.net.

Setting up a domain name using a CNAME alias

The process for setting up a CNAME alias varies depending on your DNS provider and how they implement aliasing. Most providers offer an interface where you can select a resource record type, such as “alias”, or, in the case of Akamai’s product, “akamaicdn”. Providers like UltraDNS or DynDNS may require using a separate interface for adding aliases.

Regardless of the provider or interface, the value for the resource record is the DNS name that Arc XP provides, such as example-prod.arc-dns.net, which would typically be used in a CNAME record. After entering the record, a DNS query returns a result like this:

example.com.            300   IN   A   192.0.2.1
example.com.            300   IN   A   192.0.2.1

The arc-dns.net name is not visible in the DNS response, as DNS RFCs require an A record response. To validate that the response is correct, you can perform a whois lookup on the IP addresses returned and confirm that the organization is Akamai Technologies, Inc.

Arc XP Apex box

An Arc XP Apex box is an IP address provided by Arc XP for clients who cannot use CNAME aliasing or flattening. You must request these hosts through Arc XP Customer Support with a valid reason explaining why aliasing or flattening isn’t possible. Apex boxes also come with important usage restrictions:

  • Not for primary domains - You cannot use Apex boxes for the main domain that users and search engines interact with. For example, if your public domain is example.com, you cannot use an Apex IP for this record. Instead, you must use a CNAME aliasing product or discuss alternative solutions with Arc XP.

  • For redirects only - Apex boxes are intended strictly for redirecting traffic to another domain. For example, you can use an Apex box to redirect example.com to www.example.com.

  • Limited load support - Apex boxes are designed to handle only the light traffic associated with redirection. Avoid generating internal site links that point to the Apex box’s domain, as this increases load on the Apex host and causes slower performance for users. Each visitor following those links would first hit the Apex server before being redirected to the live site.

  • CDN limitations - Because an Apex record points directly to an IP address, it bypasses the geographic benefits of a CDN. Ideally, only the initial request goes to the Apex box (for example, example.com) before redirecting to the main site (for example, www.example.com).

Understanding the *.arc-dns.net target

Arc XP assigns a unique subdomain under the *.arc-dns.net domain for each Site ID and environment you’re using. This setup offers flexibility for managing server changes without requiring you to manually update your DNS records.

At times, Arc XP may need to change the network of servers that your CNAME chain points to. Instead of asking you to update your DNS settings each time, Arc XP updates the *.arc-dns.net target internally. This ensures minimal disruption and improved performance.

For example, a DNS lookup (using dig) might show the following chain:

example-site-prod.arc-dns.net. 0 IN      CNAME   83320.edgekey.net.
83320.edgekey.net.             0 IN      CNAME   e33151.dscx.akamaiedge.net.
e33151.dscx.akamaiedge.net.    0 IN      A       23.212.250.76
e33151.dscx.akamaiedge.net.    0 IN      A       23.212.250.91

In this example:

  • The arc-dns.net record points to an intermediate CNAME (83320.edgekey.net).

  • This chain continues until it ultimately resolves to an IP address.

By using the *.arc-dns.net target, Arc XP can adjust CDN mappings internally to optimize performance without requiring you to modify your DNS settings. This design simplifies maintenance and ensures a smoother end-user experience.

Best practices when making DNS changes

DNS plays a vital role in web hosting, and any changes should be handled with care. Follow these steps carefully to minimize downtime and ensure a smooth transition.

We'll use the following example site: www.example.com

The goal is to update your DNS record to point to a new CNAME target provided by Arc XP, which looks like this:

www.example.com. 60 IN CNAME example-prod.arc-dns.net.

  1. Check the current content TTL.

    In your DNS management tool, check the current TTL value for your domain.

    • If the current TTL is greater than 5 minutes (300 seconds), reduce it to 5 minutes.

    • After you lower the TTL, wait for at least the original TTL period to ensure the change has propagated.

  2. Prepare for the change.

    Before proceeding with your DNS update:

    • Temporarily lower the TTL to 60 seconds.

    • Wait five minutes to ensure the new TTL is active.

    • Record your current DNS settings as a backup in case you need to revert the changes. To capture the current settings, run the following command.

      $ dig www.example.com
;; ANSWER SECTION:
www.example.com.  60 IN CNAME 54321.edgekey.net.

  3. Update your DNS record.

    Now you can safely update your DNS record to point to the new Arc XP-provided target. Use the dig command again to confirm the change has taken effect:

    $ dig www.example.com
;; ANSWER SECTION:
www.example.com.  60 IN  CNAME  example-prod.arc-dns.net.

    It may take a full minute for the change to appear after your DNS system processes it.

  4. Verify your site.

    After confirming the DNS change, check that your site is accessible in a browser. If your site isn’t reachable, revert the DNS change using the backup settings you recorded earlier and contact Arc XP Customer Support.

  5. Finalize your change.

    Once your DNS update is successful, notify Arc XP that you’ve made the change. Arc XP verifies your DNS records to ensure they are correct. After confirmation, increase your TTL to a higher value, ideally between 1 hour (3,600 seconds) and 24 hours (86,400 seconds) for improved stability.

  6. Perform a final confirmation.

    After increasing the TTL, run a final dig command to confirm the new settings:

    $ dig www.example.com
;; ANSWER SECTION:
www.example.com.  86400  IN  CNAME  example-prod.arc-dns.net.

    Finally, confirm your site is accessible in your browser.

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