---
title: Registering Custom Nameservers
description: "Domain Management Guide ## Overview This procedure describes how to switch the nameserver for your target domain from the BESTNET [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/) to an **external DNS server (external DNS hosting)**. When you change nameservers, the DNS record reference destination (authoritative…"
url: "https://bestnetllc.co.jp/en/docs/registering-custom-nameservers/"
updated: "2026-10-19"
category: domain
---

# Registering Custom Nameservers

Domain Management Guide

## Overview

This procedure describes how to switch the nameserver for your target domain from the BESTNET [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/) to an **external DNS server (external DNS hosting)**.

When you change nameservers, the DNS record reference destination (authoritative DNS) switches to the external DNS side. After the switch, **DNS records configured on our side will no longer be referenced**, so **please prepare zones (DNS records) on the external DNS side beforehand** before proceeding.

   STEP 1 **Prepare external DNS**

Complete zone creation and register necessary records on the external DNS side.

   STEP 2 **Enter nameservers**

Set custom nameservers in the [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/).

   STEP 3 **Save and verify**

After saving settings, verify the NS and record switch status from external sources.

## Important (Read First: How to Prevent Accidents)

- **Nameserver switching = completely switching the reference destination**. If external DNS configuration is incomplete at the time of switching, web, email, and various authentications will be immediately affected.
- Common migration oversights include **email (MX / SPF / DKIM / DMARC)**, **authentication TXT records** (Google / Microsoft / various SaaS), **SSL renewal TXT (_acme-challenge)**, **CAA**, and **SRV**.
- Before performing the switch, note down your current DNS settings (on our side / other services) and **create equivalent records on the external DNS side**.
- For domains with DNSSEC enabled, **DS record updates / deletions** may be necessary during the switch (see details below).

## Disclaimer and Support Information

- This procedure summarizes common operational examples. Depending on your domain configuration and external service usage (email, various SaaS, SSL auto-renewal, etc.), required DNS records and migration procedures may differ.
- We are not responsible for indirect or consequential damages (business loss, downtime, email delivery failures, etc.) resulting from following this procedure.
- **If you have unclear points / if it is difficult to determine the scope of impact / if DNSSEC is enabled / if you are switching email as well**, please **open a [support ticket](https://bestnetllc.co.jp/en/encyclopedia/support-ticket-en/) from the BESTNET [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/)** before proceeding.

## Preparation

- Hostname(s) of nameserver(s) (typically 2 or more) provided by the external DNS service
- Zone creation and record configuration for the target domain on the external DNS side must be complete

## Pre-Switch Checklist (Recommended: Complete Before Switching)

- **Zone created on external DNS side** (root zone like `example.com`)
- **Current DNS records noted down** (A / AAAA / CNAME / MX / TXT / CAA / SRV / NS delegation, etc.)
- **Necessary records created on external DNS side** (especially MX / SPF / DKIM / DMARC, various authentication TXT, `_acme-challenge`)
- **TTL reduction** completed in advance if possible (to minimize impact on switch day)
  ※TTL reduction should be done first on the “current authoritative DNS side,” and may take time to propagate.
- **DNSSEC presence** confirmed (if enabled, refer to “DNSSEC Precautions”)
- **Double-check spelling** of nameserver hostnames provided by external DNS (copy-paste recommended)

## Operation Steps ([client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/))

### 1Open the target domain details screen

1. Log in to the [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/).
2. From the dashboard **domain list**, click the right-end icon (→) on the target domain row to open the details screen.

![Open the target domain details screen](https://bestnetllc.co.jp/wp-content/uploads/2025/12/step-01-open-domain-details.png)
Open the target domain details screen

### 2Navigate to the “Nameserver Management” section

1. Scroll down on the domain details screen and click the link (Nameserver) at the bottom of the **Nameserver** section.
2. Navigate to the **Nameserver Management** section on the page.

![Open nameserver management section](https://bestnetllc.co.jp/wp-content/uploads/2025/12/step-02-open-nameserver-management.png)
Navigate to the Nameserver Management section

### 3Select “Custom”

1. In the **Nameserver Management** section, select **Custom**.

![Select custom in nameserver settings](https://bestnetllc.co.jp/wp-content/uploads/2025/12/step-03-select-custom.png)
Select custom nameserver

### 4Enter external DNS server (nameserver)

1. Enter the nameservers provided by the external DNS service (typically 2 or more).
2. Enter in hostname format (e.g., `dns1.example.net`).

  **Input Notes**

- Basically, enter **hostname only** (not IP addresses).
- Some external DNS providers provide 3 or more nameservers. Enter all that are provided.
- Even if the notation includes a trailing dot (`.`), it may not be necessary depending on the input field specification (follow the provider’s instructions and this screen’s specifications).

   **Input Example**

- Nameserver 1: dns1.cloudns.net
- Nameserver 2: dns2.cloudns.net
- (As needed) Nameserver 3 and beyond

![Enter external DNS nameservers](https://bestnetllc.co.jp/wp-content/uploads/2025/12/step-04-enter-external-nameservers.png)
Enter external DNS server values

### 5Save changes

1. Click **Save Changes**.
2. When the completion message is displayed, the operation is complete.

![Save nameserver changes](https://bestnetllc.co.jp/wp-content/uploads/2025/12/step-05-save-changes.png)
Save changes and complete

## DNSSEC Precautions (If Applicable)

- If DNSSEC is enabled on the target domain, **DS record inconsistencies** may occur after nameserver switching, which can cause name resolution failures.
- To continue DNSSEC, it may be necessary to update DS information to match the external DNS side’s DNSKEY.
- If determining this is difficult, please **open a [support ticket](https://bestnetllc.co.jp/en/encyclopedia/support-ticket-en/) from the BESTNET [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/)** before proceeding.

## Verification Method

- Reload the same page and verify that the nameserver list matches the values you entered.
- DNS switching may take time to propagate. Also verify that records on the external DNS side are correctly configured.

External Verification Examples (Recommended)

  `dig NS example.com` `dig +trace example.com` `dig A example.com` `dig A www.example.com` `dig MX example.com`

## Precautions (Common Pitfalls)

   **Entered a non-existent nameserver**

The update will fail. Enter the correct hostname provided by the external DNS service.

   **External DNS configuration incomplete**

Once you switch nameservers, the **external DNS side’s zones (DNS records)** will be referenced thereafter. Always complete external DNS configuration before switching.

   **Using nameservers under your own domain**

With configurations like `ns1.yourdomain`, separate **nameserver registration (glue records)** may be required.

   **Email-related record migration oversights**

**If you use email**, always verify that MX / SPF / DKIM / DMARC are all present on the external DNS side.

## When You Need Help (Open a [support ticket](https://bestnetllc.co.jp/en/encyclopedia/support-ticket-en/))

If you have questions or encounter unresolved issues after switching, please **open a [support ticket](https://bestnetllc.co.jp/en/encyclopedia/support-ticket-en/) from the BESTNET [client portal](https://bestnetllc.co.jp/en/encyclopedia/client-portal-en/)**.

Including the following will make verification smoother.

- Target domain name
- External DNS service name (e.g., Cloudflare / Route53, etc.)
- Configured nameserver values (copy-paste)
- External verification results (e.g., results of `dig NS example.com` / `dig +trace example.com`)
- Symptoms occurring (web not visible / email not delivered, etc.) and time of occurrence