DNS Configuration

Configure DNS name servers and hostname resolution for NxtSight tenant subnets. Push resolvers to instances via DHCP for private and public name resolution.

Overview

DNS configuration in NxtSight Networking controls which resolvers instances use for hostname resolution. Name servers are set at the subnet level and pushed to instances via DHCP at boot time. You can configure private internal resolvers, public fallback resolvers, or a combination — giving instances access to both internal service hostnames and public domain names.

Prerequisites

• An existing subnet with DHCP enabled (Create and Manage Subnets)
• Dashboard access or CLI configured with valid credentials

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Configure DNS on a Subnet

Dashboard

1. Open the subnet for editing

   Navigate to Network > Networks. Click the network name, open the Subnets tab, and click Edit Subnet on the target subnet.

2. Update DNS

   In the Advanced Options section, update the DNS field. Enter one resolver per line.

   Resolver Type	Example	Use Case
   Internal resolver	10.0.0.53	Resolve private hostnames (e.g., db.internal)
   Public fallback	8.8.8.8	Resolve public internet domains
   Secondary public	8.8.4.4	Redundant public resolver

   Place your internal resolver first. Instances try resolvers in the order they are listed — putting the internal resolver first speeds up private hostname lookups.

3. Save and verify

   Click Save. Existing instances pick up the new resolvers on their next DHCP renewal.

   New instances launched on this subnet receive the updated DNS resolvers automatically.

CLI

1. Authenticate

   Source your credentials file to authenticate with the NxtSight platform:

   Load credentials

   source openrc.sh
   

   Your administrator provides the RC (credentials) file for your project. See CLI Setup for configuration details.

2. Set DNS resolvers on a subnet

   Update DNS name servers

   openstack subnet set app-subnet \
     --dns-nameserver 10.0.0.53 \
     --dns-nameserver 8.8.8.8
   

   Repeat --dns-nameserver for each resolver. The order of the flags determines the resolver priority.

3. Verify the configuration

   Show subnet DNS config

   openstack subnet show app-subnet -f json | grep dns_nameservers
   

   Output lists the configured resolvers in priority order.

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Apply DNS Changes to Running Instances

DNS resolvers are delivered via DHCP at instance boot. Running instances retain their current resolvers until their DHCP lease renews or you force a renewal.

Linux instances

Force DHCP renewal (systemd-networkd)

sudo networkctl renew eth0

Force DHCP renewal (NetworkManager)

sudo nmcli device reapply eth0

Force DHCP renewal (dhclient)

sudo dhclient -r eth0 && sudo dhclient eth0

Verify resolution

After renewal, confirm the instance is using the updated resolvers:

Check /etc/resolv.conf

cat /etc/resolv.conf

Test internal resolution

nslookup db.internal 10.0.0.53

Test public resolution

nslookup google.com 8.8.8.8

Both internal and public hostnames resolve correctly.

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Remove DNS Resolvers

Clear DNS name servers from subnet

openstack subnet set app-subnet --no-dns-nameservers

Removing all DNS resolvers means instances will have no resolvers after their next DHCP renewal. They will be unable to resolve any hostnames, including internal ones. Always configure at least one resolver.

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DNS Reference

Resolver	Address	Notes
Google Public DNS	8.8.8.8, 8.8.4.4	Low-latency, widely available
Cloudflare DNS	1.1.1.1, 1.0.0.1	Privacy-focused, fast
Internal (example)	10.0.0.53	Resolves private hostnames within your cluster

For deployments with a dedicated DNS service, NxtSight Networking supports the optional DNS service (NxtSight DNS) which provides zone management, record lifecycle, and floating IP-to-hostname associations. Contact your administrator to enable NxtSight DNS.

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Next Steps

Create and Manage Subnets

Manage all subnet settings including DHCP, allocation pools, and host routes

Network Troubleshooting

Diagnose DHCP and name resolution failures on your instances

Floating IP Addresses

Assign public IPs to instances with DNS-resolvable hostnames

Network Topologies

Design multi-tier topologies with DNS-aware subnets