DNS Configuration

Overview

DNS configuration in Polystack 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

Configure DNS on a Subnet

Dashboard
CLI

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.

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.

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.

Authenticate

Source your credentials file to authenticate with the Polystack platform:

Load credentials

source openrc.sh

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

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.

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.

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
Verify resolution

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

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.

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.

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, Polystack Networking supports the optional DNS service (Polystack DNS) which provides zone management, record lifecycle, and floating IP-to-hostname associations. Contact your administrator to enable Polystack DNS.

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

Core Services

Other Services

Overview

Configure DNS on a Subnet

Open the subnet for editing

Update DNS

Save and verify

Authenticate

Set DNS resolvers on a subnet

Verify the configuration

Apply DNS Changes to Running Instances

Remove DNS Resolvers

DNS Reference

Next Steps

Create and Manage Subnets

Network Troubleshooting

Floating IP Addresses

Network Topologies

​Overview

​Configure DNS on a Subnet

Open the subnet for editing

Update DNS

Save and verify

Authenticate

Set DNS resolvers on a subnet

Verify the configuration

​Apply DNS Changes to Running Instances

​Remove DNS Resolvers

​DNS Reference

​Next Steps

Create and Manage Subnets

Network Troubleshooting

Floating IP Addresses

Network Topologies

Overview

Configure DNS on a Subnet

Apply DNS Changes to Running Instances

Remove DNS Resolvers

DNS Reference

Next Steps