This topic describes how Anthos clusters on AWS interacts with Domain Name Services (DNS) on both your AWS Virtual Private Cloud (VPC) and clusters.
AWS VPC DNS
This section describes how you can configure an AWS Virtual Private Cloud (VPC) for Anthos clusters on AWS (GKE on AWS).
Configuring VPC DNS
Anthos clusters on AWS supports a variety of DNS configurations in your AWS VPC. You configure your VPC's DNS settings when you Create a DHCP options set. For more information, see DNS support for your VPC.
You can configure the following options:
- DNS Hostnames
- This sets whether EC2 instances with public IP addresses get corresponding
public DNS hostnames. You set this value using the
enableDNSHostnamesfield in your VPC's DHCP option set. For more information, see VPC DNS Hostnames and DHCP options sets for your VPC.
- EC2 DNS Hostnames
- This sets whether EC2 instances receive a default DNS hostname or a custom DNS hostname.
- DNS server
- Whether your VPC's DHCP options set uses either the AWS Route53 DNS server
AmazonProvidedDNSoption), or a hosted DNS server.
Supported VPC DNS configurations
The following table includes DNS configurations supported by Anthos clusters on AWS:
|Enable DNS hostnames||EC2 DNS hostnames||DNS server||Supported?|
Service discovery is the process where workloads discover services without knowing their IP address. This section describes how Anthos clusters on AWS (GKE on AWS) implements service discovery and managed DNS.
Kubernetes automatically generates service names that use the following specification:
service: your service's name
namespace: your service's Namespace
zone: your service's AWS zone
Workloads also access external services— for example
using DNS names. For more information on the behavior of DNS in Kubernetes, see
DNS for Services and Pods.
Anthos clusters on AWS uses
to resolve DNS names within clusters. CoreDNS runs as a redundant, scaled
namespace. The CoreDNS deployment has a
Service that groups the CoreDNS Pods
and gives them a single IP address. The CoreDNS Deployment scales with the
cluster's size and usage.
Anthos clusters on AWS uses NodeLocal DNSCache to improve DNS lookup performance. NodeLocal DNSCache runs as a DaemonSet on each node in your cluster. When a Pod makes a DNS request, the request first goes to the DNS cache on the same node. If the cache can't resolve the DNS request, the cache forwards the request to either:
- CoreDNS for an internal name— for example
Amazon DNS server,
for an external name— for example
Anthos clusters on AWS uses Calico to establish BGP routing between cluster nodes.
- Read about AWS DNS support for your VPC.
- For an overview of how DNS is used in Kubernetes clusters, see DNS for Services and Pods.