This topic describes the default behavior of the Consul DNS functionality and how to customize how Consul performs queries.
## Introduction
The Consul DNS is the primary interface for querying records when Consul service mesh is disabled and your network runs in a non-Kubernetes environment. The DNS enables you to look up services and nodes registered with Consul using terminal commands instead of making HTTP API requests to Consul. Refer to the [Discover Consul Nodes and Services Overview](/consul/docs/services/discovery/dns-overview) for additional information.
By default, the Consul DNS listens for queries at `127.0.0.1:8600` and uses the `consul` domain. Specify the following parameters in the agent configuration to determine DNS behavior when querying services:
- [`ports.dns`](/consul/docs/agent/config/config-files#dns_port) : Consul does not use port `53`, which is typically reserved for the default port for DNS resolvers, by default because it requires an escalated privilege to bind to.
By default, Consul DNS queries return a node's local address, even when being queried from a remote datacenter. You can configure the DNS to reach a node from outside its datacenter by specifying the address in the following configuration fields in the Consul agent:
You can specify a list of addresses in the agent's [`recursors`](/consul/docs/agent/config/config-files#recursors) field to provide upstream DNS servers that recursively resolve queries that are outside the service domain for Consul.
Nodes that query records outside the `consul.` domain resolve to an upstream DNS. You can specify IP addresses or use `go-sockaddr` templates. Consul resolves IP addresses in the specified order and ignores duplicates.
We recommend that you configure DNS resolvers to point the `consul.` domain towards your Consul DNS servers. Misconfigurations may cause other DNS infrastructure to route queries for the `consul.` domain outside of your network instead, leaking DNS queries to root DNS servers. Refer to [Forward DNS for Consul Service Discovery](/consul/tutorials/networking/dns-forwarding) for instructions.
You enable non-Consul queries to be resolved by setting Consul as the DNS server for a node and providing a [`recursors`](/consul/docs/agent/config/config-files#recursors) configuration.
You can forward all queries sent to the `consul.` domain from the existing DNS server to a Consul agent. Refer to [Forward DNS for Consul Service Discovery](/consul/tutorials/networking/dns-forwarding) for instructions.
### Query an alternate domain
By default, Consul responds to DNS queries in the `consul` domain, but you can set a specific domain for responding to DNS queries by configuring the [`domain`](/consul/docs/agent/config/config-files#domain) parameter.
You can also specify an additional domain in the [`alt_domain`](/consul/docs/agent/config/config-files#alt_domain) agent configuration option, which configures Consul to respond to queries in a secondary domain. Configuring an alternate domain may be useful during a DNS migration or to distinguish between internal and external queries, for example.
Responses to pointer record (PTR) queries, such as `<ip>.in-addr.arpa.`, always use the [primary domain](/consul/docs/agent/config/config-files#domain) and not the alternative domain.
By default, DNS results served by Consul are not cached. Refer to [DNS caching](/consul/docs/services/discovery/dns-cache) for instructions on how to enable caching.
