mirror of https://github.com/hashicorp/consul
77 lines
4.4 KiB
Markdown
77 lines
4.4 KiB
Markdown
---
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layout: docs
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page_title: Configure Consul DNS behavior
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description: ->
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Learn how to modify the default DNS behavior so that services and nodes can easily discover other services and nodes in your network.
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---
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# Configure Consul DNS behavior
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This topic describes the default behavior of the Consul DNS functionality and how to customize how Consul performs queries.
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## Introduction
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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.
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## Configure DNS behaviors
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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:
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- [`client_addr`](/consul/docs/agent/config/config-files#client_addr)
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- [`ports.dns`](/consul/docs/agent/config/config-files#dns_port)
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- [`recursors`](/consul/docs/agent/config/config-files#recursors)
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- [`domain`](/consul/docs/agent/config/config-files#domain)
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- [`alt_domain`](/consul/docs/agent/config/config-files#alt_domain)
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- [`dns_config`](/consul/docs/agent/config/config-files#dns_config)
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### Configure WAN address translation
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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:
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- [advertise-wan](/consul/docs/agent/config/cli-flags#_advertise-wan)
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- [translate_wan_addrs](/consul//docs/agent/config/config-files#translate_wan_addrs)
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### Use a custom DNS resolver library
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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.
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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.
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### Enable non-Consul queries
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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.
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### Forward queries to an agent
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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.
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### Query an alternate domain
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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.
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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.
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Consul's DNS response uses the same domain as the query.
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In the following example, the `alt_domain` parameter in the agent configuration is set to `test-domain`, which enables operators to query the domain:
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```shell-session
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$ dig @127.0.0.1 -p 8600 consul.service.test-domain SRV
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;; QUESTION SECTION:
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;consul.service.test-domain. IN SRV
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;; ANSWER SECTION:
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consul.service.test-domain. 0 IN SRV 1 1 8300 machine.node.dc1.test-domain.
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;; ADDITIONAL SECTION:
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machine.node.dc1.test-domain. 0 IN A 127.0.0.1
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machine.node.dc1.test-domain. 0 IN TXT "consul-network-segment="
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```
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#### PTR queries
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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.
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### Caching
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By default, DNS results served by Consul are not cached. Refer to the [DNS Caching tutorial](/consul/tutorials/networking/dns-caching) for instructions on how to enable caching.
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