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Merge pull request #11770 from hashicorp/move-dns-alt-domain-section 

improve location of DNS alt domain docs section
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Jared Kirschner 2021-12-07 15:18:44 -05:00 committed by GitHub
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@ -96,47 +96,6 @@ pairs according to [RFC1464](https://www.ietf.org/rfc/rfc1464.txt).
Alternatively, the TXT record will only include the node's metadata value when the
node's metadata key starts with `rfc1035-`.
## Alternative 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`](/docs/agent/options#domain) parameter.
In some instances, Consul may need to respond to queries in more than one domain,
such as during a DNS migration or to distinguish between internal and external queries.
Consul versions 1.5.2+ can be configured to respond to DNS queries on an alternative domain
through the [`alt_domain`](/docs/agent/options#alt_domain) agent configuration
option. As of Consul versions 1.11.0+, Consul's DNS response will use the same domain as was used in the query;
in prior versions, the response may use the primary [`domain`](/docs/agent/options#domain) no matter which
domain was used in the query.
In the following example, the `alt_domain` parameter is set to `test-domain`:
```hcl
alt_domain = "test-domain"
```
```shell-session
$ dig @127.0.0.1 -p 8600 consul.service.test-domain SRV
```
The following responses are returned:
```
;; QUESTION SECTION:
;consul.service.test-domain. IN SRV
;; ANSWER SECTION:
consul.service.test-domain. 0 IN SRV 1 1 8300 machine.node.dc1.test-domain.
;; ADDITIONAL SECTION:
machine.node.dc1.test-domain. 0 IN A 127.0.0.1
machine.node.dc1.test-domain. 0 IN TXT "consul-network-segment="
```
-> **PTR queries:** Responses to PTR queries (`<ip>.in-addr.arpa.`) will always use the
[primary domain](/docs/agent/options#domain) (not the alternative domain),
as there is no way for the query to specify a domain.
## Service Lookups
A service lookup is used to query for service providers. Service queries support
@ -319,6 +278,47 @@ without setting the truncate bit. This is to prevent a redundant lookup over
TCP that generates additional load. If the lookup is done over TCP, the results
are not truncated.
## Alternative 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`](/docs/agent/options#domain) parameter.
In some instances, Consul may need to respond to queries in more than one domain,
such as during a DNS migration or to distinguish between internal and external queries.
Consul versions 1.5.2+ can be configured to respond to DNS queries on an alternative domain
through the [`alt_domain`](/docs/agent/options#alt_domain) agent configuration
option. As of Consul versions 1.11.0+, Consul's DNS response will use the same domain as was used in the query;
in prior versions, the response may use the primary [`domain`](/docs/agent/options#domain) no matter which
domain was used in the query.
In the following example, the `alt_domain` parameter is set to `test-domain`:
```hcl
alt_domain = "test-domain"
```
```shell-session
$ dig @127.0.0.1 -p 8600 consul.service.test-domain SRV
```
The following responses are returned:
```
;; QUESTION SECTION:
;consul.service.test-domain. IN SRV
;; ANSWER SECTION:
consul.service.test-domain. 0 IN SRV 1 1 8300 machine.node.dc1.test-domain.
;; ADDITIONAL SECTION:
machine.node.dc1.test-domain. 0 IN A 127.0.0.1
machine.node.dc1.test-domain. 0 IN TXT "consul-network-segment="
```
-> **PTR queries:** Responses to PTR queries (`<ip>.in-addr.arpa.`) will always use the
[primary domain](/docs/agent/options#domain) (not the alternative domain),
as there is no way for the query to specify a domain.
## Caching
By default, all DNS results served by Consul set a 0 TTL value. This disables