mirror of
https://github.com/coredns/coredns.git
synced 2025-10-31 10:13:14 -04:00
131 lines
2.9 KiB
Groff
131 lines
2.9 KiB
Groff
.\" Generated by Mmark Markdown Processer - mmark.miek.nl
|
|
.TH "COREDNS-K8S_EXTERNAL" 7 "August 2020" "CoreDNS" "CoreDNS Plugins"
|
|
|
|
.SH "NAME"
|
|
.PP
|
|
\fIk8s_external\fP - resolves load balancer and external IPs from outside Kubernetes clusters.
|
|
|
|
.SH "DESCRIPTION"
|
|
.PP
|
|
This plugin allows an additional zone to resolve the external IP address(es) of a Kubernetes
|
|
service. This plugin is only useful if the \fIkubernetes\fP plugin is also loaded.
|
|
|
|
.PP
|
|
The plugin uses an external zone to resolve in-cluster IP addresses. It only handles queries for A,
|
|
AAAA and SRV records; all others result in NODATA responses. To make it a proper DNS zone, it handles
|
|
SOA and NS queries for the apex of the zone.
|
|
|
|
.PP
|
|
By default the apex of the zone will look like the following (assuming the zone used is \fB\fCexample.org\fR):
|
|
|
|
.PP
|
|
.RS
|
|
|
|
.nf
|
|
example.org. 5 IN SOA ns1.dns.example.org. hostmaster.example.org. (
|
|
12345 ; serial
|
|
14400 ; refresh (4 hours)
|
|
3600 ; retry (1 hour)
|
|
604800 ; expire (1 week)
|
|
5 ; minimum (4 hours)
|
|
)
|
|
example.org 5 IN NS ns1.dns.example.org.
|
|
|
|
ns1.dns.example.org. 5 IN A ....
|
|
ns1.dns.example.org. 5 IN AAAA ....
|
|
|
|
.fi
|
|
.RE
|
|
|
|
.PP
|
|
Note that we use the \fB\fCdns\fR subdomain for the records DNS needs (see the \fB\fCapex\fR directive). Also
|
|
note the SOA's serial number is static. The IP addresses of the nameserver records are those of the
|
|
CoreDNS service.
|
|
|
|
.PP
|
|
The \fIk8s_external\fP plugin handles the subdomain \fB\fCdns\fR and the apex of the zone itself; all other
|
|
queries are resolved to addresses in the cluster.
|
|
|
|
.SH "SYNTAX"
|
|
.PP
|
|
.RS
|
|
|
|
.nf
|
|
k8s\_external [ZONE...]
|
|
|
|
.fi
|
|
.RE
|
|
|
|
.IP \(bu 4
|
|
\fBZONES\fP zones \fIk8s_external\fP should be authoritative for.
|
|
|
|
|
|
.PP
|
|
If you want to change the apex domain or use a different TTL for the returned records you can use
|
|
this extended syntax.
|
|
|
|
.PP
|
|
.RS
|
|
|
|
.nf
|
|
k8s\_external [ZONE...] {
|
|
apex APEX
|
|
ttl TTL
|
|
}
|
|
|
|
.fi
|
|
.RE
|
|
|
|
.IP \(bu 4
|
|
\fBAPEX\fP is the name (DNS label) to use for the apex records; it defaults to \fB\fCdns\fR.
|
|
.IP \(bu 4
|
|
\fB\fCttl\fR allows you to set a custom \fBTTL\fP for responses. The default is 5 (seconds).
|
|
|
|
|
|
.SH "EXAMPLES"
|
|
.PP
|
|
Enable names under \fB\fCexample.org\fR to be resolved to in-cluster DNS addresses.
|
|
|
|
.PP
|
|
.RS
|
|
|
|
.nf
|
|
\&. {
|
|
kubernetes cluster.local
|
|
k8s\_external example.org
|
|
}
|
|
|
|
.fi
|
|
.RE
|
|
|
|
.PP
|
|
With the Corefile above, the following Service will get an \fB\fCA\fR record for \fB\fCtest.default.example.org\fR with the IP address \fB\fC192.168.200.123\fR.
|
|
|
|
.PP
|
|
.RS
|
|
|
|
.nf
|
|
apiVersion: v1
|
|
kind: Service
|
|
metadata:
|
|
name: test
|
|
namespace: default
|
|
spec:
|
|
clusterIP: None
|
|
externalIPs:
|
|
\- 192.168.200.123
|
|
type: ClusterIP
|
|
|
|
.fi
|
|
.RE
|
|
|
|
.PP
|
|
For some background see resolve external IP address
|
|
\[la]https://github.com/kubernetes/dns/issues/242\[ra].
|
|
And A records for services with Load Balancer IP
|
|
\[la]https://github.com/coredns/coredns/issues/1851\[ra].
|
|
|
|
.PP
|
|
PTR queries for the reverse zone is not supported.
|
|
|