Hi,
1. when you setup your cluster, you will have some node that running a
router pod,and  you need have a subdomain for your cluster, for example,
you cluster will use product.example.com, so you need the DNS server
setting forward the request with this DNS name prefix product.example.com to
the router node.

2. Assume create a project named test, and  you deploy an app to the
openshift cluster, you need create a route [1] for external access,  after
you do that, the url you can be access is by test.product.example.com.
 when you access the your app from outside, the general flow will be:

1. public dns server redirect you to your DNS server
2. Your dns server forward your request to one of the  node which have
openshift router pod deployed
3. the router pod(it's running haproxy by default) will forward the request
to the running pods

Hope this can help you. :)


[1]https://docs.openshift.org/latest/dev_guide/routes.html

Regards,
Haoran Wang

OpenShift QE
IRC: haowang
Raycom office - Red Hat China
Direct: +86 10  <+86%2010%206562%207492>65339430(ext-8389430)


On Thu, Jul 13, 2017 at 5:47 PM, bmeng <bm...@redhat.com> wrote:

> AFAIK, the kube-dns resolve the service-names inside the cluster.
>
> The dns server required by OpenShift gives the applications external
> accessibility.
>
> With the dns resolution and the route you created for your application,
> you can access your web application anywhere.
>
> On 07/13/2017 05:09 PM, Yu Wei wrote:
>
> Hi,
>
> I'm learning OpenShift by setting up cluster with VMs.
>
> From the document, some content about DNS is as below,
>
> *OpenShift Origin requires a fully functional DNS server in the
> environment. This is ideally a separate host running DNS software and can
> provide name resolution to hosts and containers running on the platform.*
>
>
> Why does separate dns server need? Could kub-dns be used?
>
>
> Thanks,
>
> Jared, (韦煜)
> Software developer
> Interested in open source software, big data, Linux
>
>
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