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RE: Which openshift instances need a public IP

We have an OpenShift cluster that is all internal, for dev purposes.  It consists of a master + 2 nodes, all of which have a private IP.  As long as the three hosts can communicate (are on the same network or can route to one another, AND can resolve each other’s hostnames in DNS) then you’re good.  These three hosts run CentOS 7 Atomic.  A wildcard DNS record points to the IPs of the two nodes, where the routers run, so its a round-robin DNS thing.  Not the most optimal HA set up, but its simple and works well thus far.


Also, we used a regular CentOS 7 host (not Atomic) that’s not part of the cluster that acts as the “utility” server. It has Ansible installed and can ssh to all the cluster hosts in order to fire off the playbooks.


We are just getting started so haven’t set up our production cluster yet. For that, I imagine we’ll need public IPs (assigned to our nodes that are running routers) so that the world can get to our apps. 


So anyway, I *think* the answer to your question is you need public IPs on the openshift nodes that run your routers if the applications are to be publicly accessible.  The blog post here suggests running your router on just the master:  https://tobrunet.ch/articles/dive-into-openshift-v3


…A wildcard DNS entry pointing to the IP address of the master. It is at this master where routers will run to allow for external clients to request application resources running within OpenShift.


From: users-bounces lists openshift redhat com [mailto:users-bounces lists openshift redhat com] On Behalf Of Den Cowboy
Sent: Thursday, December 08, 2016 9:34 AM
To: Frederic Giloux <fgiloux redhat com>
Cc: users lists openshift redhat com
Subject: Re: Which openshift instances need a public IP


Thanks for your reply. Just the main goal we want to obtain is to keep our traffic from pod to pod (using routes, router, dns-wildcard) internal. So performing al this stuf on a private IP. Is that possible?

I just checked this blog: http://dustymabe.com/2016/12/07/installing-an-openshift-origin-cluster-on-fedora-25-atomic-host-part-1/#comment-42901


He is using public ip's + private ip's. Are the privates useful in this case?

We're able to use both and use and we can setup our own dns server but we don't want that our routes are going outside of our cluster. In public and than going back in the cluster. 


So main goal: translations of routes through router should stay in the private network.
Is that possible?



Van: Frederic Giloux <fgiloux redhat com>
Verzonden: donderdag 8 december 2016 13:35:12
Aan: Den Cowboy
CC: users lists openshift redhat com
Onderwerp: Re: Which openshift instances need a public IP


Hi Den,

you may need internet connectivity. Public IPs is not a requirement for that (confer proxy and NAT). Another option is to install OpenShift disconnected. See: https://docs.openshift.com/container-platform/3.3/install_config/install/disconnected_install.html.


An OpenShift Container Platform disconnected installation differs from a regular installation in two primary ways:


Also, editing etc/hosts is not enough. You will require a proper DNS server (dnsmasq for instance) as the containers don't use /etc/hosts of the host for name resolution.





On Thu, Dec 8, 2016 at 1:37 PM, Den Cowboy <dencowboy hotmail com> wrote:



We have our own Registry (like dockerhub) from where we can pull images. (the registry is in the same private network 192.168.25.x).

Now we're trying to install OpenShift (very basic: 1 master + 1 node) on and

We have experience with those installs but than we used public ip's.

We have SSH acces from our master to our node.


But: prereqs: you need ansible on the master, git, docker on master and node, ...
- So initially we need public ip's on our servers to install those prerequisitions?

- Do we need a public IP on every instance when we want to run the playbook? (it failed for resolving something to check ik yum-utils were installed).

- Is this a good solution?: (public IP and private on master and node). Install prereqs and execute playbook. So we have a cluster. After that deleting the public network and reexecuting the playbook with only private ip's (or only a public ip on the master). Will this work?


So as you can see we can use some input in using the setup.
We want that the traffic between our nodes goes internally. So we probably need our own DNS server for hosts, routing, wildcards. (initially we try to cover this in /etc/hosts).


If someone has experience with the setup of OpenShift where the communication over routes (through the router) happends internally (so no public wildcard). Please share some knowledge :).

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Frédéric Giloux
Senior Middleware Consultant

Red Hat GmbH
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