Re: IPAM in Openshift 3.7

Saad_SID · ‎03-19-2020

Theoricaly in K8S it should be PoD level and not CLuster Level , we have a business requirmeents to manage it on a Cluster level .

My question is where I can find solution how Openshift handle it ? and whether two clusters can have Duplicate IP but still seprate in on Cluster level ?

flozano · ‎03-24-2020

Hi Saad,

Could you please provide more context about your question? Managin IP addresses of pods and nodes in OpenShift are unrelated subjects and I am not sure which you you need.

IP addresses for Pods and Services are internal to a cluster, not routable to outside of the cluster, and unrelated to IP addresses of nodes. OpenShift manages those IP addresses internally, as part of an internal SDN, and there is no need to use an external DHCP server. In fact you cannot use one if you want.

Worker nodes (not masters) are also part of the pod and service SDN, but this does not affect their IP addresses as seen by other nodes and machines outside of the cluster.

For your nodes (masters and workers), you can manage their IP addresses normally, and I'm not sure but I think they require stable addresses and hostnames (non-dynamic) because all comunication between masters and nodes are secured using TLS certificates.

Because pod and service IP addresses are internal, there is no issue having multiple clusters that use the same IP addresses for them. Applications from these clusters have to communicate using routes.

Maybe this helps:

https://docs.openshift.com/container-platform/3.7/architecture/networking/sdn.html

Saad_SID · ‎04-14-2020

Thanks Flozano ,

I am clear about PoD /Service from Openshift , actually as i asked we want to use Cluster API's

https://kubernetes.io/docs/tasks/administer-cluster/access-cluster-api/

questino is do Openshift support it on Cluster level or we can use it for each PoD . ALso what i understand from openshift point of view boundary of Cluster API and PoD API is not clear .

Is my query clear for attached URL ? where i can use these API's in OCP ?

@flozano wrote:
Hi Saad,
Could you please provide more context about your question? Managin IP addresses of pods and nodes in OpenShift are unrelated subjects and I am not sure which you you need.
IP addresses for Pods and Services are internal to a cluster, not routable to outside of the cluster, and unrelated to IP addresses of nodes. OpenShift manages those IP addresses internally, as part of an internal SDN, and there is no need to use an external DHCP server. In fact you cannot use one if you want.
Worker nodes (not masters) are also part of the pod and service SDN, but this does not affect their IP addresses as seen by other nodes and machines outside of the cluster.
For your nodes (masters and workers), you can manage their IP addresses normally, and I'm not sure but I think they require stable addresses and hostnames (non-dynamic) because all comunication between masters and nodes are secured using TLS certificates.
Because pod and service IP addresses are internal, there is no issue having multiple clusters that use the same IP addresses for them. Applications from these clusters have to communicate using routes.
Maybe this helps:
https://docs.openshift.com/container-platform/3.7/architecture/networking/sdn.html

@flozano