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Step-by-step tutorials from Red Hat experts to help you get the most out of your Managed OpenShift cluster.
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Adding ROSA IP/subnetting doc #533

Closed thatcherhubbard closed 5 months ago

thatcherhubbard commented 6 months ago

It was easier to close my old PR and just start over on this. I created this doc awhile ago to try to address some questions around ip address and subnet utliziation that have come up, and give customers are resource to guide them through planning their environment.

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thatcherhubbard commented 5 months ago

This is a good catch, and I realize that should also mention and link to the bit in the official docs about the reserved ranges for OVN as well. Thanks!

On Mon, Apr 29, 2024 at 8:57 AM Paul Czarkowski @.***> wrote:

@.**** commented on this pull request.

In content/rosa/ip-addressing-and-subnets/index.md https://github.com/rh-mobb/documentation/pull/533#discussion_r1583329170 :

+ +# VPC and Subnet IP Address Considerations with ROSA + +ROSA clusters can be built to be highly available using the fundamental capability that underlies most HA configurations on AWS: Availability Zones. By spreading the resources of a cluster across three separate (but regionally co-located) datacenters, ROSA users can ensure the cluster continues to run even if an entire AWS AZ goes down. + +This capability comes with a few challenges and considerations around IP addressing that this article will attempt to explain and provide options and best practices around. + +## ROSA and network CIDRs + +Configuring a ROSA cluster requires the provision of three non-overlapping CIDR ranges, as is typical for any Kubernetes installation: + +1. The Machine CIDR range (the range that node IP addresses are assigned from) +1. The Service CIDR range (the range that OpenShift will assign Service IPs from) +1. The Pod CIDR range (the range that OpenShift will assign Pod IPs from) + +The Service and Pod CIDR ranges are typically safe to overlap with other clusters because they are used exclusively for intra-cluster communication.

"However they should never conflict with other non-OCP resources on your network, while they're non-routable, if they overlap with another service elsewhere on the network, they won't be able to route to that service"

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