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Red Hat OpenShift on IBM Cloud(VPC): Worker Nodeの更新によってIPアドレスは変わるかどうか検証してみた

Last updated at Posted at 2020-07-10

1. はじめに

When you create a cluster, you can specify only one existing VPC subnet for each zone. Each worker node that you add in a cluster is deployed with a private IP address from the VPC subnet in that zone. After the worker node is provisioned, the worker node IP address persists after a reboot operation, but the worker node IP address changes after replace and update operations.

な、なにー!?更新をすると、Worker nodeのIPアドレスが変わるかもしれないだと!?
ということで、本当に変わるかどうか、それによってService(type:LoadBalancer)の実体 であるVPC Load Balancerがどのように影響を受けるのかを確認してみた。

2. 更新前情報

Worker NodeのIPアドレスは以下の通り。

  • 10.240.0.4 <-これを更新
  • 10.240.0.5
  • 10.240.64.4 <-これを更新
  • 10.240.64.5
  • 10.240.128.4 <-これを更新
  • 10.240.128.5
image.png image.png

3. 途中経過

image.png image.png

4. 最終状態

IPアドレスは変わった!

  • 10.240.0.4 -> 10.240.0.10
  • 10.240.0.5
  • 10.240.64.4 -> 10.240.64.11
  • 10.240.64.5
  • 10.240.128.4 -> 10.240.128.10
  • 10.240.128.5
image.png

VPC LoadBalancerに登録されているノードも自動的に更新された!(VPC load balancerはあくまでReconciliation Loopの中で管理されており、利用者が手動で変更するものではない)

image.png

5. 残りのWorker Nodeも更新した結果

残りのノードのIPアドレスも変更されて、VPC Load Balancerの割り振り先も変更された。

  • 10.240.0.4 -> 10.240.0.10
  • 10.240.0.5 -> 10.240.0.11
  • 10.240.64.4 -> 10.240.64.11
  • 10.240.64.5 -> 10.240.64.12
  • 10.240.128.4 -> 10.240.128.10
  • 10.240.128.5 -> 10.240.128.11
image.png image.png
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