KubeCon + CloudNativeCon Europe 2021 Virtual

Users want more out of their existing clusters. As demand increases, they would like to increase the size of their clusters by adding more nodes and pods (scaling horizontally). One of the key limitations in doing this is immutability of IP addresses. Providing each additional node and pod an IP, quickly exhausts users’ initial IP allocations. They must resort to optimizing IP addresses in their existing clusters, or pre-emptively over-allocating IP addresses during cluster creation time. With Discontiguous Pod and Node CIDRs, IP addresses become a mutable resource that can be added post-cluster creation thereby helping in the growing the cluster dynamically. Adding support for disjoint CIDRs also allows fitting clusters into fragmented IP spaces, a problem commonly faced by enterprise customers. This talk will describe how GKE solves the problem for customers and the lessons learnt along the way. This talk also proposes ideas on how to solve this natively in Kubernetes.