I am attempting to build a Kubernetes cluster on Google Container Engine where its pods do requests to the internet (incoming or egress traffic). These outgoing connections must be limited to a static IP or limited to a range of them.
You can opt to https://github.com/doitintl/kubeIP and avoid configuring with NAT
The external IP address is the IP address of the node machines in the GKE cluster. You can specify static IP address to these node vms from the VPC Network => External IP addresses.
A more complex option would be to create a NAT gateway on a separate VM and then route all the traffic from Kubernetes nodes through it.