kubernetes-the-hard-way/docs/11-pod-network-routes.md

Provisioning Pod Network Routes

Pods scheduled to a node receive an IP address from the node's Pod CIDR range. At this point pods can not communicate with other pods running on different nodes due to missing network routes.

In this lab you will create a route for each worker node that maps the node's Pod CIDR range to the node's internal IP address.

There are other ways to implement the Kubernetes networking model.

The Routing Table (GCloud Only)

In this section you will gather the information required to create routes in the kubernetes-the-hard-way VPC network.

Print the internal IP address and Pod CIDR range for each worker instance:

for instance in worker-0 worker-1 worker-2; do
  gcloud compute instances describe ${instance} \
    --format 'value[separator=" "](networkInterfaces[0].networkIP,metadata.items[0].value)'
done

output

10.240.0.20 10.200.0.0/24
10.240.0.21 10.200.1.0/24
10.240.0.22 10.200.2.0/24

Routes

Create network routes for each worker instance:

gcloud

for i in 0 1 2; do
  gcloud compute routes create kubernetes-route-10-200-${i}-0-24 \
    --network kubernetes-the-hard-way \
    --next-hop-address 10.240.0.2${i} \
    --destination-range 10.200.${i}.0/24
done

az

az network route-table create \
  --name k8s-the-hard-way-route-table

for i in 0 1 2; do
  az network route-table route create \
    --name kubernetes-route-10-200-${i}-0-24 \
    --route-table-name k8s-the-hard-way-route-table \
    --address-prefix 10.200.${i}.0/24 \
    --next-hop-ip-address 10.240.0.2${i} \
    --next-hop-type VirtualAppliance
done

az network vnet subnet update \
  --vnet-name kubernetes-the-hard-way \
  --name kubernetes \
  --route-table k8s-the-hard-way-route-table

List the routes in the kubernetes-the-hard-way VPC network:

gcloud compute routes list --filter "network: kubernetes-the-hard-way"

output

NAME                            NETWORK                  DEST_RANGE     NEXT_HOP                  PRIORITY
default-route-1606ba68df692422  kubernetes-the-hard-way  10.240.0.0/24  kubernetes-the-hard-way   0
default-route-615e3652a8b74e4d  kubernetes-the-hard-way  0.0.0.0/0      default-internet-gateway  1000
kubernetes-route-10-200-0-0-24  kubernetes-the-hard-way  10.200.0.0/24  10.240.0.20               1000
kubernetes-route-10-200-1-0-24  kubernetes-the-hard-way  10.200.1.0/24  10.240.0.21               1000
kubernetes-route-10-200-2-0-24  kubernetes-the-hard-way  10.200.2.0/24  10.240.0.22               1000

Next: Deploying the DNS Cluster Add-on