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](https://cloud.google.com/compute/docs/vpc/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](https://kubernetes.io/docs/concepts/cluster-administration/networking/#how-to-achieve-this) to implement the Kubernetes networking model.

## The Routing Table

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:

#### Linux & OS X
```
for instance in worker-0 worker-1 worker-2; do
  gcloud compute instances describe ${instance} \
    --format '(networkInterfaces[0].networkIP,metadata.items[0].value)'
done
```

#### Windows
```
@('worker-0','worker-1','worker-2') | ForEach-Object {
  gcloud compute instances describe $_ `
  --format "value[separator=' '](networkInterfaces[0].networkIP,metadata.items[0].value)"
}
```
> 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:

#### Linux & OS X
```
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
```

#### Windows
```
@(0, 1, 2) | ForEach-Object {
  gcloud compute routes create kubernetes-route-10-200-${_}-0-24 `
    --network kubernetes-the-hard-way `
    --next-hop-address 10.240.0.2${_} `
    --destination-range 10.200.${_}.0/24
}
```

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-77bcc6bee33b5535  kubernetes-the-hard-way  10.240.0.0/24                            1000
default-route-b11fc914b626974d  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](12-dns-addon.md)