Configuring IP-in-IP

If your network fabric performs source/destination address checks and drops traffic when those addresses are not recognized, it may be necessary to enable IP-in-IP encapsulation of the inter-workload traffic.

This is often the case for public-cloud environments where you have limited control over the network, and in particular you have no option to set up BGP peering between your Calico nodes and the network routers.

Calico can be configured to use IP-in-IP encapsulation by enabling the IPIP option on the IP pool resource. When enabled, Calico will use IP-in-IP encapsulation when routing packets to workload IPs falling in the IP pool range.

An optional ipipMode field toggles when IP-in-IP is used, see following sections for details.

Configuring IP-in-IP for all inter-workload traffic

With the IP-in-IP ipipMode set to Always, Calico will route using IP-in-IP for all traffic originating from a Calico enabled host to all Calico networked containers and VMs within the IP Pool.

The following calicoctl command will create or modify an IPv4 pool with CIDR 192.168.0.0/16 to use IP-in-IP with mode Always:

calicoctl apply -f - << EOF
apiVersion: projectcalico.org/v3
kind: IPPool
metadata:
  name: ippool-ipip-1
spec:
  cidr: 192.168.0.0/16
  ipipMode: Always
  natOutgoing: true
EOF

Note: The default value for ipipMode is Always, and therefore may be omitted from the request. It is included above for clarity.

Configuring CrossSubnet IP-in-IP

IP-in-IP encapsulation can also be performed selectively, only for traffic crossing subnet boundaries. This provides better performance in AWS multi-AZ deployments, and in general when deploying on networks where pools of nodes with L2 connectivity are connected via a router.

To enable this feature, using an IP-in-IP ipipMode of CrossSubnet.

The following calicoctl command will create or modify an IPv4 pool with CIDR 192.168.0.0/16 to use IP-in-IP with mode CrossSubnet:

calicoctl apply -f - << EOF
apiVersion: projectcalico.org/v3
kind: IPPool
metadata:
  name: ippool-cs-1
spec:
  cidr: 192.168.0.0/16
  ipipMode: CrossSubnet
  natOutgoing: true
EOF

Note: The CrossSubnet mode option requires each Calico node to be configured with the IP address and subnet of the host. However, the subnet configuration was only introduced in Calico v2.1. If any nodes in your deployment were originally created with an older version of Calico, or if you are unsure whether your deployment is configured correctly, follow the steps in Upgrading from pre-v2.1 before enabling CrossSubnet IPIP.

Upgrading from pre-v2.1

If you are planning to use CrossSubnet IPIP, your entire deployment must be running with Calico v2.1 or higher. See releases page for details on the component versions for each release.

Upgrade your deployment to use the latest Calico versions - the process for this will be dependent on your orchestration system (if using one).

Prior to Calico v2.1, the subnet information was not detected and stored on the node configuration. Thus, if you have calico/node instances that were deployed prior to v2.1, the node configuration may need updating to fix the host subnet. The subnet configuration must be set correctly for each node before CrossSubnet IPIP mode is enabled.

You can verify which of your nodes is correctly configured using calicoctl.

calicoctl get nodes --output=wide

An example response follows.

NAME    ASN       IPV4           IPV6
node1   (64512)   10.0.2.15/24
node2   (64512)   10.0.2.10/32

In this example, node1 has the correct subnet information whereas node2 needs to be fixed.

The subnet configuration may be fixed in a few different ways depending on how you have deployed your calico/node containers. This is discussed in the Configuring a Node IP Address and Subnet guide.