Frequently asked questions

Why use Calico?

The problem Calico tries to solve is the networking of workloads (VMs, containers, etc) in a high scale environment. Existing L2-based methods for solving this problem have problems at high scale. Compared to these, we think Calico is more scalable, simpler, and more flexible. We think you should look into it if you have more than a handful of nodes on a single site.

Calico also provides a rich network security model that allows operators and developers to declare intent-based network security policy that is automatically rendered into distributed firewall rules across a cluster of containers, VMs, and/or servers.

For a more detailed discussion of this topic, see our blog post at Why Calico?.

Does Calico work with IPv6?

Yes! Calico’s core components support IPv6 out of the box. However, not all orchestrators that we integrate with support IPv6 yet.

Why does my container have a route to 169.254.1.1?

In a Calico network, each host acts as a gateway router for the workloads that it hosts. In container deployments, Calico uses 169.254.1.1 as the address for the Calico router. By using a link-local address, Calico saves precious IP addresses and avoids burdening the user with configuring a suitable address.

While the routing table may look a little odd to someone who is used to configuring LAN networking, using explicit routes rather than subnet-local gateways is fairly common in WAN networking.

Why isn’t Calico working with a containerized Kubelet?

Calico hosted install places the necessary CNI binaries and config on each Kubernetes node in a directory on the host as specified in the manifest. By default it places binaries in /opt/cni/bin and config /etc/cni/net.d.

When running the kubelet as a container using hyperkube, you need to make sure that the containerized kubelet can see the CNI network plugins and config that have been installed by mounting them into the kubelet container.

For example add the following arguments to the kubelet-wrapper service:

  1. --volume /etc/cni/net.d:/etc/cni/net.d \
  2. --volume /opt/cni/bin:/opt/cni/bin \

Without the above volume mounts, the kubelet will not call the Calico CNI binaries, and so Calico workload endpoints will not be created, and Calico policy will not be enforced.

How do I view Calico CNI logs?

The Calico CNI plugin emits logs to stderr, which are then logged out by the kubelet. Where these logs end up depend on how your kubelet is configured. For deployments using systemd, you can do this via journalctl.

The log level can be configured via the CNI network configuration file, by changing the value of the key log_level. See Configuring the Calico CNI plugins for more information.

CNI plugin logs can also be found in /var/log/calico/cni.

How do I configure the pod IP range?

When using Calico IPAM, IP addresses are assigned from IP Pools.

By default, all enabled IP pools are used. However, you can specify which IP pools to use for IP address management in the CNI network config, or on a per-pod basis using Kubernetes annotations.

How do I assign a specific IP address to a pod?

For most use cases it’s not necessary to assign specific IP addresses to a Kubernetes pod and it’s recommended to use Kubernetes services instead. However, if you do need to assign a particular address to a pod, Calico provides two ways of doing this:

  • You can request an IP that is available in Calico IPAM using the cni.projectcalico.org/ipAddrs annotation.
  • You can request an IP using the cni.projectcalico.org/ipAddrsNoIpam annotation. Note that this annotation bypasses the configured IPAM plugin, and thus in most cases it is recommended to use the above annotation.

See the Requesting a specific IP address section in the CNI plugin reference documentation for more details.

Why can’t I see the 169.254.1.1 address mentioned above on my host?

Calico tries hard to avoid interfering with any other configuration on the host. Rather than adding the gateway address to the host side of each workload interface, Calico sets the proxy_arp flag on the interface. This makes the host behave like a gateway, responding to ARPs for 169.254.1.1 without having to actually allocate the IP address to the interface.

Why do all cali* interfaces have the MAC address ee:ee:ee:ee:ee:ee?

In some setups the kernel is unable to generate a persistent MAC address and so Calico assigns a MAC address itself. Since Calico uses point-to-point routed interfaces, traffic does not reach the data link layer so the MAC Address is never used and can therefore be the same for all the cali* interfaces.

Can I prevent my Kubernetes pods from initiating outgoing connections?

Yes! The Kubernetes NetworkPolicy API added support for egress policies in v1.8. You can also use calicoctl to configure egress policy to prevent Kubernetes pods from initiating outgoing connections based on the full set of supported Calico policy primitives including labels, Kubernetes namespaces, CIDRs, and ports.

I’ve heard Calico uses proxy ARP, doesn’t proxy ARP cause a lot of problems?

It can, but not in the way that Calico uses it.

In container deployments, Calico only uses proxy ARP for resolving the 169.254.1.1 address. The routing table inside the container ensures that all traffic goes via the 169.254.1.1 gateway so that is the only IP that will be ARPed by the container.

Is Calico compliant with PCI/DSS requirements?

PCI certification applies to the whole end-to-end system, of which Calico would be a part. We understand that most current solutions use VLANs, but after studying the PCI requirements documents, we believe that Calico does meet those requirements and that nothing in the documents mandates the use of VLANs.

How do I enable IP-in-IP and NAT outgoing on an IP pool?

  1. Retrieve current IP pool config.

    1. calicoctl get ipPool --export -o yaml > pool.yaml

  2. Modify IP pool config.

    Modify the pool’s spec to enable IP-in-IP and NAT outgoing. (See IP pools for other settings that can be edited.)

    1. - apiVersion: projectcalico.org/v3
    2.   kind: IPPool
    3.   metadata:
    4.    name: ippool-1
    5.   spec:
    6.     cidr: 192.168.0.0/16
    7.     ipipMode: Always
    8.     natOutgoing: true

  3. Load the modified file.

    1. calicoctl replace -f pool.yaml

How does Calico maintain saved state?

State is saved in a few places in a Calico deployment, depending on whether it’s global or local state.

Local state is state that belongs on a single compute host, associated with a single running Felix instance (things like kernel routes, tap devices etc.). Local state is entirely stored by the Linux kernel on the host, with Felix storing it only as a temporary mirror. This makes Felix effectively stateless, with the kernel acting as a backing data store on one side and etcd as a data source on the other.

If Felix is restarted, it learns current local state by interrogating the kernel at start up. It then reads from etcd all the local state which it should have, and updates the kernel to match. This approach has strong resiliency benefits, in that if Felix restarts you don’t suddenly lose access to your VMs or containers. As long as the Linux kernel is running, you’ve still got full functionality.

The bulk of global state is mastered in whatever component hosts the plugin.

  • In the case of OpenStack, this means a Neutron database. Our OpenStack plugin (more strictly a Neutron ML2 driver) queries the Neutron database to find out state about the entire deployment. That state is then reflected to etcd and so to Felix.
  • In certain cases, etcd itself contains the master copy of the data. This is because some Docker deployments have an etcd cluster that has the required resiliency characteristics, used to store all system configuration and so etcd is configured so as to be a suitable store for critical data.
  • In other orchestration systems, it may be stored in distributed databases, either owned directly by the plugin or by the orchestrator itself.

The only other state storage in a Calico network is in the BGP sessions, which approximate a distributed database of routes. This BGP state is simply a replicated copy of the per-host routes configured by Felix based on the global state provided by the orchestrator.

This makes the Calico design very simple, because we store very little state. All of our components can be shut down and restarted without risk, because they resynchronize state as necessary. This makes modeling their behavior extremely simple, reducing the complexity of bugs.

I heard Calico is suggesting layer 2: I thought you were layer 3! What’s happening?

It’s important to distinguish what Calico provides to the workloads hosted in a data center (a purely layer 3 network) with what the Calico project recommends operators use to build their underlying network fabric.

Calico’s core principle is that applications and workloads overwhelmingly need only IP connectivity to communicate. For this reason we build an IP-forwarded network to connect the tenant applications and workloads to each other and the broader world.

However, the underlying physical fabric obviously needs to be set up too. Here, Calico has discussed how both a layer 2 (see here) or a layer 3 (see here) fabric could be integrated with Calico. This is one of the great strengths of the Calico model: it allows the infrastructure to be decoupled from what we show to the tenant applications and workloads.

We have some thoughts on different interconnect approaches (as noted above), but just because we say that there are layer 2 and layer 3 ways of building the fabric, and that those decisions may have an impact on route scale, does not mean that Calico is “going back to Ethernet” or that we’re recommending layer 2 for tenant applications. In all cases we forward on IP packets, no matter what architecture is used to build the fabric.

How do I control policy/connectivity without virtual/physical firewalls?

Calico provides an extremely rich security policy model, applying policy at the first and last hop of the routed traffic within the Calico network (the source and destination compute hosts).

This model is substantially more robust to failure than a centralized firewall-based model. In particular, the Calico approach has no single point of failure: if the device enforcing the firewall has failed then so has one of the workloads involved in the traffic (because the firewall is enforced by the compute host).

This model is also extremely amenable to scaling out. Because we have a central repository of policy configuration, but apply it at the edges of the network (the hosts) where it is needed, we automatically ensure that the rules match the topology of the data center. This allows easy scaling out, and gives us all the advantages of a single firewall (one place to manage the rules), but none of the disadvantages (single points of failure, state sharing, hairpinning of traffic, etc.).

Lastly, we decouple the reachability of nodes and the policy applied to them. We use BGP to distribute the topology of the network, telling every node how to get to every endpoint in case two endpoints need to communicate. We use policy to decide if those two nodes should communicate, and if so, how. If policy changes and two endpoints should now communicate, where before they shouldn’t have, all we have to do is update policy: the reachability information does not change. If later they should be denied the ability to communicate, the policy is updated again, and again the reachability doesn’t have to change.

How does Calico interact with the Neutron API?

Calico’s interpretation of Neutron API calls goes into extensive detail about how various Neutron API calls translate into Calico actions.

Why isn’t the -p flag on docker run working as expected?

The -p flag tells Docker to set up port mapping to connect a port on the Docker host to a port on your container via the docker0 bridge.

If a host’s containers are connected to the docker0 bridge interface, Calico would be unable to enforce security rules between workloads on the same host; all containers on the bridge would be able to communicate with one other.

Can Calico containers use any IP address within a pool, even subnet network/broadcast addresses?

Yes! Calico is fully routed, so all IP address within a Calico pool are usable as private IP addresses to assign to a workload. This means addresses commonly reserved in a L2 subnet, such as IPv4 addresses ending in .0 or .255, are perfectly okay to use.

How do I get network traffic into and out of my Calico cluster?

The recommended way to get traffic to/from your Calico network is by peering to your existing data center L3 routers using BGP and by assigning globally routable IPs (public IPs) to containers that need to be accessed from the internet. This allows incoming traffic to be routed directly to your containers without the need for NAT. This flat L3 approach delivers exceptional network scalability and performance.

A common scenario is for your container hosts to be on their own isolated layer 2 network, like a rack in your server room or an entire data center. Access to that network is via a router, which also is the default router for all the container hosts.

If this describes your infrastructure, [Configure outgoing NAT](/calico/3.25/networking/configuring/workloads-outside-cluster explains in more detail what to do. Otherwise, if you have a layer 3 (IP) fabric, then there are detailed datacenter networking recommendations given in Calico over IP fabrics. We’d also encourage you to get in touch to discuss your environment.

How can I enable NAT for outgoing traffic from containers with private IP addresses?

If you want to allow containers with private IP addresses to be able to access the internet then you can use your data center’s existing outbound NAT capabilities (typically provided by the data center’s border routers).

Alternatively you can use Calico’s built in outbound NAT capability by enabling it on any Calico IP pool. In this case Calico will perform outbound NAT locally on the compute node on which each container is hosted.

  1. cat <<EOF | calicoctl apply -f -
  2. apiVersion: projectcalico.org/v3
  3. kind: IPPool
  4. metadata:
  5.   name: ippool-1
  6. spec:
  7.   cidr: <CIDR>
  8.   natOutgoing: true
  9. EOF

Where <CIDR> is the CIDR of your IP pool, for example 192.168.0.0/16.

Remember: the security profile for the container will need to allow traffic to the internet as well. Refer to the appropriate guide for your orchestration system for details on how to configure policy.

How can I enable NAT for incoming traffic to containers with private IP addresses?

As discussed, the recommended way to get traffic to containers that need to be accessed from the internet is to give them public IP addresses and to configure Calico to peer with the data center’s existing L3 routers.

In cases where this is not possible then you can configure incoming NAT (also known as DNAT) on your data centers existing border routers. Alternatively you can configure incoming NAT with port mapping on the host on which the container is running on.

  1. Create a new chain called expose-ports to hold the NAT rules.

    1. iptables -t nat -N expose-ports

  2. Jump to that chain from the OUTPUT and PREROUTING chains.

    1. iptables -t nat -A OUTPUT -j expose-ports
    2. iptables -t nat -A PREROUTING -j expose-ports

    Frequently asked questions - 图1tip

    The OUTPUT chain is hit by traffic originating on the host itself; the PREROUTING chain is hit by traffic coming from elsewhere.

  3. For each port you want to expose, add a rule to the expose-ports chain, replacing <PUBLIC_IP> with the host IP that you want to use to expose the port and <PUBLIC_PORT> with the host port.

    1. iptables -t nat -A expose-ports -p tcp --destination <PUBLIC_IP> \
    2. --dport <PUBLIC_PORT> -j DNAT  --to <CALICO_IP>:<SERVICE_PORT>

For example, you have a container to which you’ve assigned the CALICO_IP of 192.168.7.4, and you have NGINX running on port 8080 inside the container. If you want to expose this service on port 80 and your host has IP 192.0.2.1, then you could run the following commands:

  1. iptables -t nat -N expose-ports
  2. iptables -t nat -A OUTPUT -j expose-ports
  3. iptables -t nat -A PREROUTING -j expose-ports
  5. iptables -t nat -A expose-ports -p tcp --destination 192.0.2.1 --dport 80 -j DNAT --to 192.168.7.4:8080

The commands will need to be run each time the host is restarted.

Remember: the security profile for the container will need to allow traffic to the exposed port as well. Refer to the appropriate guide for your orchestration system for details on how to configure policy.

Can I run Calico in a public cloud environment?

Yes. If you are running in a public cloud that doesn’t allow either L3 peering or L2 connectivity between Calico hosts then you can enable IP-in-IP in your Calico IP pool:

  1. cat <<EOF | calicoctl apply -f -
  2. apiVersion: projectcalico.org/v3
  3. kind: IPPool
  4. metadata:
  5.   name: ippool-1
  6. spec:
  7.   cidr: <CIDR>
  8.   ipipMode: Always
  9.   natOutgoing: true
  10. EOF

Calico will then route traffic between Calico hosts using IP-in-IP.

For best performance in AWS, you can disable Source/Destination Check instead of using IP-in-IP or VXLAN; but only if all your instances are in the same subnet of your VPC. The setting must be Disable for the EC2 instance(s) to process traffic not matching the host interface IP address. This is also applicable if your cluster is spread across multiple subnets. If your cluster traffic crosses subnets, set ipipMode (or vxlanMode) to CrossSubnet to reduce the encapsulation overhead. Check configuring overlay networking for the details.

You can disable Source/Destination Check using Felix configuration, the AWS CLI, or the EC2 console. For example, using the AWS CLI:

  1. aws ec2 modify-instance-attribute --instance-id <INSTANCE_ID> --source-dest-check "{\"Value\": false}"
  3. cat <<EOF | calicoctl apply -f -
  4. apiVersion: projectcalico.org/v3
  5. kind: IPPool
  6. metadata:
  7.   name: ippool-2
  8. spec:
  9.   cidr: <CIDR>
  10.   natOutgoing: true
  11. EOF

On AWS with IP-in-IP, why do I see no connectivity between workloads or only see connectivity if I ping in both directions?

By default, AWS security groups block incoming IP-in-IP traffic.

However, if an instance has recently sent some IP-in-IP traffic out when it receives some incoming IP-in-IP traffic, then AWS sees that as a response to an outgoing connection and it allows the incoming traffic. This leads to some very confusing behavior where traffic can be blocked and then suddenly start working!

To resolve the issue, add a rule to your security groups that allows inbound and outbound IP-in-IP traffic (IP protocol number 4) between your hosts.

In Calico for OpenStack, why can’t a VM ping its default gateway?

The concept of default gateway makes sense with OpenStack networking drivers that simulate direct layer 2 (Ethernet) connectivity between VMs in the same Neutron network. With that kind of simulation,

  • When a VM sends to another VM in the same network, there is no routing at all, from the VM point of view. (Of course there may be routing in the underlay network, because compute hosts may be on different subnets.)

  • When a VM sends to something outside its own network, it goes - by simulated layer 2 - to the default gateway first, and then is routed to wherever it is addressed to.

However OpenStack also allows drivers, including Calico, that use routing between the VMs of a Neutron network. With Calico specifically, any packet sent by a VM is layer-2-terminated and IP-routed by the VM’s compute host, whether the VM is sending to another VM in the same network, or to anywhere else. So Calico doesn’t need the “default gateway” concept, and it doesn’t really make any sense with Calico. If a VM thinks that “my default gateway is the first hop at which the packets I send can be IP-routed”, and in any way relies on that, that will be wrong, with Calico networking.

Now, with all that said, for detailed technical reasons to do with the DHCP server (dnsmasq), Calico does actually configure the default gateway IP - i.e. bind it to a Linux network interface - on every compute host with at least one VM in the relevant Neutron network; and that is one of the ingredients needed, in Linux, for a VM to be able to ping that IP.

The reason why it still isn’t possible for a VM to ping that IP, is that Calico by default configures iptables rules to block almost all communication to its own host - because in general, of course, a workload should not be able to access and possibly compromise its host. There are a few pinholes here, e.g. for DHCP, but those do not include ping (ICMP Echo). If you start running a command like watch 'sudo iptables-save -c | grep DROP' on a compute host, and then try pinging the default gateway IP from a VM on that host, you will see the DROP count increasing as each ping packet is sent and blocked.

This behaviour is controlled by a config parameter named DefaultEndpointToHostAction, whose default is DROP. For the sake of demonstration, you can change this by adding DefaultEndpointToHostAction = RETURN to /etc/calico/felix.cfg, then use sudo systemctl restart calico-felix to restart Felix, and then you will observe that a VM on that host can ping its default gateway. However we do not recommend routinely operating with DefaultEndpointToHostAction = RETURN, because that potentially allows a malicious VM to compromise its host.

In summary, then, there are two points behind why a VM cannot normally ping its default gateway, with Calico.

  1. The default gateway concept just doesn’t really fit, and isn’t needed, given how Calico routes everything at the compute node - which is a fundamental aspect of Calico networking for OpenStack.

  2. Calico’s iptables rules generally do not allow a VM to contact its host.

Can Calico do IP multicast?

Calico is a routed L3 network where each pod gets a /32. There’s no broadcast domain for pods. That means that multicast doesn’t just work as a side effect of broadcast. To get multicast to work, the host needs to act as a multicast gateway of some kind. Calico’s architecture was designed to extend to cover that case but it’s not part of the product as yet.