IP Pool Resource (IPPool)

An IP pool resource (IPPool) represents a collection of IP addresses from which Calico expects endpoint IPs to be assigned.

For calicoctl commands that specify a resource type on the CLI, the following aliases are supported (all case insensitive): ippool, ippools, ipp, ipps, pool, pools.

Sample YAML

apiVersion: projectcalico.org/v3
kind: IPPool
  name: my.ippool-1
  ipipMode: CrossSubnet
  natOutgoing: true
  disabled: false

IP Pool Definition


Field Description Accepted Values Schema
name The name of this IPPool resource. Required. Alphanumeric string with optional ., _, or -. string


Field Description Accepted Values Schema Default
cidr IP range to use for this pool. A valid IPv4 or IPv6 CIDR. Subnet length must be at least big enough to fit a single block (by default /26 for IPv4 or /122 for IPv6). Must not overlap with the Link Local range or fe80::/10. string  
blockSize The CIDR size of allocation blocks used by this pool. Blocks are allocated on demand to hosts and are used to aggregate routes. The value can only be set when the pool is created. 20 to 32 (inclusive) for IPv4 and 116 to 128 (inclusive) for IPv6 int 26 for IPv4 pools and 122 for IPv6 pools.
ipipMode The IPIP mode defining when IPIP will be used. Always, CrossSubnet, Never string Never
natOutgoing When enabled, packets sent from Calico networked containers in this pool to destinations outside of this pool will be masqueraded. true, false boolean false
disabled When set to true, Calico IPAM will not assign addresses from this pool. true, false boolean false

Important: Do not use a custom blockSize until all Calico components have been updated to a version that supports it (at least v3.3.0). Older versions of components do not understand the field so they may corrupt the IP pool by creating blocks of incorrect size.


Routing of packets using IP-in-IP will be used when the destination IP address is in an IP Pool that has IPIP enabled. In addition, if the ipipMode is set to CrossSubnet, Calico will only route using IP-in-IP if the IP address of the destination node is in a different subnet. The subnet of each node is configured on the node resource (which may be automatically determined when running the calico/node service).

For details on configuring IP-in-IP on your deployment, please read the Configuring IP-in-IP guide.

Note: Setting natOutgoing is recommended on any IP Pool with ipip enabled. When ipip is enabled without natOutgoing routing between Workloads and Hosts running Calico is asymmetric and may cause traffic to be filtered due to RPF checks failing.

Block Sizes

The default block sizes of 26 for IPv4 and 122 for IPv6 provide blocks of 64 addresses. This allows addresses to be allocated in groups to workloads running on the same host. By grouping addresses, fewer routes need to be exchanged between hosts and to other BGP peers. If a host allocates all of the addresses in a block then it will be allocated an additional block. If there are no more blocks available then the host can take addresses from blocks allocated to other hosts. Specific routes are added for the borrowed addresses which has an impact on route table size.

Increasing the block size from the default (e.g., using 24 for IPv4 to give 256 addresses per block) means fewer blocks per host, and potentially fewer routes. But try to ensure that there are at least as many blocks in the pool as there are hosts.

Reducing the block size from the default (e.g., using 28 for IPv4 to give 16 addresses per block) means more blocks per host and therefore potentially more routes. This can be beneficial if it allows the blocks to be more fairly distributed amongst the hosts.

Supported operations

Datastore type Create/Delete Update Get/List Notes
etcdv3 Yes Yes Yes  
Kubernetes API server Yes Yes Yes