IP pool

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
  nodeSelector: all()

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 mode defining when IPIP will be used. Cannot be set at the same time as vxlanMode. Always, CrossSubnet, Never string Never
vxlanMode The mode defining when VXLAN will be used. Cannot be set at the same time as ipipMode. Always, 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
nodeSelector Selects the nodes that Calico IPAM should assign addresses from this pool to.   selector all()

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 refer to Configuring IP-in-IP.

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.


Similarly to IP-in-IP, if vxlanMode is set to Always, VXLAN encapsulation will be used if the IP of the destination is within the pool.

CrossSubnet mode is not supported with VXLAN in this release.

Note: As with IP-in-IP, setting natOutgoing is recommended on any IP Pool with VXLAN enabled.

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.

Node Selector

A label selector is an expression which either matches or does not match a resource based on its labels.

Calico label selectors support a number of syntactic primitives. Each of the following primitive expressions can be combined using the logical operator &&.

Syntax Meaning
all() Match all resources.
k == ‘v’ Matches any resource with the label ‘k’ and value ‘v’.
k != ‘v’ Matches any resource with the label ‘k’ and value that is not ‘v’.
has(k) Matches any resource with label ‘k’, independent of value.
!has(k) Matches any resource that does not have label ‘k’
k in { ‘v1’, ‘v2’ } Matches any resource with label ‘k’ and value in the given set
k not in { ‘v1’, ‘v2’ } Matches any resource without label ‘k’ or any with label ‘k’ and value not in the given set
k contains ‘s’ Matches any resource with label ‘k’ and value containing the substring ‘s’
k starts with ‘s’ Matches any resource with label ‘k’ and value starting with the substring ‘s’
k ends with ‘s’ Matches any resource with label ‘k’ and value ending with the substring ‘s’

For details on configuring IP pool node selectors, please read the Assigning IP addresses based on topology guide..

Note: The pool’s disabled field takes higher precedence than nodeSelector. This means that Calico IPAM will not allocate any IPs from a disabled pool even if it selects the node that it is on.

Supported operations

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