Skip to main content
Version: 3.28 (latest)

IP reservation

An IP reservation resource (IPReservation) represents a collection of IP addresses that Calico should not use when automatically assigning new IP addresses. It only applies when Calico IPAM is in use.

Sample YAML

kind: IPReservation
name: my-ipreservation-1
- cafe:f00d::/123

IP reservation definition


FieldDescriptionAccepted ValuesSchema
nameThe name of this IPReservation resource. Required.Alphanumeric string with optional ., _, or -.string


FieldDescriptionAccepted ValuesSchemaDefault
reservedCIDRsList of IP addresses and/or networks specified in CIDR notationList of valid IP addresses (v4 or v6) and/or CIDRslist


The implementation of IPReservations is designed to handle reservation of a small number of IP addresses/CIDRs from (generally much larger) IP pools. If a significant portion of an IP pool is reserved (say more than 10%) then Calico may become significantly slower when searching for free IPAM blocks.

Since IPReservations must be consulted for every IPAM assignment request, it's best to have one or two IPReservation resources with multiple addresses per IPReservation resource (rather than having many IPReservation resources), each with one address inside.

If an IPReservation is created after an IP from its range is already in use then the IP is not automatically released back to the pool. The reservation check is only done at auto allocation time.

Calico supports Kubernetes annotations that force the use of specific IP addresses. These annotations override any IPReservations that are in place.

When Windows nodes claim blocks of IPs they automatically assign the first three IPs in each block and the final IP for internal purposes. These assignments cannot be blocked by an IPReservation. However, if a whole IPAM block is reserved with an IPReservation, Windows nodes will not claim such a block.