Reserved Network Resources

CIDR blocks in Shared Address Space

The Shared Address Space, with IP range 100.64.0.0/10, was implemented to connect customer-premises equipment to the core routers of Internet service providers.

To allocate IP addresses to the management interfaces and ILOMs (Oracle Integrated Lights Out Manager) of hardware components, two CIDR blocks are reserved for internal use: 100.96.0.0/23 and 100.96.2.0/23.

CIDR blocks in Class E address range

Under the classful network addressing architecture, Class E is the part of the 32-bit IPv4 address space ranging from 240.0.0.0 to 255.255.255.255. At the time, it was reserved for future use, so it can't be used on the public Internet.

To accommodate the addressing requirements of all infrastructure networking over the physical 100-Gbit connections, the entire 253.255.0.0/16 subnet is reserved. It is further subdivided into multiple CIDR blocks to group IP addresses by network function or type.

The various CIDR blocks within the 253.255.0.0/16 range are used to allocate IP addresses for the Kubernetes containers running the microservices, the virtual switches, routers and gateways enabling the VCN data network, the hypervisors, the Compute Cloud@Customer chassis components, and so on.

Link Local CIDR block

A link-local address belongs to the 169.254.0.0/16 IP range, and is valid only for connectivity within a host's network segment, because the address isn't guaranteed to be unique outside that network segment. Packets with link-local source or destination addresses aren't forwarded by routers.

The link-local CIDR block 169.254.239.0/24, and the IP address 169.254.169.254, are reserved for functions such as DNS requests, compute instance metadata transfer, and cloud service endpoints.