Implement and manage Virtual Cloud Networks

Summary

A VCN is the basic building block for Oracle Cloud Infrastructure.

Reference

• Infrastructure Services
• Networking
• VCNs and Subnets
• Overview of VCNs and Subnets

CIDR Blocks

Minimum IPv4 CIDR prefix length is 16 which gives 65,533 host addresses. Maximum is 30 which gives one (1) host address. One (1) IP address each, in each subnet, is reserved for:

1. Subnetwork address
2. Subnet router
3. Broadcast address

IPv6 address provided by OCI has a /56 prefix

VCN

Resides in a single region but can span multiple Availability Domians. Can have multiple CIDR blocks.

Components of a VCN are:

• Subnet (has a single CIDR block)
• Route Table
• DHCP Options (needed for DNS)
• Gateways: Internet, NAT, Service, Local Peering, Dynamic Routing.
• Network Security Group
• Security List

Run the following commands to list all VCNs in the Sandbox compartment:

sandbox_comp_ocid=$(       \
  oci iam compartment list \
  --name 'Sandbox'         \
  --query 'data[0].id'     \
  --raw-output             \
)
oci network vcn list                                                            \
  --compartment-id ${sandbox_comp_ocid}                                         \
  --query 'data[*].{"Display Name":"display-name","CIDR Blocks":"cidr-blocks"}' \
  --output table   

The sample output is:

+-----------------+--------------+
| CIDR Blocks     | Display Name |
+-----------------+--------------+
| ['10.0.0.0/16'] | sandbox-vcn  |
| ['10.0.0.0/16'] | sandbox-vcn  |
+-----------------+--------------+

Note: The display name and CIDR Blocks are duplicates.

Create VCN

The easiest way to create a VCN is to the wizard under the Networking menu.

The Terraform code to create a VCN is:

resource "oci_core_vcn" "sandbox_vcn" {
  compartment_id                = local.sandbox_comp_ocid
  cidr_blocks                   = ["10.0.0.0/16"]
  display_name                  = "sandbox-vcn"
  dns_label                     = "sandbox"
}

The equivalent OCI CLI command is:

oci network vcn create                        \
  --compartment-id      ${sandbox_comp_ocid}  \
  --cidr-blocks         '["10.0.0.0/16"]'     \
  --display-name        "sandbox-vcn"         \
  --dns-label           "sandbox"'

Sample output is:

{
  "data": {
    "byoipv6-cidr-blocks": null,
    "cidr-block": "10.0.0.0/16",
    "cidr-blocks": [
      "10.0.0.0/16"
    ],
    "compartment-id": "ocid1.compartment.oc1..aaaaaaaamoo6uz2qmix2adls2cgoqxxhdt4wuam3wbcrw6co6z4osweos6da",
    "default-dhcp-options-id": "ocid1.dhcpoptions.oc1.ap-sydney-1.aaaaaaaajs3e534mob23c33ccdbwerpj6bia2ue2tnrtb3xv7xgloc5dm7sa",
    "default-route-table-id": "ocid1.routetable.oc1.ap-sydney-1.aaaaaaaaw2dcufmlxjnqsg6n6avg3ofgbjvhn7rq2h7o5d2kxtxraozw3yia",
    "default-security-list-id": "ocid1.securitylist.oc1.ap-sydney-1.aaaaaaaaav2gpqwu22jggxg7is7oqpk3mv23ib3weefq6kzjh5n3dz63ukna",
    "defined-tags": {
      "Oracle-Tags": {
        "CreatedBy": "default/tenancy_admin",
        "CreatedOn": "2024-07-15T18:02:30.948Z"
      }
    },
    "display-name": "sandbox-vcn",
    "dns-label": "sandbox",
    "freeform-tags": {},
    "id": "ocid1.vcn.oc1.ap-sydney-1.amaaaaaa63mv4jyaj5mtika6dmntjldwgucszjglov34ko43itr6uusiw65q",
    "ipv6-cidr-blocks": null,
    "ipv6-private-cidr-blocks": null,
    "lifecycle-state": "AVAILABLE",
    "time-created": "2024-07-15T18:02:31.059000+00:00",
    "vcn-domain-name": "sandbox.oraclevcn.com"
  },
  "etag": "9b6e3874"
}

Manage VCN

According to the help text for the oci network vcn command, the following verbs are available to manage VCNs:

• add-ipv6-vcn-cidr
• add-vcn-cidr
• change-compartment
• create
• delete
• modify-vcn-cidr
• remove-ipv6-vcn-cidr
• remove-vcn-cidr
• update

Lab

This topic is covered by Lab 3-1: Networking - Virtual Cloud Network: Create and Configure a Virtual Cloud Network.

A VCN is a software-defined network specific to OCI tenancy or a compartment in a specified region.

Upon creation, a VCN automatically includes route tables, security lists (with default security rules), and a set of DHCP options. The VCN also has access to a DNS resolver.

A VCN that is launched with the OCI VCN Wizard tool automatically creates the following:

• Public and Private subnets
• Internet Gateway (IG)
• NAT Gateway (NAT)
• service Gateway (SG)
• Two Route Tables (RT)
• Two Security Lists (SL)