VPC - Concepts

CIDR block

An IPv4 CIDR block and an IPv6 CIDR block are defined for each Scaleway Private Network at the time of creation. When you attach a resource (e.g. an Instance) to the network, DHCP will assign one IPv4 and (if the resource is IPv6-compatible) one IPv6 address from the designated blocks to that resource.

Classless Inter-Domain Routing (CIDR) blocks represent a range of IP addresses sharing the same network prefix. An example of an IPv4 CIDR block is 172.16.16.0/22, while an IPv6 CIDR block looks like fd12:3456:789a:1::/64.

• The prefix of the CIDR block (e.g. 172.16.16.0) represents the network address, and the starting point of the IP address range.
• The suffix of the CIDR block (e.g. /22) represents the network size. This is also known as the prefix length or subnet mask bit size. It states how many bits of the prefix are used to designate the network itself, with the remaining bits therefore being available to designate specific hosts on the network.

Default VPC

Scaleway currently has three regions: Paris, Amsterdam and Warsaw. One default VPC is automatically created for each region, in each Scaleway Project. Any new Private Networks that you create will be added to the default VPC for their region, unless you override this by specifying a different VPC.

DHCP

Dynamic Host Configuration Protocol (DHCP) is a network management protocol for dynamically assigning IP addresses and other configuration parameters to devices in a Private Network.

Managed DHCP was previously a feature of Scaleway’s Public Gateway, but is now built into Private Networks. A CIDR block representing a range of available IP addresses is defined when creating the Private Network, and when you attach a resource to the network it is assigned a static, private IP address from this subnet. These IP addresses are managed by our internal IPAM, which acts a single source of truth and ensures full consistency. There is no need for users to manually assign private IP addresses to their resources as they join or leave the network. However, you can choose to assign particular reserved IP addresses if you wish.

Even with automatic IP address assignment, thanks to managed DHCP, a resource’s IP address will never change as long as that resource is not detached from the Private Network. It remains stable across reboots and long poweroffs. The IP is allocated when the resource is attached, and released only when the resource is detached or deleted.

The IPv4 address of Private Networks’ DHCP server is 169.254.169.254. The IPv6 address is fe80:200:22ff:fe05:ca1e.

DNS

The Domain Name System (DNS) is a naming system for devices connected to the internet or Private Networks. Most prominently, DNS servers translate text-based domain names (e.g. www.scaleway.com) to numerical IP addresses (e.g. 51.158.66.220).

Private Networks benefit from managed DNS, which resolves the hostnames of attached resources into their IP addresses. The hostname for a given device is generally the name defined when creating the resource (and which in the case of an Instance, for example, displays in the shell when connected to that resource by SSH). See full information on reaching a resource via its hostname.

When a Private Network is attached to a legacy Public Gateway however, the gateway’s DNS takes priority over that of the Private Network, to allow hostname resolution across the different Private Networks it may be attached to.

IPAM

IP Address Manager (IPAM) is Scaleway’s tool for planning, tracking and managing the IP address space of Scaleway products. It acts as a single source of truth for the IP addresses of Scaleway resources. See our dedicated IPAM documentation for full information.

IPv4

Internet Protocol Version 4 is the standard protocol used for IP addresses. Composed of 32 bits, when written in human-readable form an IPv4 address is generally shown as four octets separated by periods, e.g. 151.115.59.87.

When a resource is attached to a Private Network, it has a private IPv4 address on that network. Scaleway Private Networks’ DHCP functionality assigns this private IPv4 address (as well as an IPv6 address, if the resource is IPv6-compatible) when the resource joins the network. Alternatively you can reserve and attach an IP address of your choice with IPAM.

IPv6

Internet Protocol Version 6 is the most recent version of the IP protocol used for IP addresses. Composed of 128 bits, written in human-readable form, an IPv6 address can be shown as eight groups of four hexadecimal digits separated by a colon, e.g. 2001:0DB8:0000:0003:0000:01FF:0000:002E. This can also be notated as 2001:DB8::3:0:1FF:0:2E.

When an IPv6-compatible resource is attached to a Private Network, it has a private IPv6 address on that network. Scaleway Private Networks’ DHCP functionality assigns this private IPv6 address when the resource joins the network. Alternatively you can reserve and attach an IP address of your choice with IPAM.

Private IP address

A private IP address identifies a resource on a Private Network. When you attach a resource (e.g. an Instance) to the network, you can either use a reserved IP address, or let DHCP assign one IPv4 and (if the resource is IPv6-compatible) one IPv6 address from the designated CIDR blocks to that resource.

For example, a private IPv4 address may resemble 172.16.16.2/22. This format encapsulates information both about the resource’s IP address, and also the subnet (Private Network) itself. If you configure an Instance manually with this address, it sets both the correct IP and a route to the correct subnet.

Private Networks

Private Networks let you connect Scaleway resources across multiple AZs within the same region. Attached resources can then communicate between themselves in an isolated and secure layer 2 network, away from the public internet.

Dynamic Host Configuration Protocol (DHCP) is built into each Private Network, making it easy to manage the private IP addresses of your resources on the network.

Read our dedicated documentation on creating a Private Network.

Region and Availability Zone

A region is a geographical area, such as France (Paris: fr-par) or the Netherlands (Amsterdam: nl-ams), in which Scaleway products and resources are located. It can contain multiple Availability Zones.

An Availability Zone refers to the geographical location within a region, such as waw-1 (Warsaw, Poland), in which your Scaleway resource will be created. The latency between multiple AZs of the same region is low, as they have a common network layer.

For an extensive list of which regions and AZ a resource is available in, refer to our Product availability guide.

Route table

A route table is used to manage and control the routing of traffic within a VPC. The routes within a route table tell the VPC where to send traffic trying to get to a specific destination IP address. One line in the route table corresponds to one route.

Routes can be of the following types:

• Auto-generated, fully managed Local subnet routes for routes to Private Networks.
• Auto-generated, fully managed Default route to internet for routes to Public Gateways.
• Custom routes created by the user.

When deciding which route to apply, the route table reads the routes from most specific to least specific, in terms of destination IP range. The first matching route encountered is the one that determines the path for the traffic. Therefore, a route to destination 172.16.8.0/22 is applied before a default route to 0.0.0.0/0.

Routing

Routing allows Private Networks in the same VPC to communicate with each other, via managed and custom routes. Routing is activated by default whenever you create a new VPC, and can be activated on pre-existing VPCs by following these steps.

Each routed VPC has a route table which is automatically populated with routes to each Private Network in the VPC, as well as to any attached Public Gateways. These routes allow the VPC to automatically route packets between its Private Networks, or from a given Private Network to its attached Public Gateway when the destination is outside the VPC. You can also create your own custom routes.

Read more about how routing works in our detailed guide.

vRouter

A vRouter is a virtualized router that sits inside a VPC and manages layer 3 routing between its resources. It holds the route table for the VPC. A VPC’s vRouter is entirely managed by Scaleway, and not directly configurable by the user.

VPC

VPC allows you to build your own Virtual Private Cloud on top of Scaleway’s shared public cloud. Within each VPC, you can create Private Networks and attach Scaleway resources to them, as long as the resources are in an AZ within the network’s region.

One default VPC for every available region is automatically created in each Scaleway Project.

VPC currently comprises the Private Networks product. Layer 2 Private Networks sit inside the layer 3 VPC.

More features and resources will be coming to VPC in the future.