Create a Dual-Stack Subnet

This guide helps you create a subnet that supports both IPv4 and IPv6. After it's created, Instances in this subnet automatically receive an IPv6 address via DHCPv6.

What is a dual-stack Subnet

A dual-stack Subnet supports both IPv4 and IPv6 at the same time. Each private IP allocation receives both an IPv4 and an IPv6 address together.

Before you start

• Logged in to the Console Portal with the subnet:Create permission
• The VPC in use has stackMode = dual (configured by FPT Cloud) — see Request a Dual-Stack VPC from FPT Cloud if you don't have one
• The VPC has at least one /64 prefix not yet allocated to another subnet

Steps

Make sure the dual-stack VPC is selected in the VPC switcher at the top of the Console Portal, then:

1. Go to Network → Subnets.
2. Click Create subnet.
3. Fill in the IPv4 fields:
   • IPv4 CIDR (for example, 10.42.10.0/24)
   • IPv4 gateway (for example, 10.42.10.1)
4. Expand the Advanced section and tick Enable IPv6 (dual-stack).
   • The hint reads: "Allocate a /64 prefix from this VPC's IPv6 parent pool. Addresses are assigned via DHCPv6 Stateful."
5. Click Create subnet.

Result

• The Subnet is created with IPv6 enabled.
• The system automatically allocates a /64 prefix from the VPC's IPv6 Parent Pool, assigned via DHCPv6 Stateful.
• The Subnet appears in the list with its IPv6 CIDR and IPv6 gateway filled in.

Open the subnet to see its detail, where a Dual-stack badge appears next to the name along with the IPv6 CIDR and IPv6 gateway.

When IPv6 can't be enabled

Cause	Solution
The selected VPC is not dual-stack (stackMode = ipv4)	Switch to a VPC with stackMode = dual (configured by FPT Cloud)
The VPC is dual-stack but out of /64	Contact FPT Cloud to create a new VPC, or delete a dual-stack subnet no longer in use

note

After a subnet is created, IPv6 cannot be added or removed — create a new subnet if you want to change it.

Next steps

• Create an Instance in a Dual-Stack Subnet