Configure IPv6 on VPS

HolyCloud often assigns an IPv6 block (/64 or delegation) in addition to IPv4 on VPS instances. This guide explains how to enable the address on Linux (Debian/Ubuntu), configure the gateway, and verify connectivity.

Prerequisites

• Linux VPS with IPv6 block visible in the client area (address, gateway, prefix)
• Root access (SSH)
• Services and firewall ready to allow v6 traffic

Values below are examples; replace with those on your VPS sheet.

Retrieve HolyCloud information

1. Client area → VPS → your server.
2. Network / IPv6 section:

- Address: e.g. 2001:db8:1234::2/64

- Gateway: e.g. 2001:db8:1234::1

- Delegated prefix (if routing to VMs): /56 or /64

Note whether the address is bound by NDP (neighbor) or static routing.

Temporary configuration (test)

Public interface often eth0 or ens3:

ip -6 addr add 2001:db8:1234::2/64 dev eth0
ip -6 route add default via 2001:db8:1234::1 dev eth0

Test:

ping -6 -c 3 google.com
curl -6 https://ipv6.google.com

Debian / Ubuntu with netplan

File /etc/netplan/50-cloud-init.yaml (example — backup first):

network:
  version: 2
  ethernets:
    eth0:
      dhcp4: true
      addresses:
        - 2001:db8:1234::2/64
      routes:
        - to: default
          via: 2001:db8:1234::1
      accept-ra: false

Apply:

netplan apply

Debian ifupdown

In /etc/network/interfaces:

iface eth0 inet6 static
    address 2001:db8:1234::2
    netmask 64
    gateway 2001:db8:1234::1

ifdown eth0 && ifup eth0

IPv6 DNS (AAAA)

In your domain DNS zone:

| Type | Name | Value |

|------|-----|--------|

| AAAA | @ | 2001:db8:1234::2 |

| AAAA | www | 2001:db8:1234::2 |

Keep an A IPv4 record for clients without v6.

Verification:

dig AAAA votredomaine.fr +short

Firewall

ufw:

ufw allow OpenSSH
ufw allow 80,443/tcp
ufw enable

nftables — accept ICMPv6 neighbor discovery (essential):

nft add rule inet filter input ip6 nexthdr ipv6-icmp accept

Do not blindly block all ICMPv6.

Web and mail services

• Nginx/Apache: listen on [::]:80 and [::]:443 or dual-stack on all interfaces.
• Postfix: inet_protocols = all if sending mail over v6.

ss -tlnp | grep -E ':80|:443'

Delegated prefix (internal subnets)

If HolyCloud delegates 2001:db8:5678::/56, assign /64 to containers/VMs:

ip -6 addr add 2001:db8:5678:100::1/64 dev docker0

Announce routing policy per support instructions (static route toward VPS).

Troubleshooting

| Symptom | Action |

|----------|--------|

| ping6 gateway OK, no Internet | Default route; datacenter egress filter |

| Address unreachable externally | Firewall; AAAA DNS; service not listening on v6 |

| Gone after reboot | netplan/interfaces persistence |

| « Destination unreachable » | Wrong gateway; incorrect /64 prefix |

Diagnostics:

ip -6 addr show
ip -6 route show
traceroute -6 google.com

Windows Server (overview)

Network settings → Ethernet adapter → IPv6 → manual address and gateway per HolyCloud sheet. Open firewall for relevant services.

Need help?

Ticket with VPS ID, IPv6 block shown in panel, ip -6 route output, and ping -6 result toward gateway.