IPv4 and IPv6 overview

Quick answer: IPv4 (e.g. 203.0.113.10) is the classic address format — scarce and therefore paid per address. IPv6 (e.g. 2001:db8::1) is the modern format with a practically unlimited supply, usually provided as a whole subnet. Run dual stack (both at once) where possible: IPv4 for universal reach, IPv6 for the growing share of v6-only clients.

Overview

IPv4's 4.3 billion addresses ran out years ago, which is why every extra IPv4 costs money and needs justification. IPv6's 128-bit space fixes scarcity — a server typically receives a /64 subnet with more addresses than the whole IPv4 Internet. Adoption keeps growing, but plenty of networks are still v4-only, so servers serve both.

Before you start

• Your server's assigned addresses are listed on the service page in the Client Area.
• IPv6 availability can depend on location — ask support what your service includes.

Key differences at a glance

1. Format: IPv4 — four numbers 0-255 (93.184.216.34); IPv6 — eight hex groups, zeros compressible (2001:db8:0:0:0:0:0:1 → 2001:db8::1).
2. Allocation: IPv4 — individual addresses, justified and paid; IPv6 — whole subnets, effectively free.
3. NAT: common in IPv4, unnecessary in IPv6 — every device can have a public address (firewall still mandatory!).
4. DNS records: IPv4 uses A, IPv6 uses AAAA — publish both for dual-stack sites.
5. Tooling: ping/ping -6, ip -4 addr/ip -6 addr, mtr -4/mtr -6.

Common issues

• Publishing AAAA before configuring v6: v6-capable visitors then hit a dead address — configure and test first (see IPv6 setup).
• Forgetting the v6 firewall: your iptables/ufw IPv4 rules do NOT protect the v6 stack — mirror them (ip6tables / ufw handles both).
• Assuming everyone has v6: keep IPv4 for reach; v6-only hosting cuts off a large share of the Internet.

When to contact support

To confirm your IPv6 allocation, get the gateway details, or request IPv6 where it isn't pre-assigned, open a ticket with your service ID.

Frequently asked questions

Do I need both IPv4 and IPv6?

Ideally yes (dual stack): IPv4 for universal reach, IPv6 for modern networks. IPv6-only would cut off a large share of visitors.

Why is IPv4 paid and IPv6 practically free?

IPv4 address space is exhausted, so each address is a scarce resource. IPv6 space is vast — servers typically get a whole /64 subnet.

Does my firewall protect IPv6 automatically?

Not necessarily — raw iptables rules do not apply to IPv6. Mirror rules with ip6tables, or use ufw/firewalld which handle both.

Related articles

• How to configure IPv6 on VPS
• How to request additional IPv4 for VPS
• Basic terminology: VPS, VDS, bandwidth, IP, traffic
• Cloud2Y network overview

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