What is the difference between IPv4 and IPv6?

Short answer

IPv4 (RFC 791) is the IP version that is 32 bits long and written in dotted decimal form (e.g. 192.0.2.10); IPv6 (RFC 8200), on the other hand, is the version that is 128 bits long, is written in hexadecimal groups separated by colons (e.g. 2001:db8::10) and offers a much larger address space. TR7 supports both versions: when an address is entered in the Add IP form, the version is detected automatically and shown with an IPv4 / IPv6 badge next to the box; addresses of both versions can be added together to the same interface (dual-stack). The version-dependent settings are kept separate: the CIDR range is 0–32 in IPv4 and 0–128 in IPv6; in each route table, Default Gateway(IPv4) and Default Gateway(IPv6) are defined separately; in a cluster, a separate IPv6 Interface IP pair is selected in the VIP Communication (v6) field for the IPv6 VIPs.

Where It Is Used in TR7

Where	Field / label	What for
Network → Interfaces → Add IP	The IPv4 / IPv6 badge next to the address box, CIDR	Showing the version of the address; validating the prefix length according to the version
Network → Route Tables → the pencil icon in the Default Gateway column	Default Gateway(IPv4), Default Gateway(IPv6)	A separate default gateway per route table and per version
Network → Interfaces → Edit Interface (in a cluster)	VIP Communication, VIP Communication (v6)	A separate Interface IP pair for the IPv4 and the IPv6 VIPs
Network → Firewall	Rules (Rule evaluation order)	The IPv4 and IPv6 rule sets are applied separately; a rule with Protocol = ICMP selected is applied as ICMPv6 in the IPv6 set
WEB-CLI	sys-cmd ping (ping), sys-cmd ping6 (ping6)	Testing access to IPv4 and IPv6 destinations

Comparison

	IPv4	IPv6
Address length	32 bits	128 bits
Notation	192.0.2.10	2001:db8::10
CIDR range (TR7)	0–32	0–128
If CIDR is left empty on a VIP (TR7)	/32	/128
Default gateway destination	0.0.0.0/0	::/0
Control messages	ICMP	ICMPv6 (RFC 4443)
Address–MAC resolution	ARP	Neighbor Discovery

Version Rules in TR7

• The two addresses in the Interface IP row (this device and the peer device) must be of the same version; otherwise the record is rejected with the Different Ip versions error (IP).
• In a static route, Destination Network and Gateway must be of the same version. When Default Gateway is selected, whether the destination will be 0.0.0.0/0 or ::/0 is determined from the version of the entered gateway address.
• The IPv4 VIP Communication pair does not enable the IPv6 VIPs; for an IPv6 VIP, an IPv6 pair is selected in the VIP Communication (v6) field.
• Using an IPv6 address on a vService: Can I use an IPv6 address on the frontend?

Common Misconceptions

• "A separate interface is needed for IPv6." IPv4 and IPv6 addresses are added together to the same interface.
• "The default gateway is common to the two versions." In each route table, the IPv4 and the IPv6 Default Gateway are defined separately; an IPv6 Default Gateway is needed to reach IPv6 clients.
• "The IPv4 VIP Communication pair runs the IPv6 VIPs too." The IPv6 VIPs become active only when a VIP Communication (v6) pair is selected.

How it is done in the documentation

• Add IP Address · What Is Add IP Address?
• Add IP Address · IP
• Route Tables · Default Gateway(IPv4)
• Edit Interface · VIP Communication (v6)

Related questions

• Can I use an IPv6 address on the frontend?
• Why can't I type the Frontend IP manually; what should I do to use an IP that is not in the list (e.g. IPv6) on a vService?
• Can I define an IPv6 address for Teacher?
• What is CIDR notation (e.g. 10.0.0.0/24)?