128 bits long (16 bytes). Basic architecture is 64 bits for the network number and 64 bits for the host number. Often, the host portion of an IPv6 address (or part of it) will be derived from a MAC address or other interface identifier.
Depending on the subnet prefix, IPv6 has a more complicated architecture than IPv4.

The number of IPv6 addresses is 1028 (79 228 162 514 264 337 593 543 950 336) times larger than the number of IPv4 addresses. The text form of the IPv6 address is xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx, where each x is a hexadecimal digit, representing 4 bits. Leading zeros can be omitted. The double colon (::) can be used once in the text form of an address to designate any number of 0 bits. For example, ::ffff: is an IPv4-mapped IPv6 address.

Allocation is in the earliest stages. The Internet Engineering Task Force (IETF) and Internet Architecture Board (IAB) have recommended that essentially every organization, home, or entity be allocated a /48 subnet prefix length. This will leave 16 bits for the organization to do subnetting. The address space is large enough to give every person in the world their own /48 subnet prefix length.

IPv6 addresses have two lifetimes: preferred and valid, with the preferred lifetime always <= valid.
After the preferred lifetime expires, the address is not to be used as a source IP address for new connections if an equally good preferred address is available. After the valid lifetime expires, the address is not used (recognized) as a valid destination IP address for incoming packets or used as a source IP address.

Some IPv6 addresses have, by definition, infinite preferred and valid lifetimes; for example link-local (see address scope).

Used to designate the subnet prefix of an address. Written as /nnn (up to 3 decimal digits, 0 <= nnn <= 128) suffix after the print form. An example is fe80::982:2a5c/10, where the first 10 bits comprise the subnet prefix.

IPv6 embeds these functions within IP itself as part of the algorithms for stateless autoconfiguration and neighbor discovery using Internet Control Message Protocol version 6 (ICMPv6). Hence, there is no such thing as ARP6.

In IPv6, address scope is part of the architecture. Unicast addresses have two defined scopes, including link-local and global; and multicast addresses have 14 scopes. Default address selection for both source and destination takes scope into account.

A scope zone is an instance of a scope in a particular network. As a consequence, IPv6 addresses sometimes must be entered or associated with a zone ID. The syntax is %zid where zid is a number (typically small) or a name. The zone ID is written after the address and before the prefix. For example, 2ba::1:2:14e:9a9b:c%3/48.

IPv6 addresses are categorized into three basic types: unicast address, multicast address, and anycast address. See IPv6 address types for descriptions.Configuration is optional, depending on functions required. IPv6 can be used with any Ethernet adapter and can be run over the loopback interface. IPv6 interfaces are self-configuring using IPv6 stateless autoconfiguration. You can also manually configure the IPv6 interface. So, the system will be able to communicate with other IPv6 systems that are local and remote, depending on the type of network and whether an IPv6 router exists.

DNS-Same support for IPv6. Support for IPv6 exists using AAAA (quad A) record type and reverse lookup (IP-to-name). An application may elect to accept IPv6 addresses from DNS (or not) and then use IPv6 to communicate (or not).
The socket API gethostbyname() only supports IPv4. For IPv6, a new getaddrinfo() API is used to obtain (at application choice) IPv6 only, or IPv4 and IPv6 addresses.

For IPv6, fragmentation can only occur at the source node, and reassembly is only done at the destination node. The fragmentation extension header is used.Used similarly by IPv6; however, Internet Control Message Protocol version 6 (ICMPv6) provides some new attributes.
Basic error types remain, such as destination unreachable, echo request and reply. New types and codes are added to support neighbor discovery and related functions.IGMP is replaced by MLD (multicast listener discovery) protocol for IPv6. MLD does essentially what IGMP does for IPv4, but uses ICMPv6 by adding a few MLD-specific ICMPv6 type values.

Fixed length of 40 bytes. There are no IP header options. Generally, the IPv6 header is simpler than the IPv4 header.The IPv6 header has no options. Instead, IPv6 adds additional (optional) extension headers. The extension headers are AH and ESP (unchanged from IPv4), hop-by-hop, routing, fragment, and destination. Currently, IPv6 supports some extension headers.The type of header immediately following the IPv6 header. Uses the same values as the IPv4 protocol field. But the architectural effect is to allow a currently defined range of next headers, and is easily extended. The next header will be a transport header, an extension header, or ICMPv6.Uses different codes to designate an IPv6 traffic class. Currently, IPv6 does not support TOS.IPv6 can be used with any Ethernet adapters and is also supported over virtual Ethernet between logical partitions.

The concept is the same as in IPv4. The single loopback address is 0000:0000:0000:0000:0000:0000:0000:0001 or ::1 (shortened version). The virtual physical interface is named *LOOPBACK.IPv6 has a lower boundary limit on MTU of 1280 bytes. That is, IPv6 does not fragment packets below this limit. To send IPv6 over a link with an MTU of less than 1280 bytes, the link-layer must transparently fragment and defragment the IPv6 packets.Currently, NAT does not support IPv6. More generally, IPv6 does not require NAT. The expanded address space of IPv6 eliminates the address shortage problem and enables easier renumbering.

A simple and convenient network tool that should work like ping, except with content: an IPv6 node may query another IPv6 node for the target's DNS name, IPv6 unicast address, or IPv4 address. Currently, not supported.Packet forwarding has limited support for IPv6. The IBM i TCP/IP stack does not support neighbor discovery as a router.For IPv6, ports work the same as IPv4. Because these are in a new address family, there are now four separate port spaces. For example, there are two TCP port 80 spaces to which an application can bind, one in AF_INET and one in AF_INET6.

IPv6 has an analogous concept, but with important differences.
Addresses are public or temporary, previously termed anonymous. See RFC 3041. Unlike IPv4 private addresses, temporary addresses can be globally routed. The motivation is also different; IPv6 temporary addresses are meant to shield the identity of a client when it initiates communication (a privacy concern). Temporary addresses have a limited lifetime, and do not contain an interface identifier that is a link (MAC) address. They are generally indistinguishable from public addresses.

Conceptually, similar to IPv4. One important difference: IPv6 routes are associated (bound) to a physical interface (a link, such as ETH03) rather than an interface. One reason that a route is associated with a physical interface is because source address selection functions differently for IPv6 than for IPv4. IPv6 enhances sockets so that applications can now use IPv6, using a new address family: AF_INET6.
The enhancements have been designed so that existing IPv4 applications are completely unaffected by IPv6 and API changes. Applications that want to support concurrent IPv4 and IPv6 traffic, or IPv6-only traffic, are easily accommodated using IPv4-mapped IPv6 addresses of the form ::ffff:a.b.c.d, where a.b.c.d is the IPv4 address of the client.

The new APIs also include support for converting IPv6 addresses from text to binary and from binary to text.As with IPv4, an application can designate a source IPv6 address using bind(). Similarly to IPv4, it can let the system choose an IPv6 source address by using in6addr_any. But because IPv6 lines have many IPv6 addresses, the internal method of choosing a source IP is different.

Use the STRIP6 parameter of the STRTCP or ENDTCP command to start or end IPv6. IPv6 might not be started when TCP/IP is started. IPv6 can be started independently at a later time.
Any IPv6 interfaces are automatically started if the AUTOSTART parameter is set to *YES (the default). IPv6 cannot be used or configured without IPv4. The IPv6 loopback interface, ::1, is automatically defined and activated when IPv6 is started.Defined as ::/128 (128 0 bits). It is used as the source IP in some neighbor discovery packets, and various other contexts, like sockets. Socket programming uses ::/128 as in6addr_any.

If you are facing any issues with loading your site, that normal surfing is not loading your site. But loads when you using an VPN, then it must an IPV6 forwarding error. So just remove the IPV6 part and Bind the DNS with IPV4.

Thanks for reading.