Frequently Asked Questions

What is the main driving force behind IPv6?

IPv4 address depletion is the major concern that drives the need for a

new address space for Internet.

Why are so many IP addresses ever needed?

Even at this moment IPv4 is unable to provide globally unique addresses to all internet users.

NAT, DHCP, CIDR and other mechanisms have come into play in order to save the existing IPv4

addresses from complete exhaustion.

IPv4 was never thought to be so widely used when it was invented,

and with the Asian and other new economies booming, IP requirements have increased as

never before.

Also, with all devices, including mobile phones, home appliances & virtually all devices

becoming "IP Aware", a new, much larger address space has become essential.

IPv6 with 128 bits is designed to meet this new paradigm in mind, where each individual or

facility will use so many unique IPs for his/her/its requirements.

Is IPv6 really going to replace IPv4?

Not in the short term but eventually, YES.

IPv6 was never meant to replace IPv4 from one day to the next. IPv6 is simply another layer 3

protocol that can independently exist in parallel to IPv4 (like IPX). To facilitate the migration to

IPv6 quite a few mechanisms were developed along with IPv6. These mechanisms for example

bridge non IPv6 capable network devices or provide a way of communication between IPv4 and

IPv6 devices, so IPv6 can be introduced to the Internet on a step-by-step basis without a flag-day.

For the moment and most likely for some time to come the ideal state for any network is a

dual-stack IPv4/IPv6 infrastructure. Only after that is in place does it make sense to move more

and more parts of the network to IPv6-only operating mode.

Can IPv4 communicate with IPv6?

No not really. It can get translated though.

IPv4 and IPv6 are independent layer 3 protocols. They have no way of communicating with one another by themselves. Quite a few socalled "transition mechanisms" to facilitate the migration are available. These mechanisms put the question into another perspective, so it can be answered with a Yes after all.

One has to differentiate between two types of transition mechanisms; one, where it is simply a requirement that IPv6 traffic may be able to cross parts of the Internet, which are IPv4-only (also called "tunnelling techniques), the other where IPv6-only hosts actually need to talk to IPv4-only hosts and "translation" of IPv4-traffic into IPv6-traffic of some kind comes into play.

Is IPv6 "better" than IPv4?

IPv6 is a further development of IPv4. Aside from the much bigger address space it also comes with quite a few other improvements and enhancements. Several mistakes that were made with IPv4 are rectified and the header and protocol itself was stripped from redundant information. It includes IPSec and QoS functionality which had to be painstakingly added to IPv4 as a not quite satisfying optional feature. Based on this experience with IPv4 the new version of the Internet protocol is now also much easier extendible with as yet unknown new features and options with extended headers.

How long is an IPv6 address?

IPv6 Address space is 128 bits wide

How do I get IP addresses for my network?

You can get IP addresses from your ISP (if the ISP has IPv6). If you need provider independant addresses, you need to submit an application to the RIR (APNIC) at www.apnic.org

What does an IPv6 packet look like?

IPv6 packet header has the above format. Multiple headers may exist as indicated by the "next-header" option.

The payload can have a size of up to 64KiB in standard mode, or larger with a "jumbo payload" option.

What is a 'Jumbogram'?

IPv4 limits packets to 64 KiB of payload. IPv6 has optional support for packets over this limit, referred to as jumbograms, which can be as large as 4 GiB. The use of jumbograms may improve performance over high-MTU networks. The presence of jumbograms is indicated by the Jumbo Payload Option header.

Why is there 64 bits for a host address?

There are two main reasons for having 64 bits for a Host Address;

(a) It was proposed at IETF to use Layer Two (MAC) address for Host Address creation,

which is used for EUI-64 stateless autoconfiguration.

But not all MAC formats are 48 bits long (Ex: Some 802 series MACs are 64 bits,

E.164 Teleph. No. s in BCD format is 16 bits etc). Therefore, 64 bits was proposed.

(b) Although MAC-48 format is quite sufficient for current usage,

64 bit MAC space will provide space for future possible expansion.

What if my network does not implement IPv6 now?

If not implemented, your network will work fine with IPv4 only. It is expected that IPv4 will

exist for a long time to come. But, you will not have any IPv6 accessabilty,

unless somekind of translation mechanism is provided.

Please note that IPv6 is not backward compatible. In the long term,

all networks will need IPv6, since majority of new networks will be in IPv6, and even IPv6 only.

If my ISP is NOT suporting IPv6, how can I connect to IPv6?

You can use multiple methods to connect to IPv6, while being connected to IPv4 only ISP. Some available methods are as follows.

(a) Connect to a Tunnel Broker (Ex: Hurricane Electric)

(b) Use automatic 6-to4 tunneling

Does Microsoft Windows support IPv6?

Windows Vista and Windows Server 2008 support an integrated IPv4 and IPv6 implementation known as the Next Generation TCP/IP stack. For more information, see Next Generation TCP/IP Stack in Windows Vista and Windows Server 2008.

Microsoft provides supported IPv6 implementations for Windows Server 2003, Windows XP with Service Pack 1 (SP1) or later, and Windows CE .NET 4.1 or later.

What other OSs support IPv6?

Linux, Solaris, BSD, HP-UX, MacOS, AIX and many other OSs provides IPv6 support.

(Ref: http://www.join.uni-muenster.de/Implementationen/Betriebsysteme.php?lang=en)

Why V6 after V4? Where is V5?

A protocol named Streaming Protocol (ST) was create during 1970s for experimental transmission of voice, video & distributed simulation, which was called 'IP version5', aka 'Magical-5'. This protocol dies without much use.

How is DNS implemented for IPv6?

IPv6 addresses are represented in the Domain Name System by AAAA resource records (so-called quad-A records) for forward lookups.

Reverse lookup takes place under ip6.arpa (previously ip6.int), where name space is allocated by the ascii representation of nibble units (digits) of the hexadecimal IP address. This scheme, which is an adaptation of the IPv4 method under in-addr.arpa, is defined in RFC 3596.

Will IPv4 DNS server resolve IPv6 Quad-A requests?

Yes, your DNS query will be via IPv4 and the server will respond with a AAAA (IPv6) response, along with IPv4 responses.

Your host will give priority for AAAA response, if both IPv4 & IPv6 responses are given.

Try this out on a Windows host commnad prompt:

>nslookup

> set type=aaaa

> www.ipv6.sltnet.lk or

> www.apnic.org

Are there IPv6 DNS servers?

Yes. There are a lot of open and commercial DNS servers with IPv6 IPs.

(list of open servers http://bgp.he.net/ipv6-progress-report.cgi?section=ipv6_rdns_with_v6)

But, if you have dual-stack(both v4 & v6), you do not need a separate IPv6 DNS server.

How do I host my sub domain with a IPv6 IP in the DNS server?

If you want to place IPv6 entries in your subdomain ipv6.example.com you can simply add them to your main zonefile as follows;

;$ORIGIN example.com.

www IN A 10.10.10.1

www.ipv6 IN AAAA 2001:400:10:100:201::1

What is a "Tunnel Broker"?

A tunnel broker provides access to IPv6 networks for a network or a host who does not have direct access to IPv6 via tunnels. There are commercial and free tunnel brokers. Once you register with the broker, they will provide you with a global IPv6 block to be used in the network. Only problem is that all v6 traffic needs to go through the tunnel, which impacts pereformance.

What is the best way to connect to IPv6?

The best way to connect is to connect to a local ISP who provides IPv6 connectivity via Dual-stack. This will provide best performance and reduce stress on the network. It is also easier to manage than tunneling.

What tunneling protocols shall I use for Internal tunnels?

(a) ISATAP (Intra-Site Automatic Tunnel Addressing Protocol); it is used for automatic deployment of IPv6 in IPv4 sites. ISATAP specifies an IPv6-IPv4 compatibility address format as well as a means for site border router discovery. ISATAP also specifies the operation of IPv6 over a specific link layer - that being IPv4 used as a link layer for IPv6.

(b) v6-in-v4 tunneling; manually created tunnels over v4 network

(d)

What prefix lengths will be visible in the global Internet routing table?

Right now, prefixes upto /48 or less lengths are visible in the routing tables.

How is Multi-homing arranged in IPv6?

What is EUI-64?

The IEEE EUI-64 address represents a new standard for network interface addressing. The company ID is still 24-bits in length, but the extension ID is 40 bits, creating a much larger address space for a network adapter manufacturer. The EUI-64 address uses the U/L and I/G bits in the same way as the IEEE 802 address.

Mapping IEEE 802 addresses to EUI-64 addresses:

To create an EUI-64 address from an IEEE 802 address, the 16 bits of 11111111 11111110 (0xFFFE) are inserted into the IEEE 802 address between the company ID and the extension ID. The following illustration shows the conversion of an IEEE 802 address to an EUI-64 address.

Mapping EUI-64 addresses to IPv6 interface identifiers:

To obtain the 64-bit interface identifier for IPv6 unicast addresses, the U/L bit in the EUI-64 address is complemented (if it is a 1, it is set to 0; and if it is a 0, it is set to 1).

Why is U/L bit inverted in Modified EUI-64 IPv6 Addresses?

(a) To make it easier for administrators to hand configure non-global id's, when hardware tokens are not available (Ex: for serial links, tunnel ends etc.) Alternative would have been of the form 0200:0:0:1, 0200:0:0:2 etc instead of simpler ::1, ::2 etc.

(b) To allow developement of future technology that can take advantage of interface IDs of global scope.