IPV4 to IPV6: Internet Protocol Version4 and IPv6

IPv6 Introduction

IP version 4 (IPv4) has been a core part of the TCP/IP protocol suite
 and has served well during tremendous growth of the Internet. IPv4, 
mostly called just IP, defines addressing and routing for most corporate
 networks that use TCP/IP as well as the public Internet. Though IPv4 
has been a long-time companion, it has its shortcomings that created the
 need for a protocol that could replace IPv4. That protocol is Internet 
Protocol version 6 or IPv6 for short. IPv6 defines the same general 
functions that are defined by IPv4. However, there are differences in 
detail that we will explore in this chapter.<br />
IP version 6 (IPv6) 
serves as the protocol that will eventually replace IP version 4 (IPv4).
 The most obvious reason for migrating TCP/IP networks from IPv4 to IPv6
 is growth. IPv4 uses a 32-bit address, which allows for a little over 
four billion addresses. It may seem like a pretty large number of 
addresses but the immense growth of networks and the Internet has almost
 exhausted our stock of available IPv4 addresses for new deployments. 
IPv6 uses 128-bit addresses and increases the number of available 
addresses to 2^128, a number so large that we don’t have a word for it.<br />
The
 change from IPv4 to IPv6 is not just about one protocol being replaced 
by another; it impacts many other protocols as well. In this super-sized
 chapter, we start by introducing IPv6 addressing and routing, also 
discussing troubleshooting of the same. We then cover OSPFv3 (Open 
Shortest Path First Version 3) and EIGRPv6 (Enhanced Interior Gateway 
Routing Protocol for IPv6), in detail.<b> </b><br />
<b>The IPv6 Protocols</b><br />
The
 core IPv6 protocol, defined in RFC 2460, describes the concept of a 
packet, addessing for those packets, and the role of hosts and routers. 
The end objective of IPv6 like IPv4 is to enable devices forward packets
 sourced by hosts through multiple routers so that they arrive at the 
correct destination. However, because IPv6 affects several other 
functions in a network as well beyond addressing and packet forwarding, 
many more RFCs must define other details. For example, some RFCs 
describe how to migrate from IPv4 to IPv6, while some other RFCs define 
newer versions of familiar IPv4 protocols for IPv6:<br />
<ul>
<li><b>OSPF Version 3:</b>
 The older version 2 of OSPF works for IPv4 but not for IPv6. So, a 
newer version known as OSPF version 3 (OSPFv3) was created to support 
IPv6.</li>
</ul>
<ul>
<li><b>EIGRP for IPv6:</b> EIGRP for IPv4 runs over 
IPv4 as the transport protocol, communicates only with IPv4 peers, and 
advertises only IPv4 routes. EIGRP for IPv6 follows the same model but 
it can propagate IPv6 prefixes to route IPv6 packets.<b> </b></li>
</ul>
<ul>
<li><b>ICMP Version 6:</b>
 Internet Control Message Protocol (ICMP) worked well with IPv4 to 
provide feedback to senders on packet forwarding especially when packets
 could not be forwarded by a router. ICMP was changed into what is known
 as ICMP version 6 (ICMPv6) to support IPv6.<b> </b></li>
</ul>
<ul>
<li><b>Neighbor Discovery Protocol:</b>
 Address Resolution Protocol (ARP) is used to discover the MAC addresses
 of hosts whose IPv4 addresses are known. IPv6 replaces ARP with the 
more general Neighbor Discovery Protocol (NDP).</li>
</ul>
IPv6 is a 
layer 3 routing protocol and defines a header that holds both the source
 and destination address fields, just like IPv4. The IPv6 header is <i>not</i>
 similar to the IPv4 header and the differences are more than just 
bigger source and destination addresses. The IPv6 header is bigger in 
size compared with the IPv4 header, though it is otherwise simpler for 
the sake of reducing the computational overhead on routers that process 
IPv6 packets. The following diagram displays the IPv6 header:<br />
<div align="center">
<b>Figure 14-1</b> IPv6 Header Format<b> </b></div>
<b><img alt="14-1" class="aligncenter size-large wp-image-1187" height="699" src="http://www.freeccnastudyguide.com/wp-content/uploads/2014/05/14-1-1024x792.png" width="904" /></b><br />
<b>IPv6 Addressing</b><br />
There are three types of IP version 6 (IPv6) addresses:<br />
<ul>
<li><b>Unicast:</b>
 A unicast address identifies a single interface and a packet sent to a 
unicast address is delivered to the one interface identified by that 
address.</li>
</ul>
<ul>
<li><b>Anycast:</b> An anycast address is for a 
set of interfaces typically on different nodes. A packet sent to an 
anycast address is delivered to only one of the interfaces identified by
 that address. The <i>nearest</i> interface, according to the routing protocol metric, gets the packet delivered to it.<b> </b></li>
</ul>
<ul>
<li><b>Multicast:</b>
 A multicast address identifies a set of interfaces typically on 
different nodes just like an anycast address. However, a packet sent to a
 multicast address is delivered to <i>all</i> interfaces identified by that address.</li>
</ul>
If
 you are wondering what happened to broadcast addresses, they don’t 
exist in the IPv6 world. Multicast addresses also function in place of 
broadcast addresses.<br />
<div class="stb-info_box" id="stb-box-618">
<b>Key Concept </b>IPv6 broadcast addresses are a special case of multicast addresses.</div>
Just
 like IPv4, IPv6 addresses of all types are assigned to interfaces, not 
nodes. The IPv6 unicast address of any of a node’s interfaces can be 
used as an identifier for that node.<br />
A single interface may have multiple IPv6 addresses of any type (unicast, anycast, and multicast) and scope.<b> </b><br />
<b>Representation of IPv6 Addresses and Prefixes</b><br />
An IP version 6 address is a 128-bit value written as xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx where each <i>x</i>
 is a hexadecimal digit. There are 8 groups of 4 hexadecimal digits in 
the above representation, with each digit representing four binary 
digits (bits). It is not necessary to write the leading zeros in an 
individual group of four hex digits.<br />
An example of an IPv6 address is:<br />
<div class="stb-grey_box" id="stb-box-1270">
2001:0DB8:0000:0000:0006:0600:300D:527B </div>
The same IPv6 address can also be written as:<br />
<div class="stb-grey_box" id="stb-box-6230">
     2001:DB8:0:0:6:600:300D:527B</div>
There
 must be at least one digit in every group of four digits. That is the 
reason, the groups with all four zeros in the mentioned address are 
replaced with a single zero.<br />
In order to make writing IPv6 
addresses with long strings of zero bits easier, a method is available 
to compress zeros. The special symbol <b>::</b> can be used to represent one or more adjacent groups of 16 bits of zeros. The symbol <b>::</b> can appear only once in an address though. The <b>::</b>
 can also include leading zeros after the last group of 16 zero bits, or
 before the first group of 16 zero bits. For example, the same address 
we mentioned can be squeezed further as:<br />
<div class="stb-grey_box" id="stb-box-1765">
 2001:DB8<b>::</b>6:600:300D:527B</div>
Note that the <b>::</b>
 in above representation replaces two groups of 16 zero bits, as well as
 three leading zeros in the group after those two groups of 16 zero 
bits.<br />
The table below first shows the full representation of a few
 IPv6 addresses, and then shows the short representation making use of 
the <b>::</b> according to rules we described.<br />
<div align="center">
<b>Table 13-1</b> IPv6 Addresses Representation</div>
<div align="center">
<table border="1" cellpadding="0" cellspacing="0" style="width: 504px;"><tbody>
<tr><td width="288"><b>Full Representation</b></td><td width="216"><b>Short Representation</b></td></tr>
<tr><td width="288">2001:0DB8:0000:85A4:0000:08B3:0370:7348</td><td width="216">2001:DB8:0:85A4<b>::</b>8B3:370:7348</td></tr>
<tr><td width="288">FF01:0000:0000:0000:0000:0000:0000:0212</td><td width="216">FF01<b>::</b>212</td></tr>
<tr><td width="288">0000:0000:0000:0000:0000:0000:0000:0001</td><td width="216"><b>::</b>1</td></tr>
<tr><td width="288">0000:0000:0000:0000:0000:0000:0000:0000</td><td width="216"><b>::</b></td></tr>
</tbody></table>
</div>
<br />
 IPv4 divides its address space into three classes: A, B, and C. IPv6 
does not have a concept of classful networks like IPv4. IPv6 subnets or 
prefixes can be of arbitrary length without any classful boundaries. An 
IPv6 address prefix is represented by:<br />
IPv6 address / Length of prefix<br />
For example, the following are four different but valid representations of the 64-bit prefix 20010DB80000ABCD:<br />
<div class="stb-grey_box" id="stb-box-6861">
2001:0DB8:0000:BCD0:0000:0000:0000:0000/64<br />
2001:0DB8::ABCD:0:0:0:0/64<br />
2001:0DB8:0:BCD0::/64</div>
The
 last of the above three formats is most commonly used to represent IPv6
 prefixes. A node can have an address like 
2001:0DB8:0:BCD0:123:4567:89AB:CDEF for the IPv6 prefix 
2001:0DB8:0:BCD0::/64.<br />
IPv6 provides two similar options for unicast addressing:<b> </b><br />
<b>Global Unicast</b><br />
IPv6
 global unicast addresses are similar to public IPv4 addresses. These 
addresses are allocated by the Internet Assigned Numbers Authority 
(IANA) to the Regional Internet Registries (RIRs). RIRs have the task of
 allocation to services providers and other local registries. IANA 
maintains an official list of the current state IPv6 address allocation 
at <a href="http://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml" rel="nofollow">http://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml</a><br />
So, each company is assigned a unique IPv6 address block called a <i>global routing prefix</i>
 – a set of addresses that only one company can use. The company subnets
 its assigned IPv6 address block using addresses only from the block. As
 a result, IPv6 global unicast addresses are unique across the globe.<br />
<div class="stb-info_box" id="stb-box-167">
<b>Key Concept </b>IPv6 global unicast addresses and globally unique, and are analogous to IPv4 public address.</div>
The term <i>global routing prefix</i>
 refers to the idea that routers can have one route that covers all the 
addresses inside an address block, without the need to have individual 
routes for smaller portions of that block. All IPv6 addresses in a 
company should begin with the global routing prefix assigned to it. IPv6
 has plenty of space to allow all companies to have a global routing 
prefix with plenty of addresses, thanks to its 128-bit address size.<br />
Global unicast addresses make up the majority of IPv6 address space. <b> </b><br />
<b>Unique Local</b><br />
IPv6
 unique local addresses are similar to private IPv4 addresses. These 
addresses can be used by companies that do not plan to connect to the 
Internet, and companies that plan to use IPv6 Network Address 
Translation (NAT).<br />
These addresses are readily available, and you 
can simply read documentation and start assigning IPv6 addresses without
 worrying about registration with IANA or another authority. Multiple 
companies can possibly end up using the exact same IPv6 unique local 
addresses, and it works just fine just like private IPv4 addresses.<br />
<div class="stb-info_box" id="stb-box-6434">
<b>Key Concept</b> IPv6
 unique local addresses are only locally significant and don’t have to 
be globally unique, just like IPv4 private addresses.</div>
<b>Address Range of Global Unicast Addresses</b><br />
Global
 unicast addresses make up the majority of the IPv6 address space. 
Originally, Internet Assigned Numbers Authority (IANA) reserved all IPv6
 addresses that begin with hex 2 or 3 as global unicast addresses. This 
address range can be written concisely as 2000<b>::</b>/3. Later, the 
global unicast address range was made wider by a series of RFCs. The 
present state of affairs is that all IPv6 addresses not otherwise 
allocated for other purposes are included in the global unicast address 
space.<br />
Because the number of addresses that sit within the global 
unicast address space is astonishingly large, IANA does not assign 
prefixes from all over the address range.<br />
The type of an IPv6 address can be identified by the initial bits of the address, as explained in below table.<br />
<div align="center">
<b>Table 13-2</b> IPv6 Address Type Identification</div>
<table border="1" cellpadding="0" cellspacing="0" style="width: 573px;"><tbody>
<tr><td width="141"><b>Address Type</b></td><td width="144"><b>Binary Prefix</b></td><td width="288"><b>IPv6 Notation</b></td></tr>
<tr><td width="141">Unspecified</td><td width="144">000…0 (128 bits)</td><td width="288">::/128</td></tr>
<tr><td width="141">Loopback</td><td width="144">000…1 (128 bits)</td><td width="288">::1/128</td></tr>
<tr><td width="141">Multicast</td><td width="144">1111 1111</td><td width="288">FF00::/8</td></tr>
<tr><td width="141">Link-Local Unicast</td><td width="144">1111 1110 10</td><td width="288">FE80::/10</td></tr>
<tr><td width="141">Global Unicast</td><td width="144">(everything else)</td><td width="288">(everything else)</td></tr>
</tbody></table>
<br />
 Anycast addresses are taken from the global unicast address space, and 
are not otherwise distinguishable from unicast addresses.<br />
<b>The Unspecified Address</b><br />
The
 address 0:0:0:0:0:0:0:0 is called the unspecified address and indicates
 the absence of an address. It serves as a place holder and must never 
actually be assigned to a node. As an example of its use, the <i>Source Address</i> field of an IPv6 packet sent by an initializing host before it has learned its own address carries the unspecified address.<b> </b><br />
<b>The Loopback Address</b><br />
The
 unicast address 0:0:0:0:0:0:0:1 is known as the loopback address, and 
can be used by an IPv6 host to send a packet to it. The loopback address
 may be considered the IPv6 equivalent of the IPv4 loopback address 
127.0.0.1. The address is reserved for the special purpose of addressing
 self and must not be actually assigned to an interface. You can think 
of the loopback interface as a virtual interface to an imaginary link 
that goes nowhere. The loopback address is treated as having a 
link-local scope and an IPv6 packet with a destination address of 
loopback must never be sent outside of a single node.<b> </b><br />
<b>Global Unicast Address Format</b><br />
The general format of global unicast address is shown in Figure 13-2.<br />
<div align="center">
<b>Figure 13-2</b> Global Unicast Address Format<b> </b></div>
<b><img alt="Global Unicast Address Format" class="aligncenter size-full wp-image-1188" height="286" src="http://www.freeccnastudyguide.com/wp-content/uploads/2014/05/14-2.jpg" width="872" /></b><br />
<b>Link-Local IPv6 Unicast Address Format</b><br />
The format of link-local addresses that are for use on a single link is given in Figure 13-3.<br />
<div align="center">
<b>Figure 13-3</b> Link-Local Address Format</div>
<img alt="14-3" class="aligncenter size-large wp-image-1190" height="238" src="http://www.freeccnastudyguide.com/wp-content/uploads/2014/05/14-3-1024x270.jpg" width="904" /><br />
<div align="center" style="text-align: left;">
 Link-local
 addresses are supposed to be used for addressing of a single link for 
purposes such as automatic address configuration and neighbor discovery.
 Routers do not forward packets with link-local source or destination 
addresses to other links, thus respecting and enforcing link-local scope
 of these addresses.</div>
Site-local addresses were originally designed
 to be used for addressing inside a site without the need for a global 
routing prefix. They are now deprecated.

IPv6 Introduction

IP version 4 (IPv4) has been a core part of the TCP/IP protocol suite and has served well during tremendous growth of the Internet. IPv4, ...

Subnet masks (IPv4) and prefixes (IPv6) identify

Tukiyooo 0 Internet Protocol Version4 and IPv6 05:56

<div dir="ltr" style="text-align: left;" trbidi="on">A subnet mask separates the IP address into the network and host  addresses (<network><host>). Subnetting further divides the  host part of an IP address into a subnet and host address  (<network><subnet><host>). It is called a subnet mask  because it is used to identify network address of an IP address by  perfoming bitwise AND operation on the netmask.   A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address.<br /><br /><br /> <br /><div class="MsoNormal">subnet can be used to identify all the machines in a building, department, geographic location, or on the same local area network (LAN).</div><div class="MsoNormal"><br /></div><div class="MsoNormal">Dividing an organization's network into subnets allows it to be connected to the Internet with a single shared network address. Subnet masks and prefixes are used when a host is attempting to communicate with another system. If the system is on the same network or subnet, it will attempt to find that address on the local link. If the system is on a different network, the packet is sent to a gateway which will then route the packet to the correct IP address. This is called Classless-InterDomain Routing (CIDR).</div><div class="MsoNormal"><br /></div><div class="MsoNormal">In IPv4, the subnet mask 255.255.255.0 is 24 bits and consists of four 8-bit octets. The address: 10.10.10.0 subnet mask 255.255.255.0 means that the subnet is a range of IP addresses from 10.10.10.0 - 10.10.10.255.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">The prefix-length in IPv6 is the equivalent of the subnet mask in IPv4. However, rather than being expressed in 4 octets like it is in IPv4, it is expressed as an integer between 1-128. For example: 2001:db8:abcd:0012::0/64 specifies a subnet with a range of IP addresses from: 2001:db8:abcd:0012:0000:0000:0000:0000 - 2001:db8:abcd:0012:ffff:ffff:ffff:ffff. The portion in bold is called the network portion of the IP address, or the prefix. The non-bold portion is called the host portion of the IP address, since it identifies an individual host on the network.</div><div class="MsoNormal"><br /></div><div class="MsoNormal"><br /></div><div class="MsoNormal"></div><br /><div class="MsoNormal"> </div><div class="MsoNormal"><span style="color: magenta;"><span style="font-size: large;"><b>IPv4 terms and how they are addressed in IPv6:</b></span></span></div><div class="MsoNormal"><br /></div><div class="MsoNormal"><span style="mso-spacerun: yes;">    </span>IP Address:<span style="mso-spacerun: yes;">  </span>Each device will have an IP address still, but instead of an IPv4 address, it’ll have an IPv6 address.<span style="mso-spacerun: yes;">  </span>Other than the length and slightly different look, this concept is identical</div><div class="MsoNormal"><span style="mso-spacerun: yes;">    </span>Subnet Mask:<span style="mso-spacerun: yes;">  </span>We used to do subnet masks in IPv4 with notation like 255.255.255.0, but in IPv6, while we still do subnetting, the notation is different in two ways.<span style="mso-spacerun: yes;">  </span>We now write subnets using a slash and a number that denotes the masking.<span style="mso-spacerun: yes;">  </span>So it’ll look like IPV6ADDRESS/64 or IPV6ADDRESS/112.<span style="mso-spacerun: yes;">  </span>But when you actually key in the IPv6 address on a system, that /64 or /112 will convert to a hexadecimal number that’ll be in the middle of the IPv6 Address.<span style="mso-spacerun: yes;">  </span>So when you see an IPv6 address, while it is really long, it actually includes the Network Address: Subnet: Device IP Address in that long address string.<span style="mso-spacerun: yes;">  </span>More on this in the “Understand IPv6 Addressing” section below</div><div class="MsoNormal"><span style="mso-spacerun: yes;">    </span>Gateway Address:<span style="mso-spacerun: yes;">  </span>The concept of the network gateway in IPv6 is the same as in IPv4, a gateway address will be designated noting how traffic can be routed out of the current subnet (technically the IPv6 Gateway address is not a formalized standard in IPv6, however Microsoft has included a Gateway setting in their IP Configuration properties page)</div><div class="MsoNormal"><br /></div><div class="MsoNormal">So all of the concepts remain the same, but you’ll see when we get to the IPv6 addressing section that the long IPv6 address includes the Network Address, Subnet, and Unique Device Address all togheter</div><div class="MsoNormal"><br /></div><div class="MsoNormal">How you officially get a block of IPv6 address</div><div class="MsoNormal">So the next question everyone always asks is “How do I get an official IPv6 block of addresses?”<span style="mso-spacerun: yes;">  </span>That’s kind of simple, “How’d you get your official public IPv4 addresses that you have today?”<span style="mso-spacerun: yes;">  </span>Usually the answer is that you got them from your Internet Service Provider (ISP) such as ATT, Sprint, Comcast, or the like when you had your Internet connection line pulled into your building.<span style="mso-spacerun: yes;">  </span>That same concept still applies as the big Internet knows generally where to find you by knowing what region you are in, and what ISP you are connected to by the general range of addressses you are using.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">Of course some of you were the lucky ones that actually got a block of IP Addresses early on when IP addresses were being given away just by writing and asking for a block of addresses.<span style="mso-spacerun: yes;">  </span>For those of you spoiled by owning your own IPv4 block, you're now at the mercy of your ISP to “loan you” a block of their addresses, you no longer own IP addresses (for IPv6) even if you owned IPv4 addresses before.</div>   <br /><br />   <br /><b><span style="font-size: large;"><br /></span></b><br /><b><span style="font-size: large;"> </span></b><br /><div class="MsoNormal"><span style="color: purple;"><b><span style="font-size: large;">What the equivalent of Private network addressing is in IPv6</span></b></span></div><div class="MsoNormal"><br /></div><div class="MsoNormal">So the next question that is asked is “how about Private (internal) network addresses, do they exist in IPv6?”, and the answer is Yes.<span style="mso-spacerun: yes;">  </span>So if you are just fiddling around with IPv6 in your lab, or you want to do the equivalent of network address translation where you have private addresses for your internal servers and systems, then you can use IPv6 private addressing, or what is called Unique Local Addresses (ULA). In the IPv4 world, private addresses include 10.0.0.0-10.255.255.255, and 172.16.0.0-172.31.255.255, and 192.168.0.0-192.168.255.255.<span style="mso-spacerun: yes;">  </span>In the Ipv6 world, the ULA space is fc00::/7, or basically anything that starts with FD in the IPv6 address, so fdxx:xxxx:xxxx…</div><div class="MsoNormal"><br /></div><div class="MsoNormal">Do note though, if you use Unique Local Addressing in IPv6, these addresses cannot be routed on the Internet.<span style="mso-spacerun: yes;">  </span>These devices will always have to remain behind a router (good and bad). Good is that you control these devices like you do IPv4 devices on the “inside” of your network.<span style="mso-spacerun: yes;">  </span>So some may say using a ULA is more secure because the device cannot be accessed externally.<span style="mso-spacerun: yes;">  </span>However, if everything is on the inside of a firewall, no one can access the device anyway. And because there are so many IPv6 addresses, it’s not like someone will “guess” the address of the destination devices either.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">Another argument against Unique Local Addressing is the whole concept of IPv6 is to be able to have IPv6 devices globally routable so that in the future, you want to have your IPv6 systems talk to other IPv6 systems directly without having to translate addresses through a router (from private to public addressing), having publicly accessible IPv6 addresses on internal devices is planning for the future of what will come in IPv6 communications.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">This is a tough one.<span style="mso-spacerun: yes;">  </span>We got convinced by ISPs to setup Network Address Translation (NAT) and hide everything behind a firewall with non-routable private addresses and we think we have security.<span style="mso-spacerun: yes;">  </span>But if we simply use routable IPv6 addresses and create secured subnets protected by routers and firewalls, we’re effectively getting the same security without having to have the overhead of address translation.<span style="mso-spacerun: yes;">  </span>I highly encourage organizations to consider implementing publicly addressable IPv6 addresses for all devices.</div><div class="MsoNormal"><br /></div><div class="MsoNormal"></div><br /><div class="MsoNormal"> </div><div class="MsoNormal">In IPv4, as a 32-bit address, we separated the 32-bits into 4 octets separated by periods (or dots), so it looks like 10.12.2.200.<span style="mso-spacerun: yes;">  </span>We’d give the address a Subnet mask like 255.255.0.0 which means the network is 10.12 and the device address is 2.200. </div><div class="MsoNormal"><br /></div><div class="MsoNormal">In IPv6, as a 128-bit address, rather than breaking into dot separated octets that would end up being 16 numbers (separated by periods) long, IPv6 uses hexadecimals in a double-octet format separated by a colon, so effectly written out as 8 sets of “numbers” (since this is hexadecimal, it is 0 thru 9, and a thru f) so something like<span style="mso-spacerun: yes;">   </span>fd30:0000:0000:0001:ff4e:003e:0009:000e</div><div class="MsoNormal"><br /></div><div class="MsoNormal">IPv6 addressing allows you to drop preceding zeros in the format, so the above could be simplied as:<span style="mso-spacerun: yes;">  </span>fd30:0000:0000:1:ff4e:3e:9:e</div><div class="MsoNormal"><br /></div><div class="MsoNormal">And when you have a double-octet group that is nothing but zeros (0000) you can replace the entire grouping with a ::, so this further simplies the above to look like fd30::1:ff4e:3e:9:e<span style="mso-spacerun: yes;">  </span>(note:<span style="mso-spacerun: yes;">  </span>You can only have 1 set of :: in an IPv6 address, so if you have 2 groupings of zeros, you would put the :: on one set but not on the second set to truncate.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">How to subnet IPv6</div><div class="MsoNormal">So I told you I’d explain how subnetting works in IPv6.<span style="mso-spacerun: yes;">  </span>For the above address, it’s not just one massively long IP address.<span style="mso-spacerun: yes;">  </span>It’s actually broken down into 3 parts, the Network Address, the Subnet Address, and the Device Address.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">The Network Address is the first 48-bits of the address, or since they are grouped in 16-bit groupings, effectively the first 3 groups of numbers designate the network.<span style="mso-spacerun: yes;">  </span>For the above example, the Network Address is fd30:0000:0000.<span style="mso-spacerun: yes;">  </span>For those getting their IPv6 addresses from an ISP, the first part of this Network Address will be the same for all of the customer’s of the ISP, which will designate the region and ISP. <span style="mso-spacerun: yes;"> </span>If you are doing Unique Local Addressing (ie: IPv6 private addressing), you could effectively just address it as fd00:0000:0000 where fd designates this as a ULA, and that you are working with a single common network.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">The Subnet Address is the next 16-bits of the address, or as addresses are grouped in 16-bit groupings, the next group in the IPv6 string.<span style="mso-spacerun: yes;">  </span>For the above example, that would be 0001.<span style="mso-spacerun: yes;">  </span>Instead of a Subnet Mask, in IPv6, you just note the Network Address and the Subnet Address, and that’ll give this address a specific designation of the Network that this device is on, and the Subnet that this device is one.<span style="mso-spacerun: yes;">  </span>This is where I noted IPv6 is more efficient than IPv4 as each packet has everything a router needs to route the information along, instead of having to add or append routing information, or look to a completely separate subnet mask parameter to work backwards into the address.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">The last 64-bits (or 4 groupings) is the unique device address, in this case, the device is specifically ff4e:003e:0009:000e.</div><div class="MsoNormal"><br /></div><div class="MsoNormal">With 16-bit allocated to subnets, and 64-bits allocated to devices on a subnet, that means a single Network Address can have 65,535 subnets each with over 18-quintillion (18 with 18 zeros after it) devices.<span style="mso-spacerun: yes;">  </span>And with 48-bits allocated to the Network Address header of the IPv6 address, that’s 281-trillion networks (with 65,535 subnets, with 18-quintillion devices).</div>   <br /><br />  </div>

Subnet masks (IPv4) and prefixes (IPv6) identify

A subnet mask separates the IP address into the network and host addresses (<network><host>). Subnetting further divides the h...

IPv6 Introduction

Subnet masks (IPv4) and prefixes (IPv6) identify

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