An Ipv6 address uses
128 bits
as opposed to
32 bits
in IPv4.
IPv6 addresses are written using hexadecimal, as opposed to dotted decimal in IPv4. See
Binary numbers explained
Because an hexadecimal number uses 4 bits this means that an IPv6 address consists of
32 hexadecimal numbers.
These numbers are grouped in 4’s giving
8 groups or blocks
. The groups are written with a : (colon) as a separator.
group1:group2: ……etc…. :group8
Here is an
IPv6 address example:
Note:
Because of the length of IPv6 addresses various
shortening techniques
are employed.
The main technique being to omit
repetitive 0’s
as shown in the example above.
Network And Node Addresses
In IPv4 an address is split into two components a
network component
and a
node component.
This was done initially using
Address classes
and later using
subnet masking
.
In IPv6 we do the same. The first step is to split the address into two parts.
The address is split into 2
64 bit
segments the top 64 bits is the
network part
and the lower 64 bits the node part:
The upper 64 bits are used for
routing.
The lower 64 bits identify the address of the interface or node, and is derived from the actual physical or
MAC address
using IEEE’s
Extended Unique Identifier
(EUI-64) format. See this
Wiki
description for exact details.
If we look at the upper 64 bits in more detail we can see that it is split into 2 blocks of
48
and
16 bits
respectively the lower 16 bits are used for
subnets
on an internal networks, and are controlled by a network administrator.
The
upper 48 bits
are used for the
global network addresses
and are for routing over the internet.
Address Types and Scope
IPv6 addresses have three types:
Global Unicast Address
–Scope Internet- routed on Internet
Unique Local
— Scope Internal Network or VPN internally routable, but
Not routed
on Internet
Link Local
– Scope network link-
Not Routed
internally or externally.
Global and Public Addresses
Global addresses are routable on the internet and start with
2001:
These addresses are known as
global Unicast addresses
and are the equivalent of the
public addresses
of IPv4 networks.
The Internet authorities allocate address blocks to ISPs who in turn allocate them to their customers. See
Global Address assignments
Internal Addresses- Link Local and Unique Local
In IPv4 internal addresses use the reserved number ranges
10.0.0.0/8, 172.16.0.0/12
and
192.168.0.0/16
and
169.254.0.0/16
.
These addresses are
not routed
on the Internet and are reserved for internal networks.
IPv6
also has
two Internal address types
.
Link Local
Unique Local
Link Local
These are meant to be used inside an internal network, and again they are
not routed
on the Internet.
It is equivalent to the IPv4 address
169.254.0.0/16
which is allocated on an IPv4 network when no DHCP server is found.
Link local addresses start with
fe80
They are restricted to a link and are
not routed
on the Internal network or the Internet.
Link Local addresses
are
self assigned
i.e. they do not require a
DHCP server.
A link local address is required on every IP6 interface even if no routing is present.
Unique Local
Unique Local
are meant to be used inside an internal network.
They are
routed
on the Internal network but
not routed
on the Internet.
They are equivalent to the IPv4 addresses are
10.0.0.0/8, 172.16.0.0/12
and
192.168.0.0/16
The address space is divided into two /8 spaces:
fc00
::/8 for globally assigned addressing, and
fd00
::/8 for locally assigned addressing.
For manually assignment by an organisation use the
fd00
prefix.
Using IPv6 Addresses in URLs
On IPv4 networks you can access a network rsource e.g. a web page using the format
http://192.168.1.21/webpage
However IPv6 addresses contain a colon as separator and so must be enclosed in square brackets.
http://[IPv6 address]/webpage.
IPv6 Loop Back
The IPv6 loopback address is ::1. You can ping it as follows:
Thank you all for the fine and informative to was IP V6, but I’m a beginner from a med laboratory technician, and I need to learn about this and I don’t have a computer, but I only have mobile phone android version,so how to go about it and how to create website address..
IPv6 will never replace IPv4 for the same reason that SNA and X.25 never took hold; it’s too difficult for many people to understand.. They made a huge mistake with ipV6; instead of adding a country and region byte to the header (which would have added enough addresses and also simplified routing and geo-location), the bearded geeks created a whole new entity.
I must admit I agree with you. Not about the solution as I’ve not really thought about it. Only that in my experience protocols upgrade and try to stay backwards compatible or not too drastic a change. Adding extra bits should not really have been a problem as it was done with MAC addresses.
Steve
Actually, that’s not entirely correct. SNA was all over the world however, it was privately developed by IBM for ue with their computing systems. Eventually SNA gateway to DLSW (SDLC/SNA over IP) as IP became more proliferate. X.25 was an international network transport standard (ITU) over which IP could be sent. While SNA was predominantly proprietary, X.25 was internationally accepted and could be considered a precursor to IP world-wide with international monitoring/maintenance of X.121 addressing to enable intercommunication. Both protocols were instrumental to help with the later widespread acceptance of IP and the Internet.
That is historically wrong. X.25 was the “standard” replacement for SNA, which was effectively dead in the late 80s. Siemens was peddling their X.25 switches in Europe and the US and the telcos were building a nationwide network; problem was that they had just been broken up and they were bickering over how to bill for traffic; that passed through multiple telcos. Meanwhile PSI slapped up a backbone and offered to the public what universities and the government had already been using on a nationwide basis with no per packet nonsense that the telcos wanted.
X.25 and SNA had nothing to do with “IP acceptance”. TCP/IP was accepted was because it was there, it worked and it was cheaper than what the telcos offered. Private industry effectively shot down X.25 (and ISDN) by solving a problem with something that is arguably better. X.25 switches had finite capacity issues that routers didn’t, so growth was much cheaper.
What I was referring to was before the internet, when X.25 switches were available but not yet widely deployed, companies would chose to put up SNA network even though they thought X.25 was better and knew that SNA had no future, because they couldn’t find enough engineers who knew X.25 to support a network
Isn’t it less confusing to say the 64 bits at the left or the 64 bits at the right rather than upper 64 bits or lower 64 bits? That was kind of confusing for me to grasp. Great work overall though. I understood everything once i got the upper 64 bits and lower 64 bits concept.
Actually, when saying upper and lower you are adding an extra piece of information, in that upper means higher order bits and lower means lower order bits. Left and right does not tell you this.
finally, a good site to check out whenever I have basic questions
btw I was wondering, since ipv6 is so vast that we could barely exhaust it, is there even a need to use ports?
or would ports be negligible/redundant in this case?
sorry I’m really not too deep into networking and don’t even know what /8/16/64 means; I just want to try and host a server but my isp doesn’t let me because all the ports are blocked
The protocol is designed to use ports the alternative would be that a network card had lots of addresses and how would you have the equivalent of well know ports e.g port 80 for a web server?
Steve
Ports help to tell a server that is receiving packets, which application to forward the packet contents to. For example, ssh uses well-known port 22 in the destination port. This tells the receiving computer that traffic with port 22 is going to the sshd application on the server. There could be multiple ssh sessions to the same computer but they all have the same destination port value of 22. The way the computer distinguishes multiple sessions going to the same port 22, is to also look at the source IP address and source port number for each packet. This way you can have multiple ssh sessions to the same server. You can also have multiple sessions using other ports (concurrently with multiple ssh sessions) be looking at all of this info concurrently.
/8 is called a prefix length
255.255.255.0 is called a mask
In IPv4 the number of bytes comprising the address is 4 shown as b1.b2.b3.b4. The mask is similar in that it also has 4 bytes, eg. 255.255.255.0 which happens to be same as /24. The 24 means that the first bits (higher order bits to the left) are all ones if you were to look at the mask as a binary representation:
/24 = 255.255.255.0 = 1111 1111.1111 1111.1111 1111.0000 0000
Prefix = Mask = Binary Representation of Mask
I used to have IPv6 connectivity, but now when I “View status of this connection” under “Change adapter options”, I only get “No network access”. I have tried resetting winsock catalog; resetting IPv6 log (netsh commands), to no avail. I’ve got a wrong setting somewhere under Wireless Properties” or the register. My ISP does provide IPv6. Help please! Will check other posts, since you may have answered this already. Win10 on Lenova Yoga920. Troubleshot and updated drivers, etc.
If you go to the adapter settings
Control Panel\Network and Internet\Network Connections
right click on the adapter and click on properties scroll down the list of check boxes until you find Internet protocol version 4 and make sure it is enabled.
Steve
What I consider an extremely elementary question about ipv6 that isn’t, as far as I can find, answered ANYWHERE, is how many common or garden variety numerical number of host addresses are in a /64 or /56. There are countless supposedly beginner tutorials on ipv6 but every single one goes on at length about bits and whatever and completely ignores the infinitely more relevant issue of the number of hosts. One of the very first things one finds in an ipv4 subnet is the common or garden variety numerical number of host addresses in a /28 or whatever. Why is is so difficult to use exactly the same logic with ipv6 ?
Don’t know but I can only assume that as there are lots of host addresses available it doesn’t seem a concern.
I Hope to revisit this tutorial at some point this year and update it and will give it some thought then.
Steve
its a 128-bit address. 64 of which is always the network identifier; 64 of which is always the host identifier. All networks (because they are by definition all /64) have (2^64)-1 host addresses, or more than 18 quintillion.
If you’re stuck in a subnetting/supernetting mindset, the math you need for P=Prefix -> Number of hosts is (2^(128-P))-1
There are 2^128 or 340 trillion, trillion, trillion IPv6 addresses, which is more than 100 times the number of atoms on the surface of the Earth. This will be more than sufficient to support trillions of Internet devices for the forseeable future. So in answer to your question, we don’t need to subnet like we did for IPv4. We subnetted and used NAT as a workaround because we didn’t have enough addresses before. Using /64 should always be fine. We will destroy the earth or kill ourselves before we run out.
Your video has helped me so much. Because of it I now have a life saving conversion table, which I did’nt know was out there.
Thank you for making it so much clearer
why did you delete my comment asking for clarity??
I am looking to see how you get the prefix fe80::/10 for link-local addresses beginning with fe80 to febf
“Global addresses are routable on the internet and start with 2001:”
Plenty of global addresses outside of 2001::/16 and have been since at least 2005. Follow the link you yourself supply to the list of allocations.
“If we look at the upper 64 bits in more detail we can see that it is split into 2 blocks of 48 and 16 bits respectively the lower 16 bits are used for subnets on an internal networks, and are controlled by a network administrator.”
This makes it sound as if /48 allocations are universal. They are merely common. The split between the size of the allocation and what is subnetted inside an AS is pretty arbitrary, though a nibble boundary is nice.
I think the ip6 URL example is wrong.
You have http:[IPv6 address]/webpage
I *think* it should be
http://[IPv6
address]/webpage. And if you need a port it goes as :port after the closing ] (ie
http://[IPv6
address]:port/webpage)
Finally, someone could explain in a short, 5 minutes read the whole IPv6 addressing schema without writing a university essay.
Thank you. So far the best and most valuable page on the Internet about the subject.
IPV6
has been developed to replace IPV4 which is