In this section we're going to be talking about IPv6 addresses. IPv6 addresses are 128-bit binary numbers. If you have 128 bits how many unique addresses are you going to have in total? Remember with binary mathematics you're going to have 2 to the power of 128 bits which is equals to 3.40 times 10 to the power of 38 number of possible IPv6 addresses. IPv6 addresses are conventionally represented in hexadecimal this is eight words of 16 bits remember that 128 bits is a very large number to remember so we represent it using hexadecimal numbers as you can see on the screen this is a typical ipv6 address it's um represented as 2607 colon 8400 column 2880 column zero zero zero four one zero zero zero zero one one zero zero zero zero column eighty d f colon ninety one three leading zeros can be dropped in hexadecimal numbers the largest contiguous run of all zero words can also be replaced as you can see with the example zero zero zero four can be represented by four you see eight zeros can also be represented by double colon so you see that the ipv6 number that we provided can be shortened in the form of seven colon eight four zero zero column two eight eight zero column four then you have double column represented the eight zeros followed by atd f colon ninety one three we're going to show you a brief representation of how you convert binary to hexadecimal remember that hexadecimal is base 16. binary is base 2. so with hexadecimal numbers you're going to have numbers from 0 all the way to f 10 is represented by a 11 is represented by b 12 is represented by c 13d 14e and f as you can see on the screen zero in hexadecimal to binary is zero zero zero zero one is zero zero zero one and so on you see that e is one one one zero and f is one one one one so you can use this sheet to figure out how to convert from binary to hexadecimal so what are the IPv6 rules with IPv6. Every subnet is a slash 64 with the exception of slash 127 which is also used for point-to-point links. In this case the remaining 64-bits can be assigned by hand or picked automatically remember all zero address is reserved remember when we were doing IPv4 all zero addresses were reserved for network addresses in this case it's for ipv6 is for subnet router any case address with the exception of course this is slash 127 which is a 0.1 point to point link which only has two ip addresses and you can use zero zero zero in that case there are also some special prefixes in ipv6 we did not cover those in ipv4 but you have some pressure prefixes one of them is a link local address which starts with fe 80 double column you have approximately 2 to the power of 61 subnets in IPv6 space which is more than we can use as we're running out of IPv4 addresses which is why we move to IPv6 addresses. What does a typical end user allocation in IPv6 addressing look like? The typical end user allocation is a slash 48. As you can see you have 128 bits for the IPv6 number so you would preserve the 464 bits for the network prefix like we said in the previous slide that all addresses are slash 64 and the host bit would have 64 bits as well so a typical end user allocation is a slash 48 so now we ask the question how many 64 networks can you build from a slash 48 allocation remember we're using bits so it's still the same binary mathematics that you applied in IPv4 that you will be using in ipv6 we'll show you briefly if you have 128 bits and you have a slash 48 allocation how many bits are going to have remaining you will have 128 minus 64 minus 48 which will give you 16 bits so the number of networks like 64 networks in the slash 48 prefix is going to be 2 to the power of 16 which will give you 65 536 now imagine you are assigned the ipv6 prefix 2001 colon db8 colon 123 double colon slash 48 this is represented on the screen as 2001 zero db eight colon zero one two three column followed by all zeros what is the lowest life 64 network that you can get from this slash 48 prefix remember that you have 16 bits in this case for the slash 64 prefix as we had shown you in the previous slide so the lowest network of slash 64 prefix that you're going to get is going to be 2 0 0 1 colon db 8 colon 1 2 3 colon 0 0 0 0 as shown in red double colon followed by a slice 64. this is simply written as 2 0 0 1 colon bb 8 colon 1 2 3 double colon slash 64. remember that all zeroes are represented by double column the highest life 64 network you're going to get is going to be 2 0 0 1 column db 8 column 1 2 3 colon fff double colon slash 64. remember you have 16 bits for the number of networks in this case as shown in the previous slide how many ways do you have of allocating the host part the first option is that you have is that you can do it automatically from the mac address which is called statelet auto configuration this is not recommended for servers because if you change the nic address the ipv6 address will change you can also number sequentially from one and use the last octet of the ipv4 address the third option that you have is you can embed the whole ipv4 address inside of the ipv6 address an example is shown on the screen you have this address 2607 call on eight four zero zero column two eight eight zero column four double column attf colon ninety thirteen you can see that the last two words are simply the ipv4 address converted to hexadecimal in this case the ipv4 address is 18.104.22.168 in decimal if you convert this to hex you're going to have 80 for 128 223 is represented by df 157 is represented by 90 and 19 is represented by 13 in hexadecimal alternatively you can actually write the IPv4 address inside of the IPv6 address as shown on the screen so we're going to give you notes on IPv6 it's broadly similar to IPv4. The concepts are the same. Remember it's still binary. We're just representing the numbers in hexadecimal to make it easier to remember and write r is replaced by ndp in this case and you have various forms of IPv6 client configuration options like we had shown on the previous slide the first one is the stateless configuration using router advertisements or you can use stateless auto configuration plus stateless DHCP version 6 or you can use stateful DHCP version 6. interfaces typically get both a link local address and one or more routable prefixes when you're using IPv6 you typically have a dual stack which means you're using both IPv4 and IPv6 signed by software.
© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.
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