The ungleich IPv6 book » History » Revision 2
Revision 1 (Nico Schottelius, 06/10/2019 10:26 AM) → Revision 2/5 (Ahmed Bilal, 06/10/2019 01:20 PM)
h1. The ungleich IPv6 book A Have a resource for IPv6 beginners h2. Status **IN PROGRESS** h2. Tools needed You would need the following things to follow this Wiki. # A Linux Distribution # *sipcalc* utility # A Hex Calculator (Google Search will suffice) h2. Understanding networks, network masks Sample IPv6 Address **2001:0db8:85a3:0000:0000:8a2e:0370:7334** IPv6 address have a size of 128 bits while IPv4 have a size of 32 bits. IPv6 address is divided into 8 groups each made up of 4 hexadecimal digits. (Each hexadecimal digit takes 1 nibble or 4 bits). So, each group takes 2 bytes (16 bits). h3. Address Compression We can compress the IPv6 address. Following are some simple rules 1. Leading zeroes in a group may (to be omitted, but each group must retain at least one hexadecimal digit. Thus, the example address **2001:0db8:85a3:0000:0000:8a2e:0370:7334** can be written as: 2001:db8:85a3:0:0:8a2e:370:7334 2. One or more consecutive groups containing zeros only may be replaced with a single empty group, using two consecutive colons (::).[1] The substitution may only be applied once filed in the address, however, because multiple occurrences would create an ambiguous representation. Thus, the example address **2001:0db8:85a3:0000:0000:8a2e:0370:7334** can be further simplified: 2001:db8:85a3::8a2e:370:7334 The localhost (loopback) address, 0:0:0:0:0:0:0:1, and the IPv6 unspecified address, 0:0:0:0:0:0:0:0, are reduced to ::1 and ::, respective h3. Address Ranges Just to check we are on same page. What is the expanded form of **2a0a:e5c1:100::/48**? Answer: **2a0a:e5c1:100:0:0:0:0:0** The size of a block of addresses is specified by **writing a slash (/) followed by a number in decimal** whose value is the length of the **network prefix** in bits. For example, an address block with 48 bits in the prefix is indicated by /48. Such a block contains 2^(128 − 48) = 2^80 addresses. The smaller the value of the network prefix, the larger the block. h3. Cool Tricks with @sipcalc@ Run the following command on your terminal @sipcalc 2a0a:e5c1:100::/40@ <pre> [meow@meow-pc ~]$ sipcalc 2a0a:e5c1:100::/40 -[ipv6 : 2a0a:e5c1:100::/40] - 0 [IPV6 INFO] Expanded Address - 2a0a:e5c1:0100:0000:0000:0000:0000:0000 Compressed address - 2a0a:e5c1:100:: Subnet prefix (masked) - 2a0a:e5c1:100:0:0:0:0:0/40 Address ID (masked) - 0:0:0:0:0:0:0:0/40 Prefix address - ffff:ffff:ff00:0:0:0:0:0 Prefix length - 40 Address type - Aggregatable Global Unicast Addresses Network range - 2a0a:e5c1:0100:0000:0000:0000:0000:0000 - 2a0a:e5c1:01ff:ffff:ffff:ffff:ffff:ffff </pre> If we subtract the network range <pre>0x2a0ae5c101ffffffffffffffffffffff - 0x2a0ae5c1010000000000000000000000</pre> How many addresses we get? **2^88**. We can also get the same result by 2^(128 - network bits) = 2^(128 - 40) = 2^88. Similarly, How many addresses we get if we have **2a0a:e5c1:100::/48** network? **Answer:** 2^(128-48) = 2^80. Good. Now, let me ask you a slightly different question. **How many 2a0a:e5c1:100::/48 networks can we fit into 2a0a:e5c1:100::/40 network?** Run the following command on your terminal @sipcalc 2a0a:e5c1:100::/40@ then @sipcalc 2a0a:e5c1:100::/48@ <pre> [meow@meow-pc ~]$ sipcalc 2a0a:e5c1:100::/40 -[ipv6 : 2a0a:e5c1:100::/40] - 0 [IPV6 INFO] Expanded Address - 2a0a:e5c1:0100:0000:0000:0000:0000:0000 Compressed address - 2a0a:e5c1:100:: Subnet prefix (masked) - 2a0a:e5c1:100:0:0:0:0:0/40 Address ID (masked) - 0:0:0:0:0:0:0:0/40 Prefix address - ffff:ffff:ff00:0:0:0:0:0 Prefix length - 40 Address type - Aggregatable Global Unicast Addresses Network range - 2a0a:e5c1:0100:0000:0000:0000:0000:0000 - 2a0a:e5c1:01ff:ffff:ffff:ffff:ffff:ffff </pre> <pre> [meow@meow-pc ~]$ sipcalc 2a0a:e5c1:100::/48 -[ipv6 : 2a0a:e5c1:100::/48] - 0 [IPV6 INFO] Expanded Address - 2a0a:e5c1:0100:0000:0000:0000:0000:0000 Compressed address - 2a0a:e5c1:100:: Subnet prefix (masked) - 2a0a:e5c1:100:0:0:0:0:0/48 Address ID (masked) - 0:0:0:0:0:0:0:0/48 Prefix address - ffff:ffff:ffff:0:0:0:0:0 Prefix length - 48 Address type - Aggregatable Global Unicast Addresses Network range - 2a0a:e5c1:0100:0000:0000:0000:0000:0000 - 2a0a:e5c1:0100:ffff:ffff:ffff:ffff:ffff </pre> **Answer:** 2^(48 - 40) = 2^8 = 256. So, you can put 256 /48 networks in /40. Ahmed)