The ungleich IPv6 book » History » Revision 3
Revision 2 (Ahmed Bilal, 06/10/2019 01:20 PM) → Revision 3/5 (Ahmed Bilal, 06/10/2019 01:22 PM)
h1. The ungleich IPv6 book
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 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 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.
h2. References
* https://en.wikipedia.org/wiki/IPv6_address