ipv6

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.