{{tag>linux ipv6}}
======IPv6 summary notes======
Largely taken from 
  *[[https://github.com/onemarcfifty/cheat-sheets/blob/main/networking/ipv6.md|onemarcfifty]]
  *[[https://zivaro.com/what-you-need-to-know-about-ipv6-link-local-addresses/|What You Need to Know about IPv6 Link-Local Addresses]]
====Address length and format====

The IPv6 address is 128 bits (i.e. 16 bytes) long and is written in 8 groups of 2 bytes in hexadecimal numbers separated by colons:
<code>FDDD:F00D:CAFE:0000:0000:0000:0000:0001

Leading zeros of each block can be omitted, the above address can hence be written like this:
FDDD:F00D:CAFE:0:0:0:0:1

We can abbreviate whole blocks of zeros with :: and write:
FDDD:F00D:CAFE::1

This can only be done once in order to void ambiguity:
FF:0:0:0:1:0:0:1 (correct)
FF::1:0:0:1 (correct)
FF:0:0:0:1::1 (correct)
FF::1::1 (ambiguous, wrong)</code>

====Protocols====
|<30em 20px 70px >|
^Number	^Protocol^	Purpose^
|58	|IPv6-ICMP|	Information, Error reporting, diagnostics-
|6	|TCP|	Stateful - controls if packets arrived|
|17	|UDP|	Stateless - streaming applications etc.|

Ways to assign IPv6 addresses:
  *Static - fixed address
  *SLAAC - Stateless Address Autoconfiguration (host generates itself)
  *DHCPv6 - Dynamic host configuration protocol (assigned by central server)

====Scopes and special addresses====
  *GLOBAL - everything (i.e. the whole internet)
  *UNIQUE LOCAL - everything in our LAN (behind the internet gateway)
  *LINK LOCAL - (will never be routed, valid in one collision domain, i.e. on the same switch)

|<330px 80px >|
^range ^Purpose^
|::1/128  |Loopback address (localhost)|
|::/128	|unspecified address|
|2000::/3  |GLOBAL unicast (Internet)|
|FC00::/7  |Unique-local (LAN), note 1|
|FE80::/10   |Link-Local Unicast (same switch)|
Notes:
  -Unique local is actually FD00::/8 and is generally not recommended nor needed for small networks
  -Always use the smallest possible scope for communication
  -A host can have multiple addresses in different scopes

====Subnetting====
|<40em 30px 50px>|
|bits (MSB)	|Purpose|
|First 48 bits:	|Network address|
|Next 16 bits:	|Subnet address|
|Last 64 bits:	|Device address|
Network+Subnet = Prefix

The following address

2003:1000:1000:1600:1234::1
would have the network 2003:1000:1000, the subnet 1600, so together the prefix 2003:1000:1000:1600. If the ISP provider delegated a part of the prefix to me (e.g. 2003:1000:1000:1600/56) then I could use the subnets from 2003:1000:1000:1600 to 2003:1000:1000:16FF for my own purposes (i.e. define 256 subnets in this example)

IPv6 addresses in URIs/URLs

Because IPv6 address notation uses colons to separate hextets, it is necessary to encase the address in square brackets in URIs. For example %%http://[2a00:1450:4001:82a::2004]%%. If you want to specify a port, you can do so as normal using a colon: %%http://[2a00:1450:4001:82a::2004]:80%%.

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