IPv6 Subnetting

From Internetworkpro

Contents 1 Overview 1.1 Global Routing Prefix 2 General Scheme 2.1 Router Loopback Addresses 2.2 Point-to-Point Addresses 2.3 Server Subnets 2.4 General End-Node Subnets

[edit] Overview

This document describes a possible best practices IPv6 addressing scheme that can be used on a campus LAN. This is by no means the only way to subnet your IPv6 network, but it serves as a general guideline.

[edit] Global Routing Prefix

An organization is often allocated a /48 block of IPv6 address space. For this document, we will be using 2001:DB8:1::/48

The structure of an IPv6 address looks like the following (see RFC 3513):

   |         n bits (48)     |m bits (16)|       128-n-m bits (64)    |
   +-------------------------+-----------+----------------------------+
   | global routing prefix   | subnet ID |       interface ID         |
   +-------------------------+-----------+----------------------------+

where the global routing prefix is our 2001:DB8:1::

[edit] General Scheme

The /48 would then be split into 65536 /64s, with the first /64 reserved (0000) for loopback addresses:

2001:DB8:1:0000:0000:0000:0000:0000/64

[edit] Router Loopback Addresses

Router loopback addresses are /128 bit host routes allocated from the prefix 2001:DB8:1:0000:0000:0000:0000:0000/64

Each router loopback address is indicated by its Router # (y):

2001:DB8:1:0000:0000:0000:0000:0001/128
2001:DB8:1:0000:0000:0000:0000:0002/128
...
2001:DB8:1:0000:0000:0000:0000:FFFE/128
2001:DB8:1:0000:0000:0000:0000:FFFF/128

For example, lo0 on Router 15 would be: 2001:DB8:1::15/128

[edit] Point-to-Point Addresses

Point-to-Point subnets are links between only two nodes.
For such networks, we could use one specific set of networks allocated from the prefix 2001:DB8:1:F000:0000:0000:0000:0000/52

These are exmamples of possible Point to Point subnets:

2001:DB8:1:F001:0000:0000:0000:0001/64
2001:DB8:1:F001:0000:0000:0000:0002/64
...
2001:DB8:1:FFFF:0000:0000:0000:0001/64
2001:DB8:1:FFFF:0000:0000:0000:0002/64

[edit] Server Subnets

Server subnets are anything that is not an end node subnet, typically servers.
For such networks, we could use one specific set of networks allocated from the prefix 2001:DB8:1:A000:0000:0000:0000:0000/52

These are examples of possible server subnets:

2001:DB8:1:A001:0000:0000:0000:0000/64
2001:DB8:1:A002:0000:0000:0000:0000/64
...
2001:DB8:1:AFFE:0000:0000:0000:0000/64
2001:DB8:1:AFFF:0000:0000:0000:0000/64

[edit] General End-Node Subnets

There are two ways you could subnet your end node subnets:

   |         n bits (48)     | b(8) | s(8) |       128-b-s bits (64)    |
   +-------------------------+-------------+----------------------------+
   | global routing prefix   | bldg | srvc |       interface ID         |
   +-------------------------+-------------+----------------------------+

OR

   |         n bits (48)     |    v(16)    |       128-v bits (64)    |
   +-------------------------+-------------+----------------------------+
   | global routing prefix   |   VLAN ID   |       interface ID         |
   +-------------------------+-------------+----------------------------+

Building addresses are summarized as: 2001:DB8:1:bb00:0000:0000:0000:0000/56

Service addresses are: 2001:DB8:1:bbss:0000:0000:0000:0000/64

Therefore, Building 13, Service 10 (Faculty Staff) would be: 2001:DB8:1:1310::/64