Added Bird and general routing documentation (WIP)

docs/bird_basics.md

@@ -0,0 +1,35 @@
+Basics
+======
+
+## Installing bird
+
+Installation of bird is relatively simple, your distro should have a `bird` package.
+
+Versions 1.6 and 2.0 will both work, there are slight differences in the configuratio
+however but those will be shown in the configuration section that follows.
+
+## Enabling forwarding
+
+We will be setting up the machine that runs bird as a router so therefore
+we need to make your Linux kernel's network stack not drop IPv6 packets
+that it receives (addressed to it via Ethernet) but are not addressed to
+it via IPv6 address - in other words it must try do something with these packets,
+namely attempt to forward them one hop closer to their initial destination.
+
+Enabling forwarding on all interfaces can be achieved as follows (you will need
+to be root):
+
+```bash
+echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
+```
+
+However, after reboot it won't be saved and will go back to its defaults. Therefore
+what you need to do is to enable forwarding on boot-up, this can be done by
+adding an additional line to your `/etc/sysctl.conf` (which holds a bunch of
+these statements), it should look like this:
+
+```bash
+sys.net.ipv6.conf.all.forwarding=1
+```
+
+TODO: Weird experience with me, only doing `all` made it work

docs/routing.md

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+Setting up routing
+==================
+
+There are 3 methods (so far) of doing routing on CRXN, we list them
+below each with their corresponding setup procedures. The recommended
+procedure is, however, using Bird.
+
+1. [Bird](bird)

mkdocs.yml

@@ -6,6 +6,14 @@ nav:
   - Getting started:
       - Guide: getting-started.md
       - Rules: rules.md
+      - Requirements: requirements.md
+      - Assigning subnet: prefixes.md
+      - Routing:
+         - Introduction: routing.md
+         - Bird-based routing:
+            - Basics: bird_basics.md
+         - Babeld-based routing
+         - Mikrotik-based routing
   - Tutorial:
       - Peering: peering.md
       - CRXNv6: crxnv6.md