Added Oracle Cloud ipv6 docs configuration

docs/configuration/ipv6/oraclecloud.md

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+---
+description: How to configure IPv6 on your Oracle Cloud VPS.
+---
+
+## Setting up IPv6 on Oracle Cloud using TunnelBroker Tunnel (48 oraz 64 block)
+
+This guide will assist you in setting up an IPv6 tunnel using Tunnelbroker.net. The steps provided are tested on Ubuntu (20.04 but works with other versions also).
+
+## 1st step
+`For this step, it is recommended to have knowledge of configuring and connecting to the instance using SSH or another protocol.` 
+
+**If you do not have the knowledge yet, reffer to this [article](https://docs.oracle.com/en-us/iaas/Content/Compute/Tasks/launchinginstance.htm) or this [video](https://www.youtube.com/watch?v=89CVSTPjfCc).**
+- Go to [cloud.oracle.com](https://cloud.oracle.com/)
+- Create **new Instance (VM)**. Shape doesn't matter. *(I use Ampere A1.Flex)*
+
+  **Note:** If you get an error `Out of the capacity`, there's nothing you can do but wait and try again in few days. It's frustrating, but it's Oracle.
+- For a tested and correct configuration, it is recommended to set the Image to `Ubuntu`. As it was previously stated: *version doesn't matter*. Just be sure it's `>=20.04`.
+
+
+## 2nd step
+`Follow this step if your instance is already running.`
+#### This step provides us with a possible server response from TunnelBroker, to which we will add our ip. This is discussed in the #4th step. 
+- Go to the main page of your Instance and click on the `Subnet`.
+
+![image](https://github.com/user-attachments/assets/26a3fd3e-0e15-43dc-a397-52874d0f5c3b)
+
+- Click on the `Default Security List for your Virtual Cloud Network`.
+
+![image](https://github.com/user-attachments/assets/d1224ea0-3fb9-4356-a753-7b768d895cf9)
+
+- Click on `Add Ingress Rules`.
+
+![image](https://github.com/user-attachments/assets/df0ee418-64a9-4b6b-9811-7145fe470973)
+**Note**: As you can see, I already have the `ICMP IP Protocol` configured. But I will walk you through.
+- The pop-up will show:
+
+![image](https://github.com/user-attachments/assets/641c0883-9437-42fa-9d3a-49f5ac7330a3)
+
+Configure it accordingly:
+- For `Source CIDR` type: **0.0.0.0/0**
+- For `IP Protocol` change to: **ICMP**
+So your fully configured `Ingress Rule` should look like this:
+
+![image](https://github.com/user-attachments/assets/ef467326-05e2-4f3a-ac30-ae33726b66f4)
+
+- Click `Save changes`.
+
+
+## Step 3
+
+#### Enabling IPv6 Non-Local Bind
+
+Before proceeding with the tunnel setup, it's recommended to enable IPv6 non-local bind. This allows applications to bind to non-local addresses.
+On your configured and connected instance execute the following commands:
+```bash
+# Enable now
+sysctl -w net.ipv6.ip_nonlocal_bind=1
+# Persist for next boot
+echo 'net.ipv6.ip_nonlocal_bind = 1' >> /etc/sysctl.conf
+# (Optionally) Load in sysctl settings from the file specified or /etc/sysctl.conf if none given.
+sysctl -p
+```
+
+## Step 4
+
+### Register on Tunnelbroker.net:
+
+1. Go to [Tunnelbroker.net](https://www.tunnelbroker.net).
+2. Sign up for an account if you haven't already.
+3. Log in to your account.
+
+### Create a Tunnel:
+
+1. After logging in, [Create Tunnel](https://tunnelbroker.net/new_tunnel.php).
+2. Enter your IPv4 endpoint (your public IPv4 address).
+- Can be obtained from the main instance page:
+![image](https://github.com/user-attachments/assets/99c79cf0-2ea6-4fcb-82af-421d04df10da)
+**Note**: It should already be *pingable* and Tunnelbroker should give us the info: `Possible Tunnel` or something like that. Green info message.
+4. Select the nearest server to your location (physical, not the location of the instance).
+- Fully configured tunnel should look like that:
+![image](https://github.com/user-attachments/assets/aa682b33-b110-44f6-9525-ab0ca88aa467)
+
+5. **Optionally**: Click on **Assign /48** to use `/48 block`. It is less likely to be blocked.
+![image](https://github.com/user-attachments/assets/20f70ae5-bdb7-4566-83f9-7e171cd5e1d1)
+
+
+### Configuration:
+This step is done already at the server.
+
+#### Command 1: Add IPv6 Tunnel Interface
+
+```bash
+sudo ip tunnel add he-ipv6 mode sit remote [TUNNEL_SERVER_IPV4] local [YOUR_CLIENT_IPV4] ttl 255
+```
+
+- Replace `[TUNNEL_SERVER_IPV4]` with the server's IPv4 address provided by Tunnelbroker.net.
+
+![image](https://github.com/user-attachments/assets/e4ec08e3-134e-4828-9a60-668b1b9d5f8c)
+
+- Replace `[YOUR_CLIENT_IPV4]` with your server's IPv4 address. We are using Oracle, so we need to replace it by using `Private IPv4 Address` obtained from the main page of the instance.
+
+![image](https://github.com/user-attachments/assets/0c583a08-4a41-46a3-bb51-4c656a20aa28)
+
+
+**Note**: If you encounter the "no buffer space available" error during this step due to misconfiguration, run:
+
+```bash
+sudo ip tun del he-ipv6
+```
+- Replace `he-ipv6` with the name of the interface you initially set up. You can check your current interfaces using `ifconfig`.
+
+#### Command 2: Set up IPv6 Tunnel Interface
+
+```bash
+sudo ip link set he-ipv6 up
+```
+
+- This command brings the IPv6 tunnel interface up.
+
+#### Command 3: Add IPv6 Address to the Tunnel Interface
+
+For **/48** block:
+```bash
+sudo ip addr add [YOUR_IPV6_BLOCK]::2/48 dev he-ipv6
+```
+
+For **/64** block:
+```bash
+sudo ip addr add [YOUR_IPV6_BLOCK]::2/64 dev he-ipv6
+```
+
+- This assigns an IPv6 address to the tunnel interface.
+- Replace `[YOUR_IPV6_BLOCK]` with your allocated **IPv6 block**. This one can be obtained from the Tunnelbroker tunnel which we previously created:
+
+![image](https://github.com/user-attachments/assets/dfda7f3e-1c91-4378-b6fe-91a1f06ae7b5)
+
+**Important note**: `Ipv6 block` isn't the whole address. It's the *block*. So for example:
+- We have the `Routed /64` assigned as `2001:470:72:5e::/64`.
+- The `block` we want to copy is: `2001:470:72:5e`.
+- The same thing for `/48` one.
+
+
+#### Command 4: Add IPv6 Default Route
+
+```bash
+sudo ip route add ::/0 via [YOUR_IPV6_BLOCK]::1 dev he-ipv6
+```
+
+- This command adds a default route for IPv6 traffic via the tunnel interface.
+- If you encounter a **"File exists"** error, change `add` to `replace`
+- Replace `[YOUR_IPV6_BLOCK]` with the previously mentioned block.
+
+#### Command 5: Handle Limited Pingability
+
+For **/48 block**:
+```bash
+sudo ip -6 route replace local [YOUR_IPV6_BLOCK]::/48 dev lo
+```
+
+For **/64 block**:
+```bash
+sudo ip -6 route replace local [YOUR_IPV6_BLOCK]::/64 dev lo
+```
+
+- This command ensures that traffic destined for addresses within your `/48` or `/64` block is routed correctly.
+
+### Testing 
+
+```bash
+ping6 -I [YOUR_IPV6_BLOCK]::4 google.com
+```
+- This command pings `google.com` using the IPv6 address `[YOUR_IPV6_BLOCK]::4` as the source address.
+
+```bash
+ping6 -I [YOUR_IPV6_BLOCK]::3 google.com
+```
+- This command pings `google.com` using the IPv6 address `[YOUR_IPV6_BLOCK]::3` as the source address.
+
+```bash
+ping6 -I [YOUR_IPV6_BLOCK]::2 google.com
+```
+- This command pings `google.com` using the IPv6 address `[YOUR_IPV6_BLOCK]::2` as the source address.
+- If the `ping6` using `::2` is the only one that works, refer to commands 4 and 5 for solution. 
+
+These commands allow you to test connectivity to `google.com` using different IPv6 source addresses. Adjust the source addresses as needed for your testing purposes.