> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ck-itsolutions.nl/llms.txt
> Use this file to discover all available pages before exploring further.

# GRE Setup Network Bridge

> This guides shows how to use Remote IPv4 IPs, tunnelled via GRE to your hypervisor and use the IPs on your VMs.

### General Information

IP block we want to use on server B: `171.32.42.128/29`

Internal IP Block used for communication: `10.0.0.0/30`

Bridge interface server B: `br0`

### Server B

1. Setup the GRE tunnel on server B.

```
ip tunnel add gre1 mode gre local <IP server B> remote <IP server A> ttl 255
ip addr add 10.0.0.2/30 dev gre1
ip link set gre1 up
```

2. Enable IP forwarding. **\[only execute once]**

```
sudo modprobe ip_gre
lsmod | grep gre
sudo apt install iptables iproute2
sudo echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
sudo sysctl -p
```

3. Route data from the GRE tunnel to the bridge and back.

```
ip route add default dev gre1 table 3
ip rule add from 171.32.42.128/29 table 3
ip route add 171.32.42.128/29 dev br0 table 3
ip addr add 171.32.42.128/29 dev br0 (If not already added to the bridge via netplan config)
```

You should be able to ping server A from server B.

```
Ping Server A
ping 10.0.0.1
```

To configure netplan, save configuration files under `/etc/netplan/` with a `.yaml` extension (e.g. `/etc/netplan/config.yaml)`,
then run `sudo netplan apply`. This command parses and applies the configuration to the system. Configuration written to disk under `/etc/netplan/` will persist between reboots.
Example file contents : `/etc/netplan/01-netcfg.yaml`

**Note:** *You will need the bridge-utils package installed on your server*

4. Add the following lines to the netplan file on the same level as "ethernets"

```
bridges:
  br0:
    addresses: ["171.32.42.129/29"]
```

Use the following network config in the adapter of your VM:

```
IP address: 191.80.60.130
Mask: 255.255.255.248 (depends on the subnet)
Gateway: 171.32.42.129
```

<Tip>We recommend setting the MTU of the bridge / VM network interface to **1476** as otherwise packet fragmentation may occur.</Tip>

That's it! Configure the network bridge and IPs in Virtfusion. On a server restart all the things we did will be wiped out. To make sure the GRE tunnel and everything else is going to work after a restart we have to edit the file `/etc/rc.local` and add all the commands we did (except for the echo ones!) before the `exit 0`.