Setting up NAT Networking on Oracle Virtualbox on CentOS

First define a nat network under tools — preferences – network and give it a name, I called it NatNetwork.

 

Then right click on properties, and define the ip of the subnet – a new one just for NatNetwork, I chose 10.0.5.0

 

Next go to each VM and add a network adapter connected to NatNetwork

 

and select the network you created.

 

To enable IP packet forwarding please edit /etc/sysctl.conf with your editor of choice and set:
# Controls IP packet forwarding
net.ipv4.ip_forward = 1

You can then verify your settings with:
/sbin/sysctl -p

 

on each machine

 

sysctl -w net.ipv4.ip_forward=1

 

you also have to put it in the /etc/sysctl.d/sysctl.conf file! otherwise it does not take effect -and do:

 

root@router:/etc/netplan# sysctl –system

 

I did it with:

 

 

[root@clusterserver sysctl.d]# sysctl -w net.ipv4.ip_forward=1
net.ipv4.ip_forward = 1
[root@clusterserver sysctl.d]#

 

[root@clusterserver sysctl.d]# /sbin/sysctl -p
net.ipv4.ip_forward = 1
[root@clusterserver sysctl.d]#
root@router:/etc/netplan# sysctl –system

 

 

NOTE with centos and nmcli you have to first add a new connection:

 

[root@clusterserver network-scripts]# nmcli dev status
DEVICE TYPE STATE CONNECTION
enp0s3 ethernet connected enp0s3
enp0s8 ethernet connected enp0s8
virbr0 bridge connected (externally) virbr0
enp0s10 ethernet disconnected —
lo loopback unmanaged —
virbr0-nic tun unmanaged —

 

[root@clusterserver network-scripts]#
[root@clusterserver network-scripts]#
[root@clusterserver network-scripts]# nmcli con add type ethernet con-name enp0s10 ifname enp0s10 ip4 10.0.5.10
Connection ‘enp0s10’ (392ee518-be1b-4498-885c-cacef2e295d9) successfully added.
[root@clusterserver network-scripts]#

 

Unter CentOS a “connection” is not the same as a network interface, I have used the same name for the connection here, but it can be labeled differently.

 

then it looks like this:

 

[root@clusterserver network-scripts]#
[root@clusterserver network-scripts]# nmcli dev status
DEVICE TYPE STATE CONNECTION
enp0s3 ethernet connected enp0s3
enp0s10 ethernet connected enp0s10
enp0s8 ethernet connected enp0s8
virbr0 bridge connected (externally) virbr0
lo loopback unmanaged —
virbr0-nic tun unmanaged

 

Note that manual changes to the ifcfg file will not be noticed by NetworkManager until the interface is next brought up.

 

So, you have to do a

 

nmcli con down enp0s10 && nmcli con up enp0s10

 

[root@clusterserver network-scripts]# nmcli con down enp0s10 && nmcli con up enp0s10
Connection ‘enp0s10’ successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/5)
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/6)
[root@clusterserver network-scripts]#

 

To configure a static route for an existing Ethernet connection using the command line, enter a command as follows:
~]# nmcli connection modify eth0 +ipv4.routes “192.168.122.0/24 10.10.10.1”

 

This will direct traffic for the 192.168.122.0/24 subnet to the gateway at 10.10.10.1.

 

so, we need to do:

 

[root@clusterserver network-scripts]# nmcli connection modify enp0s10 +ipv4.routes “10.0.2.0/24 10.0.2.10”
[root@clusterserver network-scripts]#

 

Next, IMPORTANT!! do a reload of the specific connection:

 

[root@clusterserver network-scripts]# nmcli con reload enp0s10
[root@clusterserver network-scripts]#

 

otherwise the changes will not be active!

 

OR do interactively:

 

[root@clusterserver network-scripts]# nmcli con edit type ethernet con-name enp0s10

 

===| nmcli interactive connection editor |===

 

Adding a new ‘802-3-ethernet’ connection

 

Type ‘help’ or ‘?’ for available commands.
Type ‘print’ to show all the connection properties.
Type ‘describe [<setting>.<prop>]’ for detailed property description.

 

You may edit the following settings: connection, 802-3-ethernet (ethernet), 802-1x, dcb, sriov, ethtool, match, ipv4, ipv6, tc, proxy
nmcli> set ipv4.routes 10.0.5.0/24 10.0.5.10
nmcli>
nmcli>
nmcli> save persistent
Saving the connection with ‘autoconnect=yes’. That might result in an immediate activation of the connection.
Do you still want to save? (yes/no) [yes] yes
Connection ‘enp0s10’ (cbaf5c33-de4a-43a1-83af-7f51103706bd) successfully saved.
nmcli>

 

Setting up NAT NETWORK on Oracle VB on CentOS

 

first define a nat network under tools — preferences – network and give it a name, I called it NatNetwork

 

and then right click on properties, and define the ip of the subnet – a new one just for the nat network, I chose 10.0.5.0

 

next go to each VM and add a network adapter connected to NAT Network

 

and select the network you created.

 

To enable IP packet forwarding please edit /etc/sysctl.conf with your editor of choice and set:

 

# Controls IP packet forwarding
net.ipv4.ip_forward = 1
You can then verify your settings with:
/sbin/sysctl -p

 

on each machine

 

sysctl -w net.ipv4.ip_forward=1

 

you also have to put it in the /etc/sysctl.d/sysctl.conf file! otherwise it does not take effect -and do:

 

root@router:/etc/netplan# sysctl –system

 

I did it with:

 

 

[root@clusterserver sysctl.d]# sysctl -w net.ipv4.ip_forward=1
net.ipv4.ip_forward = 1

[root@clusterserver sysctl.d]#

 

[root@clusterserver sysctl.d]# /sbin/sysctl -p
net.ipv4.ip_forward = 1

[root@clusterserver sysctl.d]#
root@router:/etc/netplan# sysctl –system

 

 

NOTE with centos and nmcli you have to first add a new connection:

 

[root@clusterserver network-scripts]# nmcli dev status
DEVICE TYPE STATE CONNECTION
enp0s3 ethernet connected enp0s3
enp0s8 ethernet connected enp0s8
virbr0 bridge connected (externally) virbr0
enp0s10 ethernet disconnected —
lo loopback unmanaged —
virbr0-nic tun unmanaged —
[root@clusterserver network-scripts]#
[root@clusterserver network-scripts]#
[root@clusterserver network-scripts]# nmcli con add type ethernet con-name enp0s10 ifname enp0s10 ip4 10.0.5.10
Connection ‘enp0s10’ (392ee518-be1b-4498-885c-cacef2e295d9) successfully added.
[root@clusterserver network-scripts]#

 

Unter CentOS a “connection” is not the same as a network interface, I have used the same name for the connection here, but it can be labeled differently.

 

then it looks like this:

 

[root@clusterserver network-scripts]#
[root@clusterserver network-scripts]# nmcli dev status
DEVICE TYPE STATE CONNECTION
enp0s3 ethernet connected enp0s3
enp0s10 ethernet connected enp0s10
enp0s8 ethernet connected enp0s8
virbr0 bridge connected (externally) virbr0
lo loopback unmanaged —
virbr0-nic tun unmanaged

 

Note that manual changes to the ifcfg file will not be noticed by NetworkManager until the interface is next brought up.

 

So, you have to do a

 

nmcli con down enp0s10 && nmcli con up enp0s10

 

[root@clusterserver network-scripts]# nmcli con down enp0s10 && nmcli con up enp0s10
Connection ‘enp0s10’ successfully deactivated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/5)
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/6)
[root@clusterserver network-scripts]#

 

 

To configure a static route for an existing Ethernet connection using the command line, enter a command as follows:
~]# nmcli connection modify eth0 +ipv4.routes “192.168.122.0/24 10.10.10.1”
This will direct traffic for the 192.168.122.0/24 subnet to the gateway at 10.10.10.1.

 

so, we need to do:

 

[root@clusterserver network-scripts]# nmcli connection modify enp0s10 +ipv4.routes “10.0.2.0/24 10.0.2.10”
[root@clusterserver network-scripts]#

 

Next, IMPORTANT!! do a reload of the specific connection:

 

[root@clusterserver network-scripts]# nmcli con reload enp0s10
[root@clusterserver network-scripts]#

 

otherwise the changes will not be active!

 

OR do interactively:

 

[root@clusterserver network-scripts]# nmcli con edit type ethernet con-name enp0s10

 

===| nmcli interactive connection editor |===

 

Adding a new ‘802-3-ethernet’ connection

Type ‘help’ or ‘?’ for available commands.
Type ‘print’ to show all the connection properties.
Type ‘describe [<setting>.<prop>]’ for detailed property description.

 

You may edit the following settings: connection, 802-3-ethernet (ethernet), 802-1x, dcb, sriov, ethtool, match, ipv4, ipv6, tc, proxy
nmcli> set ipv4.routes 10.0.5.0/24 10.0.5.10
nmcli>
nmcli>
nmcli> save persistent
Saving the connection with ‘autoconnect=yes’. That might result in an immediate activation of the connection.
Do you still want to save? (yes/no) [yes] yes
Connection ‘enp0s10’ (cbaf5c33-de4a-43a1-83af-7f51103706bd) successfully saved.
nmcli>