Table of Contents

General description

It is strongly recommended to use only physical network adapters for CHARON-AXP networking to gain maximum performances. In situations where the host has only one network adapter, you can use Linux virtual network Interfaces ("TUN/TAP") and map individual CHARON-AXP instances to their own virtual interfaces.

There are 2 ways to create the Linux virtual network Interfaces ("TUN/TAP"):

• Using the "ncu" utility
• Manually

Using "ncu" utility to establish CHARON virtual network

Login as root and start the "ncu" utility:

CHARON Network Configuration Utility,  Version 1.6. Copyright (C) 2014-2019 STROMASYS SA. 
 
Interfaces Dedicated to State 
---------- ------------ ----- 
eth0 host connected to host 
eth1 host disconnected from host 
lo host unmanaged from host 
================================================================= 
bridge name bridge id STP enabled interfaces 
========================== VLAN ================================= 
================================================================= 
 select action: 
1 - Dedicate to CHARON 
2 - Release to host 
3 - Create Bridge with TAPs 
4 - Remove Bridge 
5 - Add VLAN 
6 - Remove VLAN 
7 - Print status 
8 - Exit

Enter "3" to create a bridge between the host physical network adapter and the Linux virtual network interfaces (TAP) and specify the physical network interface ("eth1" in our example) and the number of virtual network interfaces to be created (2 in our example):

 select action: 
1 - Dedicate to CHARON 
2 - Release to host 
3 - Create Bridge with TAPs 
4 - Remove Bridge 
5 - Add VLAN 
6 - Remove VLAN 
7 - Print status 
8 - Exit

Now enter "7" to see the created virtual interfaces:

Interfaces Dedicated to State 
---------- ------------ ----- 
eth0 host connected to host 
eth1 bridge disconnected from bridge 
lo host unmanaged from host 
tap0 CHARON connected to host 
tap1 bridge connected to bridge 
================================================================= 
bridge name    bridge id           STP enabled   interfaces 
br0_eth1       8000.22314588acac   no            eth1 
                                                 tap0 
                                                 tap1 
========================== VLAN ================================= 
================================================================= 
 
 select action: 
1 - Dedicate to CHARON 
2 - Release to host 
3 - Create Bridge with TAPs 
4 - Remove Bridge 
5 - Add VLAN 
6 - Remove VLAN 
7 - Print status 
8 - Exit

In the example above we see 2 virtual network interfaces, "tap0" and "tap1", connected to the created bridge. The physical network interface "eth1" is used for the bridge to the virtual network interfaces.

The interfaces "tap0" and "tap1" are ready to be used in CHARON configurations, they do not need to be additionally dedicated to CHARON.

Enter "8" to quit the "ncu" utility.

Manual configuration of CHARON virtual network

Host preparation

1. Login as "root" user.
   
   

2. Configure the physical network interface to run in promiscuous mode using the following command. This interface will be dedicated to the whole network bridge (created later).

   # ifconfig eth<N> 0.0.0.0 promisc up

   The promiscuous mode allows the physical (or virtual) network interface to accept the entire volume of incoming packets. This mode is essential for consistency of the information transfer.
   
   

3. In case the firewall is enabled on the host system, the following command should be executed to allow the bridge to forward IP packets.

   Red Hat Enterprise Linux 6.x:

   # /sbin/iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT

   This command can also be performed from the bridge configuration script. It has to be executed each time the iptables service is (re)started.

   It is also possible to make this setting system-wide. Either:

   1. Issue the given command from the firewall control panel.

   2. Add the following line to the end of the "/etc/sysconfig/iptables" file:

      -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT

   Red Hat Enterprise Linux 7.x and CentOS 7.x (the '>' is the continuation line character):

   # firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT 1 -m physdev --physdev-is-bridged \ > -j ACCEPT # firewall-cmd --permanent --direct --add-rule ipv6 filter INPUT 1 -m physdev --physdev-is-bridged \ > -j ACCEPT # firewall-cmd --reload

   
   

Virtual interface creation

The creation of the desired number of virtual network interfaces (TAPs) can be performed in the following way:

where “tap<N>” is a name of an instance of the virtual network interface, i.e. “tap0”, “tap1” etc.

Once each virtual network interface instance is created it must be set to promiscuous mode:

Bridge creation

To interconnect the physical and virtual network interfaces created in the previous step, the network bridge must be introduced in the following way:

where “br0” stands for a name of the created bridge.

Now it is possible to add the network interfaces to the created bridge: