CHARON-AXP for Linux virtual network

Table of Contents

General description

It is strongly recommended to use only physical network adapters for CHARON-AXP networking to gain maximum performancesIn 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 "ncu" utility to establish CHARON virtual network

Login as root and start the "ncu" utility:

# ncu

CHARON Network Configuration Utility, STROMASYS (c) 2014-2019 Version 1.6 

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

:> 3


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):

Specify the interface to be used for BRIDGE:eth1
How many tap should be created:2
Forming the bridge: ..1..2..3..4..5.. addif tap0 .. addif tap1 ..7..8 done!

Formed bridge br0_eth1 attached over eth1...

 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

:> 7

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

:> 8

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:

    # 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:

# tunctl [-t tap<N>]

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:

# /sbin/ifconfig tap<N> promisc up


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:

# /usr/sbin/brctl addbr br0

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

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

# /usr/sbin/brctl addif br0 eth<N>
# /usr/sbin/brctl addif br0 tap0

# /usr/sbin/brctl addif br0 tap<N>


Example:

# /usr/sbin/brctl addif br0 eth1

# /usr/sbin/brctl addif br0 tap0


The proposed configuration assumes one and only one network bridge so loops are not possible. It is required to turn off the spanning tree protocol with the following command:

# /usr/sbin/brctl stp br0 off

Starting bridge

To start the created bridge “br0”, use the following command:

# /sbin/ifconfig br0 up

Usage of the virtual interface in CHARON-AXP configuration

Once the “tap<N>” interfaces have been created, the load command maps those interfaces to CHARON-AXP:

...
load tap_port/chnetwrk XQA0 interface="tap<N>"

... 



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