CHARON-VAX for Linux virtual network

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General description

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

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

• Using "ncu" utility
• Manually

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Using "ncu" utility to establish CHARON virtual network

Login a root. Start "ncu" utility:

Enter "B" or "b" 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 a number of the virtual network Interfaces to be created (2 in our example):

Now enter "S" or "s" to see the created virtual interfaces:

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 "E" or "e" to quit "ncu" utility.

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Manual configuration of CHARON virtual network 

Preparation of the host to create the virtual network

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

   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:

   # /sbin/iptable -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

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Virtual interface creation

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:

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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: