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The emulated Ethernet interfaces of Charon-PAR can be linked either to a

• physical host interface,
• a TAP interface connected to a virtual bridge on the host, or
• (since Charon-PAR 3.0.9) a MACVTAP interface linked to a physical NIC on the host.

Notes for physical interfaces:

• If used directly as a guest interface, offloading parameters must be turned off using the initialization command parameter in the configuration file.
• In cloud environments, the necessary interface settings are not always reflected correctly on the cloud-provided NICs. For such installation settings a MACVTAP interface can be used to provide a dedicated connection without connecting the emulator directly to the physical interface.

Notes for TAP interfaces:

• A TAP interface can either be created by the user or will be created automatically by the emulator if it does not already exist.
• For automatically created TAP interfaces, the user can specify a name or let the emulator select a name.
• A automatically created TAP interface is not automatically added to a bridge, this must be configured via the initialize_command (see the Ethernet Configuration Parameter table below).
• An automatically created TAP interface is deleted automatically upon emulator stop.
• If used in a cloud environment, only internal virtual bridges (no connection to the cloud LAN) are supported.

Notes for MACVTAP interfaces:

• Introduces a transparent bridge interface associated with on physical NIC on the host, and provides a dedicated interface to the emulator.
• Provides an abstraction layer between physical NIC and emulator.
• Physical interface requires no changes in the offloading configuration.
• Fragmentation is performed by Linux on the MACVTAP interface. Jumbo frames on the physical interface will not cause problems.
• Uses same MAC address as the physical interface.
• Suited for associating a dedicated host Ethernet interface to the emulator in cloud environments.

Notes for network configurations on VMware:

• ESXi has configuration parameters that improve security but may block certain emulator NIC configurations.
• One configuration option allows or blocks promiscuous mode (the default mode of operation for Charon-PAR guest NICs).
• Other configuration options allow or block the change of a MAC address or the use of a different, additional MAC address on the same NIC (MAC address changes, Forged transmits).

By default, emulated models have one Ethernet device. Depending on the model, more Ethernet devices can be added.

A guest HP-UX system will perceive the network card as a 10/100 Mbit/s controller running at 10 Mbit/s half-duplex. If the user tries to change this setting using SAM or the lanadmin command, the command will be accepted but the displayed interface settings will not change.  However, the throughput of the emulated network card depends on the combination of network performance, physical network card characteristics, host system and guest system performance - it is not tied to the displayed interface settings. So the actual throughput will be what can be achieved depending on the conditions listed above.

The emulated network devices

• DE 500 PCI based cards (for 64-bit systems), and

• LASI-82596 cards (for the 32-bit system)

do not support Jumbo frames. For physical interfaces, this feature must be disabled in the emulator configuration (together with any other offloading parameters) using the initialize_command parameter.