User manual

Introduction

VAX MP uses host network cards by putting them in promiscuous mode and capturing all the traffic on

the wire, regardless of MAC destination address in the Ethernet packet. If there is a heavy traffic on the

wire, processing all the packets (including packets not actually destined to this host or VAX MP instance

running on it) can cause overhead. In this case it is recommended to connect VAX MP host to the

network via a switch that filters out irrelevant traffic.

For instructions regarding host networking software configuration refer to system-specific sub-section

below for particular host operating system. Note that in most cases you would want to configure

network setup after performing basic OpenVMS installation first. However you want to consult system-

specific section on network configuration before doing VAX MP installation to make sure you host

system has

pcap(libpcap) installed.

Installation of

pcap is optional for execution of VAX MP, but is required for networking with VAX MP, i.e.

in order to be able to run TCP/IP Services for OpenVMS, VAXcluster (VMScluster), LAT or DECnet over

Ethernet for connecting either to other physical or virtual machines over the physical network or via

virtual Ethernet to the host machine itself or to other instances of virtual machines running on the host.

Operation of system-specific network stack differs across various host operating systems, with

significant implications for VAX MP networking configuration set-up.

Windows network stack implements full interchange of packets between host side and virtual side. This

normally allows VAX MP user to set up very simple single-interface networking configuration with just

one interface (one DELQA or DEQNA controller bound to host NIC

) used for communication between

VAX and remote nodes and also between VAX and host node itself and also between VAX and other

virtual machines running on the host. Under Windows, just one single interface normally suffices for all

categories of communications. However even under Windows this is not always the case and more

complex set up may be required in some cases: see notes further down in this chapter on TOE (TCP

offload engine) adapters and Gigabit Ethernet jumbo frames.

Under Linux and OS X,

pcap bound to host NIC allows VAX MP to communicate only with remote nodes,

but not with the host computer itself. The reason is that while

pcap does capture Ethernet packets

arriving to the NIC from external nodes and forwards them to both VAX MP and the host machine, but it

does not fully interchange NIC packets between the host machine and VAX MP.

Packets sent by the host machine generally are visible by the virtual side. However packets sent by the

virtual side generally are not received by the Linux or OS X host network stack since it is not listening in

promiscuous mode – unlike on Windows where network stack does deliver transmitted packets to the

whole stack when the interface is in promiscuous mode, such as after starting

pcap.

Thus under Linux and OS X pcap bound to host machine’s NIC allows VAX MP to communicate with

other machines on the network but establishes no usable link between the host machine and VAX MP.

NIC stands for Network Interface Card.