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AN-018

April 2001

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Document:	Ethernet adapters in CHARON-VAX
Order Number:	AN-018
Revision:	0
Pages:	1
Original Filename:	AN-018.pdf

OCR Text

CHARON-VAX application note
AN-018 Ethernet adapters in CHARON-VAX
Author:

Software Resources International

Date: 31 April 2001

In CHARON-VAX, the user is able to set two different addresses for the emulated network card
(typically a DEQNA or DELQA). One of them stands for the permanent Ethernet address of the
emulated Ethernet controller. The other one is calculated by the CHARON-VAX utility NetSetup and
is applied to the physical Ethernet controller that provides the interface between the emulated Ethernet
controller and the physical Ethernet media. This is the active Ethernet address.
Some software uses the permanent Ethernet address of the Ethernet controller as a software
protection key. If the correct address is to be emulated by CHARON-VAX, it is necessary to enter the
required address as a substitute for the permanent Ethernet address of emulated Ethernet controller.
The emulator provides the optional configuration command "station" to change the permanent address.
For example:
load DEQNA WHA
set WHA interface="\Device\Packet_{...}"
set WHA station="08-00-2b-36-54-26"

Some software requires a particular address to be used as the active Ethernet address of emulated
Ethernet controller. This is for instance the case of DECnet, which calculates the Ethernet address
based on desired DECnet address. In this case, NetSetup must be used to apply that particular address
to the physical controller. At start-up, CHARON-VAX will use this address as the active address, but
will also use it by default as the permanent address of emulated Ethernet controller. Only this default
permanent address is overruled by the optional "station" parameter in the configuration file.
This implies that it is impossible to run two different applications that both require specific (different)
active Ethernet addresses, because only one active Ethernet address can be in effect at the time. This is
a limitation of Ethernet, not of CHARON-VAX. Usually the application determining the active
address is DECnet. Consequently, all other applications must work with any active Ethernet address
(products like TCPware obey this rule).
Note that the “station” parameter is different from the “address” parameter. The latter defines the Qbus
address of the emulated Ethernet adapter, with 0x3ff920 as default value. According to the Qbus
standards, CHARON-VAX supports two Ethernet adapters; a second adapter can be configured with a
specified non-default address.
In summary, in CHARON-VAX the active Ethernet address can differ from permanent Ethernet
address. NetSetup and the “address” parameter serve two different purposes: use NetSetup to set the
active Ethernet address (required for DECnet to function) and the optional "station" parameter for
applications requiring a specific permanent Ethernet address.
[30-18-018]

©2001 Software Resources International. This document is provided for information only and is not a legally binding offer.
Software Resources International reserves the right to change the product specifications without prior notice or retire the
product. The CHARON name and its logo are a registered trademark of Software Resources International. For further
information: www.charon-vax.com, Email: vaxinfo@vaxemulator.com