Ref: 10710034
Title: Using Multiple Servers with Appletalk
Date:  7/5/88

Copyright 3Com Corporation, 1991.  All rights reserved.

3Com's recommended and standard 3+Mac configuration
requires 2 networks:  1 primary Ethernet and 1 secondary Appletalk.  One
server would be physically on both wires, running NetConnect.  Such a
server is internally called a "3NameGateway".  Now you may place more
than 1 server on the Ethernet and everything will still be ok as long
as one is a 3NameGateway.

When you click the 3+File item from the Chooser, a special packet is
sent on the Appletalk called the NBP 3NameGateway lookup.  This packet
uses an Appletalk protocol, not XNS, and therefore cannot have any
equivalence in XNS terms.

As expected, the "3NameGateway" server would send a response packet to
the Mac, identifying itself.  At this time, the Mac would send a
Clearinghouse lookup broadcast, via the gateway that passes it onto
Ethernet.  A Name server, most likely the same server NetConnect
is running on, would send a response.  From now on, things become
similar to the 3+ PC world.  Note that the AppleTalk clients are always
treated as remote clients.

The catch here is that the Mac station, once keyed onto a
3NameGateway, will continue to send packets to it, regardless of the
ultimate destination.  But, everything still works fine because
3NameGateway knows how to route the packets to the correct places.

.h2;CONFIGURATIONS:
1) You have another Ethernet network that you wanted to add to the
   above standard configuration.  This results in 3 interconnected
   networks, 2 of which are Ethernet and 1 is Appletalk.

   On the same Appletalk segment, you may place another server running
   NetConnect, which connects to this new Ethernet. As long as this new
   "3NameGateway" server uses the same network number that the original
   3NameGateway uses for the Appletalk, everything will be fine.

   When you click 3+File in this configuration, you will be presented
   with 2 choices of domains.  By selecting one, the Mac will key
   onto one of the gateway servers.  You will still be able to
   communicate with any server anywhere because the gateway server
   knows how to route.

2) You don't want to add a third network, you are still using the 3Com
   recommended configuration, but you want to put another server on
   that same Appletalk segment.

   This will not work because the Appletalk network really has no Name
   service. The Name server actually resides on the primary network,
   the Ethernet.  Your new server on the Appletalk will, therefore, not
   boot because it won't find a name server.  (The Mac workstations
   don't have this problem because they use the special NBP lookup.)

3) You are not following 3Com recommended procedures, you don't want a
   mixed network environment.  You simply want one PRIMARY
   Appletalk network with multiple servers.

   In this case, none of the servers would run NetConnect, and one of
   them would run 3+Name. There are two problems with this:

   a) Since there is not a 3NameGateway server, NBP lookup packets
      would fail, and you won't be able to login from a Mac station.

   b) There is a secret method whereby you manually designate that the
      server running 3+Name "act" as a 3NameGateway. "Act" is
      appropriate because this server will only be able to respond to
      NBP lookups, but it still won't be able to route packets
      because it is not running NetConnect.

      As long as Mac stations only use this server for all services,
      things will work.  They won't be able to communicate with the
      others because they always "key" onto the 3NameGateway
      server.
