Ref: 13680004
Title: Connecting Two 3+ Networks With a 3Com Internetwork Bridge
Date: 11/07/89

Copyright 3Com Corporation, 1991.  All rights reserved.

Caution:  Before beginning any procedure below, make sure you have copies of
the original domain files in case of problems.

1.  If it is a new installation, make sure the network numbers on both
networks match.

2.  For an existing network, change one of the network numbers
to match the other network number.

a.  Type 3N DIR DOMAIN <domain name> to find the network number of a
domain.

b.  Type 3N MOD DOMAIN to change the network number of the domain.

c.  Type 3N MOD SERVER to modify server names within that domain.

Be sure to change the network number of all domains that are home on that
network.

d.  Set the server to maintenance mode and reset it.

e.  Put the System Software #1 disk in a workstation and type 3C START to
get the A:\>> prompt.

f.  Change the current drive and directory to C:\3PLUS\3CONFIG.

g.  Run 3INS and follow these steps:

    1.  Select option 2 - Configure Peripherals and Services.
    2.  Select option 3 - Change Name Service Information.
    3.  Change the network number.
    4.  Press CTRL+A to save the change.
    5.  Exit 3INS.

3.  Copy the NS_DOM files from each 3+Name server onto the other server,
renaming them so that there are not duplicate domain names in the same
network.  See the following example for detail:

                 Segment #1                     Segment #2
                Server -  As                  Server - Giant
             NS_DOM.000  =  CSO             NS_DOM.000  =  ESD
             NS_DOM.001  =  HQ              NS_DOM.001  =  MKT
             NS_DOM.002  =  MIS

a.  Copy NS_DOM.000 and .001 files from Segment #2 to NS_DOM.003
and .004 of Segment #1.

b.  Copy NS-DOM.000, .001 and .002 files from Segment #1 to
NS_DOM.002, .003 and .004 of Segment #2.

Now, Segment #1 can send mail to Segment #2, and the users in
Segment #2 can log in from Segment #1 or Segment #2.
For example:

LOGIN Mike Johnson:ESD:3Com from Segment #1.
3F LINK D: \\DWARF:ESD:3Com\APPS

c.  Set the server to Operation mode, and reset it.

d.  Once the Name server is modified and restarted, restart all other
servers on the network, too.  Otherwise, they will be unreachable.

4.  If the service is installed on both segments of the IBs, you will
need to install one or more filters to keep from confusing the service
requestor.

In a logical network, broadcast messages are automatically forwarded by the
bridge to request services.  If more than one node has the service, then
more than one node will answer, confusing the requestor.  Therefore, it
is important to block out duplicate services.  3Com IBs use filters to
do this.

The filters operate on these packet values:  Ethernet address, packet
type, packet size, and protocol-dependent functions.  The following diagram
shows the packet format and associated byte numbering in hexadecimal for
each recognized value.  (The format of the protocol-dependent section is
determined by the protocols used.)

      Dest. Addr.  Source Addr.  Pkt. Type/Lngth   Protocol-dependent

Bytes    0-5          6-B             C-D              (variable)

Byte offset 0 is the first byte of the destination address.
Byte offset 6 is the first byte of the source address.
Byte offset C is the first byte of the packet type or length.
Byte offset E is the first byte that is protocol dependent.

Following are examples of filters to block duplicate services.

For duplicate Name servers:  %1E:%0464,%0:%FFFF,%C:%0600

Socket Number 1E  0464 (Name service)
Destination Address 0  FFFF (broadcast)
Packet Type C  0600 (XNS)

For duplicate Start servers:  %1E:%0401, %0:%FFFF, %C:%0600

Socket Number 1E  0401 (Start service)
Destination Address 0  FFFF (broadcast)
Packet Type C  0600 (XNS)

For duplicate Locators:  %1E:%046D,%0:%FFFF,%C:%0600

Socket Number 1E  046D (Locator packet)
Destination Address 0     FFFF (broadcast)
Packet Type C             0600 (XNS)

For duplicate time servers:  %1E:%0466,%0:%FFFF,%C:%0600

Socket Number 1E  0466 (time service)
Destination Address 0     FFFF (broadcast)
Packet Type C  0600 (XNS)

