Odd Problems setting up RS6000 on TCP/IP network

[Russell A. Heise]

 roode at anansi.acs.uci.edu (Dana Roode) writes:

 > ...
 >
 > One of our faculty has now taken delivery of the first purchased RS6000 on
 > campus - it occurs to me now I dont know what O/S version he has,
 > but it's whatever IBM is shipping.  I went over to get the network
 > setup using SMIT.  I used the "minimal (basic?) setup" option under the
 > communications menu (my memory is a little fuzzy) and ran through
 > the menu that sets hostname, netmask, static routes, etc..  Everything was
 > obvious except for the name of the interface.  IBM calls "en0"
 > "standard ethernet" and "et0" "IEEE 802.3 ethernet" - Im not sure
 > what I want as I thought 802.3 was "Standard".  To add to my confusion,
 > whenever I make a change to either interface it says "inet0" changed,
 > and the /dev/xxx file has still a different name.
 >
 > What is the correct interface to use?

 To understand the IBM naming scheme, you have to know a little history
 of the Ethernet (trademark Xerox Corp.) development.  When Xerox and its
 associates originally published the Ethernet standard, it was known
 simply as Ethernet.  Later, Xerox made some modification/improvements
 in the protocol and published a new standard, called Ethernet II.  This
 protocol has become the de facto industry-standard Ethernet protocol and
 is supported under AIX 3 as "standard ethernet" or en0.

 Later still, the IEEE decided to develop some manufacturer-independent
 standards for networking.  One of these standards, IEEE 802.3, defines a
 CSMA/CD baseband bus network very similar to Ethernet II.  AIX 3
 supports this standard as "IEEE 802.3 ethernet" or "et0".

 In fact, machines using IEEE 802.3 can communicate with each other on
 the same bus as machines using the Ethernet II.  However, the two sets
 of machines cannot directly intercommunicate.  To do that, you need one
 machine that can talk both protocols to act as a gateway.
 >
 > I ended up deleting en0 after it would not work (using SMIT), and
 > started over using et0.  Still didnt work.  I noticed that all my
 > routes (as per netstat -n -r) where going through the loopback
 > interface lo0 and that "ifconfig lo0" reported the loopback address
 > was set not to 127.0.0.1 but to the host ip address.  No wonder things
 > were not working, all routing was through the loopback, or so it seems.
 >
 > I manually reset lo0 and got the network working to a single system
 > on the connected subnet, but it refused to work to any other system
 > on that subnet.
 >
 > How can I start over and do the configuration right?  Can someone
 > explain how this all works?  (I have managed Unix system for years
 > and on most others getting the initial ifconfig correct in rc.whatever
 > as well as a route command or two is all that is ever needed to make
 > the system work).

 I recommend the following steps:

   - Reboot the RISC System/6000
   - Use SMIT and remove all those unusual routes
   - Use SMIT to remove any and all traces of both en0 and et0
   - Talk to the administrators of the other machines on your network and
     determine which network protocol those machines support
   - Reboot the RS/6000 to start anew
   - Use SMIT to add the interface used by the other machines
   - Use SMIT to add whetever routes you need

 Always use SMIT to make these changes.  SMIT automatically updates the
 ODM (Object Database Manager) data base when you make changes.  AIX uses
 the ODM data base to configure the system each time it starts.  If you
 manually make changes without updating the data base, the changes will
 be lost when you re-boot.

Russ Heise, AIX Technical Support, IBM