RE: Urgent - AS400 Connectivity Problem -- MIDRANGE-L

Philipp,

At my previous employer we were a large token ring shop running Client
Access (this was 3 1/2 years ago). I changed our NIC address to avoid having
a huge problem if the card should die (and we did have one do that) and the
NIC address being in everything and having to be changed... REALLY saved my
butt with that move :-)

Here we are ethernet and that isn't such a big deal.

Chuck

-----Original Message-----
From: midrange-l-admin@midrange.com
[mailto:midrange-l-admin@midrange.com]On Behalf Of Philipp Rusch
Sent: Friday, April 19, 2002 2:18 PM
To: midrange-l@midrange.com
Subject: Re: Urgent - AS400 Connectivity Problem


Hello Karthik,
changing the MAC address is no pain at all, vary off the ethernet line
go to the LIND/ADPTADR and change it to 420000000001,
420000000002 and so on.
For every machine on your LAN you need an exclusive MAC number.
In Ethernet environments, this has to start with '42' hex and the mac
itself is a 12 digit hex number.
A little background: Normally you don't compose your own MAC
addresses as these are burned in at the factory (think of it as a production
serial number). Every producer of network hardware has been assigned
an own range of allowed numbering space, I think the IEEE is taking care
of this, but I am not sure. So when do you need to overwrite the adapter's
own address with something artificial  ? Quite simple: in the days of SNA
there has been a 1:1 relation between SNA node name and the hardware
(MAC) address of that SNA-host. Often you used to have simple numbers
like yours, so it was easy to replace the machine with another without
changing to whole bunch of network definitions for that node in the net.
That's the only secret about it ...  :-)
In the days of IP there is far more flexibility about hardware related
adresses, because when starting TCP/IP on a particular node in a net it
correlates its own mac address to the IP address you gave it (either static
or by asking a DHCP-server) and that pair is maintained throughout the
whole segment you are in until the next time you take this node down.
So your duplicate MACs confused the team of servers in your LAN
completely, they did not know where to send to packets to and even your
ping was starving ...

HTH and regards from germany, Philipp Rusch

KarthikeyanS@lincsoftware.soft.net schrieb:

> Hi All,
>
> I have a problem with my as400 connectivity to my emulator software.   I'm
> trying to connect a 150 model as/400 server (V4R2) system to a emulator
> software here. The problem starts when i ping my as400.  My PC on the
> network is getting the  reply for some time and after some time it gets a
> request time out message. So, what happens is even if i connect to the
> as400 through a emulator software, it connects in the beginning and gets
> disconnected after some time (may be in 2 or 3 minutes after connecting).
> But, If I connect the as400 to a separate hub(where no other pc's are
> connected) and connect my pc to that hub, there is no request time out
> message and I'm able to work in the emulator software without getting
> disconnected.  I think with this i can come to a conclusion that my
as400's
> ethernet card is working fine.   This as400 is connected to a LAN port.  I
> have also tried connecting the as400 directly to the hub or switch, but
> face the same problem.  There are other as400 systems in the network (170
> models V4R4) which are working fine.
>
> What could be the exact problem and where could it be?? Please help me to
> solve this never ending problem ASAP.
>
> Rgds,
> Karthik
>
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