fddi and ethernet problems

From: Paul Schoenly <pschoen_at_janus.gsfc.nasa.gov>
Date: Tue, 03 Nov 1998 11:03:35 -0500

Hi all-

Our group recently moved buildings. In the old building we had a
100mbps half duplex shared ethernet connection and a fddi connection
(for transferring data to and from other fddi hosts here on base). The
new building has a 100mbps switched ethernet network (half or full
duplex) and the same kind of fddi network.

We have the following interfaces on two AlphaServer 4100's running Digital
Unix 4.0D:
DEC TULIP (10/100) Ethernet Interface
DEC DEFPA (PDQ) FDDI Interface

The ethernet port is the default. We have tried both half and full
duplex.

The problem is that we can see great bandwidth most of the time, but
we have periodic freezes lasting from seconds to minutes. This is most
evident on all our x terminals (we have around 20 10mbps NCD x
terminals).

We've put packet sniffers on everything and our networking crew said
that packets are getting incorrectly routed to the ethernet port even
when the network traffic is coming from a remote FDDI host. They
implied that this was a bug in Digital's FDDI driver.

The problem is that I can use tcpdump to see packets arriving to and
originating from our FDDI port. Also, running a traceroute to their
ethernet and FDDI routers result in output like:

1 ms * 1 ms

This happens every time, with the second packet always being dropped.
I've run this as a cronjob for 3+ days with no variation in the
results.

Has anyone else had any experience in a situation like this? I'm
skeptical that it is our servers' fault since we have not changed any
hardware, firmware, etc. since the move. The only thing that has
changed is the network that we are on.

Thanks in advance!

-- 
Paul Schoenly // System Administrator // GSC  NASA/GSFC
phone: 3016145931 // email: pschoen_at_janus.gsfc.nasa.gov
Received on Tue Nov 03 1998 - 16:07:07 NZDT

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