Along these lines, we had some very interesting problems when we started migrating from FDDI to Fast Ethernet. Our filers were on FDDI, connected to a FDDI card in a Cabletron SS9000, which had a FDDI-Ethernet bridge. There were a number of SGI and HPs on the Ethernet backbone that had NFS mouting problems with the filers. The Suns and PCs were OK. We finally forced the MTU on the filers' FDDI interface to 1500, and the problem went away.

That sure sounds like the Cabletron packet fragmentation problem you described. We've just finished replacing our older FDDI hubs (CTRN MMAC8s) with Fast Ethernet switches (CTRN SS6000), and changing the filers from FDDI to 100BaseT. Everything is now on one switched Ethernet network, and seems OK (knock, knock).

-warren

-----Original Message----- From: mds@gbnet.net [mailto:mds@gbnet.net] Sent: Friday, December 17, 1999 1:22 PM To: Walsh, Warren (MN65); toasters Subject: RE: toasters and auto negotiation

On Fri 17 Dec, 1999, "Walsh, Warren (MN65)" Walsh_Warren@htc.honeywell.com wrote:

We recently converted our 330 and 540 from FDDI to 100BaseT. We found

that

we had to manually force both the 100BaseT card in the toaster and the specific port on our Cabletron Smart Switch 9000 to 100BaseT-FD. For the 100BaseT card, it was simply changing the auto to 100tx-fd:

ifconfig e5 `hostname`-e5 mediatype 100tx-fd netmask 255.255.248.0

Funny how that auto-negotiation thing never really works, and how much it really affects performance.

Funny, I was only talking with a friend today about how autonegotiation between Sun's and Ciscos works fine, and how Cabletron kit has such irritatingly non-functional autonegotiation in contrast.

In my last job, running any number of Su's, SGI's and NetApp's using Cabletron switches the network guys and I always went hunting for the ports where the collisions were high and the autonegotiation had been left on, or turned back on.. As policy we decided to pin both ends to 100BaseTX-fd no-autonegotiation, because anything else was markedly less effective.

This wasn't the only problem we had with Cabletron kit though - there were some horrors with the spanning tree reconfigurations, and pakcet fragmentation, and adjacent switches somehow bollixing sets of ports on other switches.

Put me right off Cabletron as a networking equipment vendor I have to say. YMMV.

I always quite liked FDDI: most of our filers were on FDDI and, perhaps because of the extra smarts in the cards, the performance was always pretty darned good.

We even got our biggest machines their own Gigaswitch ports - though I never figured out if the cards (DEC cards in NetApp, DEC gigaswitch) went into the full-duplex mode that the DEC network engineers though they might be able to do when plugged straight into the Gigaswitch.

Sure made cabling in the machine room easier using FDDI too. Until they put decent amounts of structured wiring in.

-warren

Warren Walsh Honeywell Technology Center -- End of excerpt from "Walsh, Warren (MN65)"