[linux-tr] Routing between two TR with Madge cards

[P.Gillingwater@iaea.org]

Hi there,

I have RH Linux 5.2, with two Madge PCI TR cards, which I want to use to
route between two Token Rings.

Getting the two cards working was quite straightforward, with a little magic
in the /etc/conf.modules, and with the Alpha test Madge drivers.

Things seemed to work fine, with PING working just great between both nets,
in both directions.  Running SMB through the router was problematic,
however, with unusual problems -- sometimes a directory would appear, but
then hang.

Some simple analysis showed that PING packets with a size of more than 1995
bytes were being dropped by the Linux kernel (we assume.)

The MTU size was set to 2000, so I tried increasing MTU with the ifconfig
command, but no dice.  Madge support suggest the following:

"Under Linux kernels 2.0.x there is a kernel imposed maximum frame size of
TRN of 2000 bytes. This includes the CRC. So 1995 sounds about right."

This sounds like a problem to me.  I guess PING is not fragmented, but
expect that SMB should be -- so can anyone suggest how to resolve this?
Perhaps I could reduce the MTU size.  What do others see?

I also tried a PING sweep from a Cisco router to another RH Linux box,
running the IBM TR driver, with similar results, i.e., failure just under
2000 byte size.  So to me it doesn't sound like a driver problem, but
something more fundamental in the kernel.

Any assistance would be much appreciated.

Thanks,

Paul Gillingwater <P.Gillingwater@iaea.org>
Internet Systems Administrator
International Atomic Energy Agency [http://www.iaea.org]