Conference netcad::hub_mgnt

2606.0. "DECbridge90 forgetting addr. with LexLink protocol" by RULLE::KLASSON (Sven-Olof Klasson @GOO) Thu Aug 03 1995 11:59

A customer have a number of DEChub90 hubs with DECbridge90 that connects
the hubs to the ethernet backbone.

This causes problems with IBM Lexmark printers. These printers are connected 
to ethernet and communicate with a PC with OS/2 Interact Printer Utility.
The protocol used is LexLink.

The LexLink protocol operates without any broadcasts or periodic hello 
messages. I belive broadcast is only used when starting up PC the servers.
That means when the printer does not operate there is no ethernet packets
sent at all on the ethernet from the printer.
After some time the DECbridge90 forgets about the ethernet address of the
printer since no ethernet packets have been seen.
It's possible to set "Address entry age" to a maximum of 18 hours. But there
is still problems on mondays when there has been no ethernet packets sent
during the weekend.

To recover from this the PC server must be restarted, or the printer has to
be powered off/on.

The current fix for this is to enable flood mode in DECbridge90.
The customer don't like to have flood mode enabled in his DECbridge90 since
he says this causes unwanted packets to be forwarded from the backbone to the
hub. Han want to have the bridging to reduce traffic in the hub backplane
(all hubs have less then 200 stations connected)

I would like to have comments on this problem with Lexmark printers and 
DECbridge90.

Is there any rules/recommendations to use periodic hello messages or
broadcast in ethernet protocols to avoid this problems?

Can we blame the LexLink protocol for this problem?

Any suggestion to solve this in a better way? 
The customer is considering to replace his DEChub90 and DECbridge90 with
other (non-Digital) hubs/bridges.

Rev's on DECbridge90: HW V2.0, ROM V2.0, SW V3.0

Thanks,
Sven-Olof Klasson, CSC Sweden