setting nic to auto (detect speed)

[Mike Kenny]

Using Ubuntu 5.10

I am using a 100Mb NIC and my local network is not great. The network
guys have had a look and say that they have set the switch to auto and
that if I change my NIC from 100Mb to auto I should see considerable
improvements. The man page and help for ifconfig indicate that
changing this setting is supported. But no matter waht sequence of
options and paramters I provide on the command line it seems to
interpreting the text media and/or auto as hostnames, with the
expected results.

Can anybody tell me how to change this setting?

TIA

mike