On Thu, 25 Nov 2004 19:46:51 -0500, Max Khitrov <mkhitrov at umd dot edu> wrote:
> 
> When I execute this command: ifconfig em0 media 100BaseTX mediaopt
> full-duplex
> With em0 being my lan interface, I loose any and all connections to the
> firewall. 

it's 100baseTX, not 100BaseTX.  Other than that, that looks fine,
matches what 'man em' says it should be.  If you want to leave it this
way long term, see this page on adding the media and mediaopt options
to your config.xml file. 
http://m0n0.ch/wall/docbook/faq-hiddenopts.html

> This is a built-in nic on a Dell GX260 which is supposed to be
> gigabit (though I'm running it at 100Mbps) and should most definitely
> support full-duplex.

Do you really *need* to force its speed and duplex?  If you don't have
a good reason to do so, you should let it autonegotiate.  There are
always some quirky situations where you need it, but if it's working
fine as is, I'd leave well enough alone.

-Chris