How do I get my NIC going again using ifconfig?

[liquid]

Hi everyone,

Last night I was helping a guy out trying to install FreeBSD for the
first time.  His cable connection is DHCP and I have very little
knowledge of how to set that up since it's been so long since I've had
to do so.  The result is I went to /stand/sysinstall and "pretended" to
setup my interface through there so I'd be able to see what he was
seeing.  I chose no to IPV6, yes to DHCP.. As it's searching for a dhcp
server, I wind up getting disconnected because my interface that has the
public IP suddenly loses that IP.  Somehow, from this point forward the
inet6 IP (which is bogus, I have ipv6 installed for ipv6-ipv4 tunneling
only) takes precedence.  As such, despite all my efforts, and 3-4
re-reads of the ifconfig and route man pages, I was unable to get online
without rebooting.

Is there any other way around this in case this happens another time?  I
recall that many months ago I was tinkering with ifconfig and the same
scenario reproduced itself. I had to reboot in order to get back online.
Also, inconfig rl0 destroy doesn't appear to work.  When I'd try to
remove the inet6 address it would give me an error, something about
PROTO.localhost-v6.rev.  Sorry I can't remember more - by this time it
was already 4 AM, and it didn't appear to log anywhere unfortunately.

If anyone has any tips on how to avoid this for next time it would be
greatly appreciated.

TIA,
Sandro