[gentoo-user] another "headless device"-question: In search of the LAN

Hi,

For a device (beaglebone black) I am looking for a solution
of the following problem:

This little computer boots a fully blown Gentoo linux. It is 
used mostly as headless device (capturing data from attached 
sensors).

From time to time I want access it via LAN.

If the device was booted without LAN attached, the configured
ethernet was not found and dhcpd fails.
So Gentoo goes into "no LAN"-mode (or something like that).



Is there a less "waiting for the timeout"-prone way to refresh
the status of the LAN beside putting the accoring init-script
into a cron job ???


Is there a way to check, whether a RJ45 was plugged into the 
device and if so to start init-script then?

Thank you very much in advance for any help!
Best regards,
mcc