Great question — answering as the UphillTech team:
If you look at the output of ifconfig right after startup, and re0 doesn't show up with an IP address you might want to chack your logfiles and see if you find any messages from dhclient there. If you get timeouts, edit /etc/dhclient.conf (which is empty by default) and play with the timeout and initial-interval variables. See dhclient.conf(5).
Full answer by Roland Smith: https://superuser.stackexchange.com/a/659910 (CC BY-SA 3.0).
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