The version of rc-scripts used by the baselayout ebuilds 1.7.3-r2 and above (rc-scripts-1.2.9) contain a broken /etc/init.d/net.eth0 script. Additional double qoutes have been added throughout the script which break it. For example the eval echo expressions do not evaluate correctly when the double quotes are present. Reverting to the version of net.eth0 in rc-scripts-1.2.8 fixes the problem totally as the quotes are not there.
Is already fixed on CVS. Please search gentoo-user or gentoo-devel for an updated script.
Fixed on CVS. Should be in 1.7.4.