Hello,
because if there is /24, the gentoo-vserver-init-script (to be correct: route is complaining) is complaining about an unknown device or something like that.
man route:
route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0
adds a route to the network 192.56.76.x via "eth0". The Class C netmask modi-
fier is not really necessary here because 192.* is a Class C IP address. The
word "dev" can be omitted here.
Don't know for sure, if it is really needed, but if it's missing, it's not working
HTH,
Steffen