/sbin/ifdown does not source /etc/sysconfig/network.

Traditionally this isn't really necessary for devices for which you just ifconfig it down,
but IPv6 can use a little more sophisticated approach.  However, this will not be done
for 'eth' devices because:

if [ "${NETWORKING_IPV6}" = "yes" ]; then
    /etc/sysconfig/network-scripts/ifdown-ipv6 $DEVICE
fi

and NETWORKING_IPV6 is not known in this context.


I suggest that /etc/sysconfig/network be sourced either 
 1) beginning of the file (this might _perhaps_ break some really
controversial OTHERSCRIPT's if they use GATEWAY 
 2) after OTHERSCRIPT is exec'ed