/etc/sysconfig/network 
-----------------------
NETWORKING=yes
HOSTNAME=jade.biology.duke.edu

/etc/sysconfig/network-scripts/ifcfg-eth1
-----------------------------------------
DEVICE=eth0
BOOTPROTO=static
ONBOOT=no
IPADDR=10.0.0.3
NETMASK=255.255.255.0


When I do a ifup eth1, I get 
ipcalc: netmask expected
yet it brings the interface up just fine. Same config files under 6.2/7.0 produced no error/warning.

echo's put in the ifup script show that the ipcalc that is doing this 
is the one here:
    if [ "${GATEWAYDEV}" = "" -o "${GATEWAYDEV}" = "${DEVICE}" ]; then
        # set up default gateway
        echo GATEWAY
        if [ "${GATEWAY}" != "" -a "`ipcalc --network ${GATEWAY} ${NETMASK}`" = "NETWORK=${NETWORK}" ]; then
            route add default gw ${GATEWAY} ${DEVICE}
            DEFGW=${GATEWAY}
        elif [ "${GATEWAYDEV}" = "${DEVICE}" ]; then
            route add default ${DEVICE}
        fi
        echo end GATEWAY
    fi

but as that ipcalc call is the same as one before. Some goofy echo's 
in there show that the NETMASK variable is getting set, but I don't know why ipcalc isn't "seeing" it.

(For reference, this laptop doesn't have 2 ethernet interfaces - I use
eth1 as an alternate config file for a different network.)

If you need more info, please email.