The latest ifup doesn't set the default route correctly. Below is a fix

--- ifup.orig   Tue Mar 13 23:19:06 2001
+++ ifup        Tue Mar 13 23:17:49 2001
@@ -166,7 +166,7 @@
 
     if [ -z "${GATEWAYDEV}" -o "${GATEWAYDEV}" = "${DEVICE}" ]; then
        # set up default gateway
-       if [ -n "${GATEWAY}" -a "`ipcalc --network ${GATEWAY} ${NETMASK}`
2>/dev/null" = "NETWORK=${NETWORK}" ]; then
+       if [ -n "${GATEWAY}" -a "`ipcalc --network ${GATEWAY} ${NETMASK}
2>/dev/null`" = "NETWORK=${NETWORK}" ]; then
            route add default gw ${GATEWAY} ${DEVICE}
            DEFGW=${GATEWAY}
        elif [ "${GATEWAYDEV}" = "${DEVICE}" ]; then