db@desktop:/home/db/work/rrdtool> cat update-bandwidth.sh 
#!/bin/sh
RRDFile=/home/db/work/rrdtool/bandwidth.rrd

while [ 1 ]
do
        data=`/usr/bin/netstat -ib | /usr/bin/grep nve0 | /usr/bin/grep Link | /usr/bin/awk '{ print $7":"$10; }'`
        /usr/local/bin/rrdtool update $RRDFile "N:$data"
        sleep 5
done