need to take backup for F5 ltm

There is an iApp for this. Have a look on this thread: https://devcentral.f5.com/articles/f5-automated-backups-the-right-way

I have used the enhanced version of it by inxgeek and it works fine for my customer. That is mentioned in the comments and is downloadable from here: http://download.domingo.dk/data/public/backup-iapp.php.