Block dropbox by firewall (mikrotik)

Visit this site to check the ip address which use dropbox.

Dorpbox use these ipaddress: 
162.125.0.0/16
64.124.102.192/30
199.47.216.0/22
108.160.160.0/20
205.189.0.0/24
209.99.70.0/24
45.58.64.0/20

208.185.144.160/27


Before adding those IPs, backup your router configuration files.
Run this on mikrotik terminal:

/ip firewall address-list 

add address=162.125.0.0/16 list=Dropbox

add address=64.124.102.192/30 list=Dropbox

add address=199.47.216.0/22 list=Dropbox

add address=108.160.160.0/20 list=Dropbox

add address=205.189.0.0/24 list=Dropbox

add address=209.99.70.0/24 list=Dropbox

add address=45.58.64.0/20 list=Dropbox

add address=208.185.144.160/27 list=Dropbox

/ip firewall filter
add action=drop chain=forward dst-address-list=Dropbox

Resource: 

How to block IP-range

Subnet Mask Cheat Sheet