You may enter one network of the form 1.2.3.4/5 where '1.2.3.4' is a network address and '5' is the netmask in CIDR notation.
To add multiple addresses, surround the value in brackets ([ and ]) and seperate the values with commas. For example, to specify 192.168.1.0 and 10.10.10.0 as (both 255.255.255.0) as internal networks, enter the following:
[192.168.1.0/24,10.10.10.0/24]