ZyXEL Communications P-870H Series User Manual page 23

Chapter 1 Introducing the ZyXEL Device
You can also configure IP filtering on the ZyXEL Device for secure Internet access.
When the IP filter is on, all incoming traffic from the Internet to your network is
blocked by default unless it is initiated from your network. This means that probes
from the outside to your network are not allowed, but you can safely browse the
Internet and download files.
23
P-870H/HW Series User's Guide