Netcomm NB6W Benutzerhandbuch

Firewall 

The firewall is a kind of software that interrupts the data between the Internet and your computer. It is the 
TCP/IP equivalent of a security gate at the entrance to your company. All data must pass through it, and the 
firewall (functions as a security guard) will allow only authorized data to be passed into the LAN.

What the firewall can do? It can: 

• 

deny or permit any packet from passing through explicitly

• 

distinguish between various interfaces and match on the following fields: 

• 

source and destination IP address 

• 

port

To keep track of the performance of IP Filter, a logging device is used. The device supports logging of the TCP/UDP 
and IP packet headers and the first 129 bytes of the packet (including headers) whenever a packet is successfully 
passed through or blocked, and whenever a packet matches a rule being setup for suspicious packets. 

An example for firewall setup:

Internet

Router

with Firewall Protection

PC 1

PC 2

This picture shows the most common and easiest way to employ the firewall. Basically, you can install a 
packet-filtering router at the Internet gateway and then configures the filter rule in the router to block or filter 
protocols and addresses. The systems behind the router usually have a direct access to the Internet; however 
some dangerous services such as NIS and NFS are usually blocked.

For the security of your router, setting the firewall is an important issue.