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Hardware Manual for the Model CG814WG Wireless Cable Modem Gateway
D-10 Networks, Routing, and Firewall Basics
IP Configuration by DHCP
When an IP-based local area network is installed, each PC must be configured with an IP address.
If the PCs need to access the Internet, they should also be configured with a gateway address and
one or more DNS server addresses. As an alternative to manual configuration, there is a method by
which each PC on the network can automatically obtain this configuration information. A device
on the network may act as a Dynamic Host Configuration Protocol (DHCP) server. The DHCP
server stores a list or pool of IP addresses, along with other information (such as gateway and DNS
addresses) that it may assign to the other devices on the network. The CG814WG Gateway has the
capacity to act as a DHCP server.
The CG814WG Gateway also functions as a DHCP client when connecting to the ISP. The
gateway can automatically obtain an IP address, subnet mask, DNS server addresses, and a
gateway address if the ISP provides this information by DHCP.
Internet Security and Firewalls
When your LAN connects to the Internet through a router, an opportunity is created for outsiders
to access or disrupt your network. A NAT router provides some protection because by the very
nature of the Network Address Translation (NAT) process, the network behind the NAT router is
shielded from access by outsiders on the Internet. However, there are methods by which a
determined hacker can possibly obtain information about your network or at the least can disrupt
your Internet access. A greater degree of protection is provided by a firewall router.
What is a Firewall?
A firewall is a device that protects one network from another, while allowing communication
between the two. A firewall incorporates the functions of the NAT router, while adding features for
dealing with a hacker intrusion or attack. Several known types of intrusion or attack can be
recognized when they occur. When an incident is detected, the firewall can log details of the
attempt, and can optionally send email to an administrator notifying them of the incident. Using
information from the log, the administrator can take action with the ISP of the hacker. In some
types of intrusions, the firewall can fend off the hacker by discarding all further packets from the
hacker’s IP address for a period of time.