Why Use A Router; Routing Information Protocol (Rip); Firewall Basics; What Is A Firewall - Billion BiGuard S10 Administration Manual

Why use a Router?

While large bandwidth can easily and inexpensively be provided in a LAN, having high band-
width between a LAN and the Internet can be prohibitively expensive. Because of this, Internet
access is usually done through a slower WAN link, such as a cable or DSL modem. To effi-
ciently use this slower connection, a router acts as a mechanism for selecting and transmitting
data meant for the Internet. By using a router, organizations can enjoy relatively inexpensive
Internet access, while maintaining a high-speed local area network.

Routing Information Protocol (RIP)

Routing Information Protocol (RIP) is an interior gateway protocol that specifies how routers
exchange routing table information. Routers periodically update each other with RIP, changing
their routing tables when necessary.
BiGuard S10 supports the RIP protocol. RIP also supports subnet and multicast protocols. RIP
is not required for most home applications.

Firewall Basics

What is a Firewall?

Firewalls prevent unauthorized Internet users from accessing private networks connected to the
Internet. All messages entering or leaving the intranet pass through the firewall, which examines
each message and blocks those that do not meet the specified security criteria. With the func-
tionality of a NAT router, the firewall adds features that deal with outside Internet intrusion and
attacks. When an attack or intrusion is detected, the firewall can be configured to log the intru-
sion attempt, and can also notify the administrator of the incident. With this information, the
administrator can work with the ISP to take action against the hacker. Against some types of
attacks, the firewall can discard intruder packets, thereby fending off the hacker from the private
network.

Stateful Packet Inspection

BiGuard S10 uses Stateful Packet Inspection (SPI) to protect your network from intrusions and
attacks. Unlike less sophisticated Internet sharing routers, SPI ensures secure firewall filtering
by intercepting incoming packets at the network layer, and analyzing them for state-related
information that is associated with all network connections. User-level applications such as Web
browsers and FTP can make complex network traffic patterns, which BiGuard S10 analyzes by
looking at groups of connection states.
All state information is stored in a central cache. Traffic passing through the firewall is analyzed
against these states, and then is either allowed to pass through or rejected.

Denial of Service (DoS) Attack

A hacker may be able to prevent your network from operating or communicating by launching a
Denial of Service (DoS) attack. The method used for such an attack can be as simple as merely
flooding your site with more requests than it can handle. A more sophisticated attack may
attempt to exploit some weakness in the operating system used by your router or gateway.
Some operating systems can be disrupted by simply sending a packet with incorrect length
information.