Billion Electric Company BiGuard 2 - Manual (Page 138)

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connected to at least two networks. Usually, this is a LAN and a WAN that is
connected to an ISP network. Routers are located at gateways, the places where
two or more networks connect. Routers use headers and forwarding tables to
determine the best path for forwarding the packets, and they use protocols to
communicate with each other and configure the best route between any two hosts.
Routers can vary in performance and scale, the types of physical WAN connection
they support, and the number of routing protocols supported. BiGuard 2/10 offers a
convenient and powerful way for small-to-medium businesses to connect their
networks.
D.2.2 Why use a Router?
While large bandwidth can easily and inexpensively be provided in a LAN, having
high bandwidth 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 efficiently 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.
D.2.3 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 2/10 supports the RIP protocol. RIP also supports subnet and multicast
protocols. RIP is not required for most home applications.
D.3 Firewall Basics
D.3.1 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 functionality of a NAT router, the