|
2-14
Chapter 2
Planning a TCP/IP Network Infrastructure
Lesson 2: Planning an IP Routing Solution
An IP router is a hardware or software device that connects two local area
networks
(LANs), relaying traffic between them as needed. Part of designing a network
infrastruc-
ture is determining how many LANs you will create and how you will connect
them.
When you are designing a small network, routing is not a major consideration
because
you can put all your computers on a single LAN. For medium-to-large
networks, this is
not a practical solution. You have to create several LANs and then connect
them so that
any computer on the network can communicate with any other computer.
Your IP routing plan can be simple or complex, depending on the size of the
network
installation, the number of LANs you decide to create, and how you choose to
connect the
LANs. A small network might have a single router connecting the LAN to an
ISP to provide
network users with Internet access. A large network installation might
consist of many dif-
ferent LANs, all connected with routers. The ultimate IP routing scenario is
the Internet
itself, which is composed of thousands of networks connected by thousands of
routers.
Typically, an IP routing plan specifies how many LANs there will be in your
network
installation and how you will connect the LANs. The plan should also specify
the types
of routers the network will use, and how the routers will get the
information they need
to forward packets to their destinations.
After this lesson, you will be able to
■ Understand router functions
■ Use routers to connect LANs and wide area networks (WANs)
■ Understand the difference between routing and switching
Estimated lesson time: 20 minutes
Understanding IP Routing
When a computer on a TCP/IP network transmits a packet, the datagram in the
packet
contains the IP address of the destination computer, as well as the address
of the
sender. If the destination address is on the same LAN as the sender, the
packet travels
directly to that destination. If the destination is on a different network,
the sender trans-
mits a packet to a router instead. This router is known as the computer’s
default gate−
way. (In TCP/IP parlance, the term gateway is synonymous with router.) You
specify
the default gateway address for your computers along with their IP addresses
and sub-
net mask during the TCP/IP configuration process.
The default gateway is the interface between the sender’s own network and
all the
other connected networks. When the router receives a packet, it reads the
destination
address and compares the address to the entries in its routing table. A
routing table is
|
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)
.png)