The Internet
(Back to top)
The Internet has had a relatively brief, but explosive history so far.
It grew out of an experiment begun in the 1960's by the U.S. Department
of Defense. The DoD wanted to create a computer network that would continue
to function in the event of a disaster, such as a nuclear war. If part
of the network were damaged or destroyed, the rest of the system still
had to work. That network was ARPANET, which linked U.S. scientific and
academic researchers. It was the forerunner of today's Internet.
In 1985, the National Science Foundation (NSF) created NSFNET, a series of networks for research and education communication. In 1984 the National Science Foundation got into the act, through its Office of Advanced Scientific Computing. The new NSFNET set a blistering pace for technical advancement, linking newer, faster, shinier supercomputers, through thicker, faster links, upgraded and expanded, again and again, in 1986, 1988, 1990. And other government agencies leapt in: NASA, the National Institutes of Health, the Department of Energy, each of them maintaining a digital satrapy in the Internet confederation.
The nodes in this growing network-of-networks were divvied up into basic varieties. Foreign computers, and a few American ones, chose to be denoted by their geographical locations. The others were grouped by the six basic Internet domains gov, mil, edu, com, org and net. (Graceless abbreviations such as this are a standard feature of the TCP/IP protocols.) Gov, Mil, and Edu denoted governmental, military and educational institutions, which were, of course, the pioneers, since ARPANET had begun as a high-tech research exercise in national security. Com, however, stood for commercial institutions, which were soon bursting into the network like rodeo bulls, surrounded by a dust-cloud of eager nonprofit orgs.(The "net" computers served as gateways between networks.) In todays world the internet can be seen as a huge interconnections of networks around the world, thereby enabling every computer on the internet to communicate with the others.
LAN
(Back to top)
Local Area Network : A data network intended to serve an area
of only a few square kilometers or less. Because the network isn known
to cover only a small area, optimizations can be made in the network signal
protocols that permit data rates up to 100Mb/s
WAN
(Back to top)
Wide Area Network : A network, usually constructed with serial
lines, which covers a large geographic area
Introduction
to Routing and Routers
Routing
(Back to top)
It is the process by which information (in the form of data packets-Datagrams)
is Routing involves two basic activities: determining optimal routing paths
and transporting information groups (typically called packets) through
an internetwork. In the context of the routing process, the latter of these
is referred to as switching. Though switching is relatively straightforward,
path determination can be very complex.
Routers
(Back to top)
These are internetworking devices that connect Local Area Networks
(LAN's) to each other and to Wide Area Networks (WANs). The purpose of
interconnecting LANs and WANs is to enable users on one network to share
information and resources with users on other networks. By using the right
combination of internetworking devices, it is possible to build large,
unified networks that are enterprise-wide, or even global in scope. In
order to traverse a LAN, every packet is encapsulated in a LAN frame. Routers
direct traffic by the network address for each packet. When routers are
used for internetworking, the ends stations communicate indirectly. A router
receives only the packets that are addressed to it by an end station or
another router. End stations communicate with a router, which communicates
in turn with either the destination station or another router. This continues
until the destination station is reached.
IP addresses
(Back to top)
IP addresses are unique addresses given to machines(computers) on a
network. IP addressing is based on the concept of hosts and networks. A
host is essentially anything on the network that is capable of receiving
and transmitting data packets on the network, such as a workstation or
a router. It is not to confused with a server: servers and client
workstations are all IP hosts. The hosts are connected together by one
or more networks. The IP address of any host consists of its network address
plus its own host address on the network. An IP address is 32 bits wide,
it is composed of two parts: The network number, and the Host number [1,
2, 3]. By convention, it is expressed as four decimal numbers separated
by periods, such as "200.1.2.3" representing the decimal value of
each of the four bytes. Valid addresses thus range from 0.0.0.0 to 255.255.255.255,
a total of about 4.3 billion addresses.
IP addressing Scheme
(Back to top)
There are Basically 5 classes of IP addresses(Classes A, B, C, D and
E). The first few bits of the address indicate the Class that the address
belongs to. The bits are labeled in network order, so that the first bit
is bit 0 and the last is bit 31(4 octets), reading from left to right.
Class D addresses are multicast, and Class E are reserved. In the class
A type of network the first octet is reserved for the network number na
the other 3 octets identify the host number. In the class be type of network,
the first 2 octets are reserved for the network number and the other 2
for the host number The range of network numbers and host numbers may then
be derived:
| Class | Range of Net Numbers | Range of Host numbers |
| A | 0 - 126 | 0.0.1 - 255.255.254 |
| B | 128.0 - 191.255 | 0.1 - 255.254 |
| C | 192.0.0 - 254.255.255 | 1 - 254 |
Routing Protocols
(Back to top)
Routing Protocols are protocols that accomplishes routing through the
implementation of a specific routing algorithm. Their main job is to maintain
a sophisticated, updated routing table, which are refered by the router
for ditermination of path while transmiting datagrams over the network.
The Routing Protocols can be divided into 3 broad catagories.
Back View
Router hardware
connections :
(Back to top)
Note : The Installation and Configuration documented here are in many
ways specific to the Cisco 2600 Router.
This section describes how to connect a console terminal and a modem
to the router. You can connect only a terminal to the console port. Use
the auxiliary port with a terminal or a modem, ONLY for remote access to
the router. These ports provide administrative access to your router either
locally (with a console terminal) or remotely (with a modem).
Take the following steps to connect a terminal or a PC running terminal
emulation software to the console port on the router:
Step 1 :- There are two types of
RJ-45 cabling, straight and rolled. If you hold the two ends of an RJ-45
cable side by side, you'll see eight colored strips, or pins, at each end.
If the order of the colored pins is the same at each end, then the cable
is straight. If the order of the colors is reversed at each end, then the
cable is rolled. Use a rollover cable to connect the console port (or auxiliary
ports) to your computer. You can identify a rollover cable by comparing
the two modular ends of the cable. Holding the cables side-by-side, with
the tab at the back, the wire connected to the pin on the outside of the
left plug should be the same color as the wire connected to the pin on
the outside of the right plug.
Identifying the Rollover Cable :
Step 2 :- Connect the Console on the router to the terminal (COM Port) using an RJ-45 rollover cable and an RJ-45-to-DB-25 or RJ-45-to-DB-9 adapter, the provided adapter will be labeled TERMINAL.
Step 3 :- Configure your terminal or terminal emulation software (Ex : Hyper terminal) for 9600 baud, 8 data bits, no parity, and 2 stop bits. Because hardware flow control is not possible on the console port, it is not recommend that modems be connected to the console port. Modems should always be connected to the auxiliary port.
Step 4 :- For routers with AC input, plug the router's power cord into a three-terminal, single-phase power source that provides power within the acceptable range. Power ON the router. The LED labeled SYSTEM on the front panel should go on.
The plug-socket combination
must be accessible at all times because it serves as the main disconnecting
device.
Never operate the router
unless the unit is completely closed to ensure adequate cooling.
For more information on hardware installation lookup cisco home page or clickhere !!!
General
guidelines for Configuring the Cisco 2600 series Route
( Back to top)
The focus of this document is to introduce a new Cisco Internetworking
Operating System (IOS) user to the IOS command line interface (CLI). After
reading this document, a new user will understand how to use the IOS CLI
to configure and manage an IOS router.
CLI Architecture
(Back to top)
A Cisco IOS router command line interface can be accessed through either
a console connection, modem connection, or a telnet session. Regardless
of which connection method is used, access to the IOS command line interface
is generally referred to as an EXEC session.
As a security feature, Cisco IOS separates EXEC sessions into two different access levels - user EXEC level and privileged EXEC level. User EXEC level allows a person to access only a limited amount of basic monitoring commands. Privileged EXEC level allows a person to access all router commands (e.g. configuration and management) and can be password protected to allow only authorized users the ability to configure or maintain the router.
For example, when a session is started, the router will display a "Router>" prompt. The right arrow (>) in the prompt indicates that the router is at the USER exec level. The User exec level does not contain any commands that might control the operation of the router(e.g. reload or configure) . To list the commands available at the USER exec level, type a question mark (?) at the Router> prompt. (This feature is referred to as context sensitive help.).
Word help can be used to obtain a list of commands that begin with a
particular character sequence. To use word help, type in the characters
in question followed immediately by the question mark (?). Do not include
a space before the question mark. The router will then display a list of
commands that start with the characters that were entered.
Example :
Router# co?
configure connect copy
Command syntax help can be used to obtain a list of command, keyword, or argument options that are available based on the syntax the user has already entered. To use command syntax help, enter a question mark (?) in the place of a keyword or argument. Include a space before the question mark. The router will then display a list of available command options with <cr> standing for carriage return. The following is an example of command syntax help:
Router# configure ?
memory Configure from NV memory
network Configure from a TFTP network host
overwrite-network Overwrite NV memory from TFTP network host
terminal Configure from the terminal
<cr>
Critical commands (e.g. configuration and management) require that the user be at the privileged EXEC level. To change to the privileged EXEC level, type "enable" at the Router> prompt. If an enable password is configured, the router will then prompt for that password. When the correct enable password is entered, the router prompt will change to "Router#" indicating that the user is now at the privileged EXEC level. To switch back to USER exec level, type "disable" at the Router# prompt. Typing a question mark (?) at the privileged EXEC level will now reveal many more command options than those available at the USER exec level. The text below illustrates the process of changing execution levels.
Router> enable
Password: [enable password]
Router# disable
Router>
Note: The router will not echo the password that is entered.
Once an EXEC session is established, commands within Cisco IOS are hierarchically structured. In order to successfully configure the router, it is important to understand this hierarchy. To illustrate this hierarchy, the following Figure provides a simple high-level schematic diagram of some IOS commands.
Command Hierarchy
(Back to top)
OSI CLI Hierarchy