CISCO ROUTER CONFIGURATION
Eng.Ola Abd El-Latif
1st June 2010
INTRODUCTION TO WAN
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A WAN is a data communications network that
spans a large geographic area such as a state,
province, or country
They connect devices that are separated by wide
geographical areas.
They use serial connections of various types to
access bandwidth over large geographic areas.
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A WAN operates at the physical layer and the
data link layer of the OSI reference model.
It interconnects LANs that are usually
separated by large geographic areas.
WANs provide for the exchange of data packets
and frames between routers and switches and the
LANs they support.
WAN DEVICES
ROUTERS
INTRODUCTION TO ROUTERS
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Routers offer many services, including
internetworking and WAN interface ports.
It has a CPU, memory, a system bus, and various
input/output interfaces.
routers connect and allow communication
between two networks and determine the best
path for data to travel through the connected
networks.
routers need the Internetwork Operating System
(IOS) software to run configuration files.
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These configuration files contain the instructions
and parameters that control the flow of traffic in
and out of the routers.
Routers use routing protocols to determine the
best path for packets.
The configuration file specifies all the
information for the correct setup and use of the
selected, or enabled, routing and routed protocols
on a router.
THE INTERNAL COMPONENTS OF A
CISCO ROUTER
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DRAM (dynamic random access memory)
Used to hold packet buffers, ARP cache, routing
tables.
 Running-config also stored in RAM, and most routers
expand the IOS from flash into RAM upon boot.
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ROM (read-only memory)
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Used to start and maintain the router. Holds the
POST and the bootstrap program, as well as the
mini-IOS.
Flash memory (EEPROM : electronically erasable
programmable read-only memory )
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Stores the Cisco IOS , Not erased when the router is
reloaded
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NVRAM (nonvolatile RAM)
Holds router (& switch) configurations
 Not erased when the router is reloaded
 Does not store an IOS.
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Bootstrap
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Stored in the microcode of the ROM, the bootstrap is
used to bring a router up during initialization. It will
boot the router and then load the IOS.
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POST (power-on self-test)
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Stored in the microcode of the ROM, the POST is
used to check the basic functionality of the router
hardware and determines which interfaces are
present.
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Console port (used for configuring router)
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Interfaces (or ports) – LAN/WAN connections
THE ROUTER BOOT SEQUENCE
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Step 1:
The router performs a POST.
 The POST tests the hardware to verify that all
components of the device are operational and
present. For example, the POST checks for the
different interfaces on the router.
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Step 2:
If it passes, The bootstrap then looks for and
loads the Cisco IOS software.
By default, the IOS software is loaded from flash
memory in all Cisco routers.)
The default order of an IOS loading from a router
is Flash, TFTP server, then ROM.
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Step 3:
The IOS software looks for a valid configuration
file stored in NVRAM.
This file is called startup-config and is only there
if an administrator copies the running-config file
into NVRAM.
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Step 4:
If a startup-config file is in NVRAM, the router
will copy this file and place it in DRAM and call
the file running-config.
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The router will use this file to run the router.
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The router should now be operational.
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Step 5:
If a startup-config file is not in NVRAM, the
router will broadcast out any interface that
detects carrier detect (CD) for a TFTP host
looking for a configuration,
and when that fails, it will start the setup mode
configuration process
THE CISCO (IOS)
THE CISCO INTERNETWORK OPERATING
SYSTEM (IOS):
Cisco IOS is the kernel of Cisco routers and most
switches.
 These are some important things that the Cisco
router IOS software is responsible for:
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Carrying network protocols and functions
Connecting high-speed traffic between devices
Adding security to control access and stop unauthorized
network use
Providing scalability for ease of network growth and
redundancy
Supplying network reliability for connecting to network
resources
CONNECTING TO A CISCO ROUTER
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You can connect to a Cisco router to
 configure it.
 verify its configuration.
 check statistics.
You can access the Cisco IOS through
 the console port of a router,
 from a modem into the auxiliary (or Aux) port,
 or even through Telnet.
MANAGEMENT PORT CONNECTIONS
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This page will introduce the console and auxiliary
(AUX) ports, which are also known as the
management ports.
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These asynchronous serial ports are not designed as
networking ports.
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The console port is required for the configuration of
the router.
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Not all routers have an auxiliary port.
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When the router is first put into service, there are no
networking parameters configured.
DIRECT CONFIG.
CONSOLE PORT
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is usually an RJ-45 connection located at the back of the
router.
by default, there’s may or may not be a password set.
The console port is a management port that is used to
provide out-of-band access to a router.
It is used to set up the initial configuration of a router and
to monitor it.
The console port is also used for disaster recovery
procedures
INDIRECT CONFIGURATION
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The router can also be remotely configured
through the configuration port across an
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IP network using Telnet
or by dialing to a modem connected to the
console or auxiliary port on the router.
AUXILIARY PORT
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which is the same thing as a console port.
But an auxiliary port also allows you to configure
modem commands so that a modem can be connected to
the router.
Using Aux port allow you to dial up a remote router
and attach to the auxiliary port if the router is down
and you need to configure it out-of-band (meaning out
of the network).
THE PROGRAM
TELNET.
The third way to connect to a Cisco router is inband, through the program Telnet.
 ( In-band ) means configuring the router through
the network.
 Telnet is a terminal emulation program that acts as
though it’s a dumb terminal.
 You can use Telnet to connect to any active interface
on a router, such as an Ethernet or serial port.
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CONFIGURING A SINGLE CISCO ROUTER
Router Modes
Moving between modes
Configuring a Router Name
Setting the Passwords
Password Encryption
Router Interfaces
Configuring a Fast Ethernet Interface
Configuring a Serial Interface
Configuration Commands
Show commands
NOTE THAT :
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In normal cases the interface will attached to a
CSU/DSU type of device that provides clocking for the
line to the router, you can use the serial interface to
connect to a DCE network via a CSU/DSU that
provides the clocking to the router interface.
But if you have a back-to-back configuration
(serial – serial ), one end— the data communication
equipment (DCE) —must provide clocking and
bandwidth , while the other end DTE (data terminal
equipment) is not set to provide clocking.
COLLISION DOMAIN AND BROADCAST DOMAIN:
The LAN that use hub to connect together, this
network have one broadcast domain and one
collision domain.
 A switch (and bridge) breaking up collision
domains But make the network is still one
broadcast domain
 Routers break up a broadcast domain —the set of
all devices on a network segment that hear all
the broadcasts sent on that segment. Also break
collision domain.
 Remember that Switches separate Collision
domains and Routers separate Broadcast
domains (as well as collision domains)
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EXAMPLE:
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Broadcast Domain #1
(1) Hub1 to Switch1 is part of the same collision
domain as the other connections out of Hub1
(2) Switch1 has a collision domain on its
connection out the top of the device in the
diagram
(3) Switch1 to Router1 is a collision domain
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Broadcast Domain #2
(1) Router1 to Switch2 is a collision domain
(2) Switch2 to Router2 is a collision domain
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Broadcast Domain #3
(1) Router2 to Bridge1 is a collision domain
(2) Bridge1 has a collision domain on its
connection out the right of the device in the
diagram
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Total Broadcast Domains = 3
Total Collision Domains = 7
ETHERNET CABLING :
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Three types of Ethernet cables are available:
Straight-through cable
 Crossover cable
 Rolled cable
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STRAIGHT-THROUGH CABLE
Four wires are used in straight-through cable to
connect Ethernet devices.
 It is relatively simple to create this type.
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CROSSOVER CABLE
The same four wires are used in this cable as in
the straight-through cable;
 we just connect different pins together, as shown
in figure.
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ROLLED CABLE
Although rolled cable isn’t used to connect any
Ethernet connections together,
 You can use a rolled Ethernet cable to connect a
host to a router console serial communication
(com) port.
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How to connect devices???
 NIC, Router, Access point, Networked Printer
Transmit on 1 ,2 and Receive on 3,6
 Hub, Switch Devices Transmit on 3,6 and
Receive on 1,2
 We want to connect transmitter pins with
receiver pins so that and according to above
information, and as an example: to connect
 - Switch to switch == use crossover cable
 - Router to switch or hub == use straight cable
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ROUTING
Routing is taking a packet from one device and
sending it through the network to another device
on a different network.
 The router learns about remote networks from
neighbor routers or from an administrator.
 The router then builds a routing table (a map of
the internetwork) that describes how to find the
remote networks.
 If a network is directly connected, then the router
already knows how to get to it.
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If a network isn’t directly connected to the router,
the router must use one of two ways to learn how
to get to the remote network:
 STATIC ROUTING
 DYNAMIC ROUTING
STATIC ROUTING
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meaning that someone must hand-type all
network locations into the routing table
DYNAMIC ROUTING
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In dynamic routing, a protocol on one router
communicates with the same protocol running on
neighbor routers.
The routers then update each other about all the
networks they know about and place this information
into the routing table.
If a change occurs in the network, the dynamic
routing protocols automatically inform all routers
about the event.
THE ADMINISTRATIVE DISTANCE (AD)
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is used to rate the trustworthiness of routing
information received on a router from a neighbor
router. An administrative distance is an integer
from 0 to 255, where 0 is the most trusted and 255
means no traffic will be passed via this route.
Route Type
Connected
Static
Exterior Border Gateway Protocol (eBGP)
EIGRP (internal)
Open Shortest Path First Protocol (OSPF)
RIP
Administrative
Distance
0
1
20
90
110
120
If a router receives two updates listing the same
remote network,
 the first thing the router checks is the AD.
 If one of the advertised routes has a lower AD
than the other, then the route with the lowest AD
will be placed in the routing table.
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If both advertised routes to the same network
have the same AD, then routing protocol metrics
(such as hop count or bandwidth of the lines) will
be used to find the best path to the remote
network.
IN THE STATIC ROUTING :
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There is no overhead on the router CPU
Here the overhead on administrator so that any
change on the network the administrator had to add
or modify the route.
There is no bandwidth usage between routers.
It adds security because the administrator can choose
to allow routing access to certain networks only.
It’s not feasible in large networks because
maintaining it would be a full-time job in itself.
IN DYNAMIC ROUTING
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The overhead is on the router resources ( CPU,
RAM, Bandwidth …) ,but no overhead on
administrator.
The security is not guaranteed because you
cannot control the route .
It’s better for large networks.
CONFIGURING A STATIC ROUTE ON A ROUTER
Using two ways:
 The next-hop address
 The exit interface
 Example…
DYNAMIC ROUTING
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Dynamic routing is when protocols are used to
find networks and update routing tables on
routers.
There are three classes of routing protocols:
 Distance Vector: The distance-vector routing
algorithm passes complete routing table contents
to neighboring routers, which then combine the
received routing table entries with their own
routing tables to complete the router’s routing
table.
 Example: RIP and IGRP are distance-vector
routing protocols. They send the entire routing
table to directly connected neighbors.
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Link state:
 In link-state protocols, the routers each create
three separate tables.
 One of these tables keeps track of directly
attached neighbors,
 one determines the topology of the entire
internetwork,
 and one is used as the routing table.
 Example: OSPF
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Hybrid:
 In Hybrid protocols use aspects of both distance
vector and link state.
 Example, EIGRP. Some books said that EIGRP is
distance vector protocol.
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ROUTING INFORMATION PROTOCOL (RIP)
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Metric : RIP only uses hop count to determine the
best way to a remote network, but it has a
maximum allowable hop count of 15 by default,
meaning that 16 is deemed unreachable.
RIP has two versions:
classful routing
 which means that all devices in the network must
use the same subnet mask.
 classless routing.
 provides something called prefix routing and does
send subnet mask information with the route updates
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ROUTING LOOPS PROBLEM ??
HOW
RIP STOP ROUTING LOOPS?
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Maximum Hop Count (counting to infinity)
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Split Horizon
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Route Poisoning
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Holddowns
CONFIGURING A RIP ROUTE ON A ROUTER
 Example….
THANKS