CISCO ROUTER CONFIGURATIONEng.Ola Abd El-Latif1st June 2010

INTRODUCTION TO WAN 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.

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 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.

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 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.

ROM (read-only memory)

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 )

Stores the Cisco IOS , Not erased when the router is reloaded

NVRAM (nonvolatile RAM)

Holds router (& switch) configurations Not erased when the router is reloaded Does not store an IOS.

Bootstrap

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.

POST (power-on self-test)

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.

Console port (used for configuring router)

Interfaces (or ports) – LAN/WAN connections

THE ROUTER BOOT SEQUENCE

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.

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.

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.

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.

The router will use this file to run the router.

The router should now be operational.

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: 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 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.

This page will introduce the console and auxiliary (AUX) ports, which are also known as the management ports.

These asynchronous serial ports are not designed as networking ports.

The console port is required for the configuration of the router.

Not all routers have an auxiliary port.

When the router is first put into service, there are no networking parameters configured.

MANAGEMENT PORT CONNECTIONS

DIRECT CONFIG.

CONSOLE PORT

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 The router can also be remotely configured

through the configuration port across an

IP network using Telnet or by dialing to a modem connected to the

console or auxiliary port on the router.

AUXILIARY PORT

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 in-band, 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.

CONFIGURING A SINGLE CISCO ROUTERRouter 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 : 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)

EXAMPLE:

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

Broadcast Domain #2(1) Router1 to Switch2 is a collision domain

(2) Switch2 to Router2 is a collision domain

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

Total Broadcast Domains = 3Total Collision Domains = 7

ETHERNET CABLING : Three types of Ethernet cables are available:

Straight-through cable Crossover cable Rolled cable

STRAIGHT-THROUGH CABLE Four wires are used in straight-through cable

to connect Ethernet devices. It is relatively simple to create this type.

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.

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.

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

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.

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 meaning that someone must hand-type all

network locations into the routing table

DYNAMIC ROUTING 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) 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 TypeAdministrative

DistanceConnected 0Static 1Exterior Border Gateway Protocol (eBGP) 20EIGRP (internal) 90Open Shortest Path First Protocol (OSPF) 110RIP 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.

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 : 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 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 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.

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

Hybrid: In Hybrid protocols use aspects of both distance

vector and link state. Example, EIGRP. Some books said that EIGRP is

distance vector protocol.

ROUTING INFORMATION PROTOCOL (RIP) 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

ROUTING LOOPS PROBLEM ??

HOW RIP STOP ROUTING LOOPS? Maximum Hop Count (counting to

infinity)

Split Horizon

Route Poisoning

Holddowns

CONFIGURING A RIP ROUTE ON A ROUTER

Example….

THANKS