Práctica 1

Dispositivos Para la interconexión de redes.

Objetivo:

El objetivo de la práctica 1 era el de conocer algunos dispositivos para la interconexión de redes, como lo son: repetidor, switch y router.
Desarmar los equipos y observar su arquitectura interna y sus componentes.

Material:

• Desarmadores
• Pinzas
• Cámara Fotográfica
• Equipos

Desarrollo:

Repetidor

El término repetidor tiene los siguientes significados normalizados:

1. Un dispositivo analógico que amplifica una señal de entrada, independientemente de su naturaleza (analógica o digital).
2. Un dispositivo digital que amplifica, conforma, retemporiza o lleva a cabo una combinación de cualquiera de estas funciones sobre una señal digital de entrada para su retransmisión.

Para nuestra práctica pudimos conocer un Repetidor Ethernet de la marca D-Link modelo DE-804.

Características:

· Es un repetidor coaxial de 4 puertos.

· Tiene 4 puertos seriales.

· Fuente de poder

· Tiene circuitería TTL.

· Tiene cristales generadores de frecuencia.

· No tiene microprocesadores

· No tiene memorias.

· Tiene cableado Ethernet 10base5

· Trabaja en la capa física del modelo OSI

Switch

Es un dispositivo digital de lógica de interconexión de redes de computadores que opera en la capa 2 (nivel de enlace de datos) del modelo OSI. Su función es interconectar dos o más segmentos de red, de manera similar a los puentes (bridges), pasando datos de un segmento a otro de acuerdo con la dirección MAC de destino de las tramas en la red. Se utilizan cuando se desea conectar múltiples redes, fusionándolas en una sola. Al igual que los puentes, dado que funcionan como un filtro en la red, mejoran el rendimiento y la seguridad de las LAN

Para nuestra práctica pudimos conocer un switch de 3ra generación.

Características:

· Lleva cierto nivel de procesamiento de las tramas.

· Cuenta con tres circuitos integrados de aplicación específica ASIC, que conmutan las tramas.

· Tiene un chip para la administración y el monitoreo.

· Es un switch de 12 puertos.

Router

Es un dispositivo de hardware para interconexión de red de ordenadores que opera en la capa tres (nivel de red). Un router es un dispositivo para la interconexión de redes informáticas que permite asegurar el enrutamiento de paquetes entre redes o determinar la ruta que debe tomar el paquete de datos.

Para nuestra práctica pudimos conocer un router/bridge IGS multiprotocolo Cisco, modelo IGS-R.

Características Router:

2 conexiones Ethernet y varias interfaces en series

2 Conexiones Ethernet y un puerto serial síncrono

Tiene los elementos de una PC:

· Procesador Motorola 68020

· Memoria RAM

· Almacenamiento en memoras EPROM

· Cristales generadores de señal

· Puerto de consola, Ethernet y señal

· Tiene microcódigo (el equivalente al BIOS) que se configura mediante dipswitch.

Características del procesador Motorola 68020:

· Type Microprocessor

· Manufacturing process VLSI technology

· Data bus width 32 bit

· Package 114-pin plastic Pin Grid Array, 1.36" x 1.36" (3.45 cm x 3.45 cm)

· Speed (MHz) 16.7

· Physical memory (GB) 4

· Virtual memory (GB) 4

· Level 1 cache size 256 Bytes code

· Floating Point Unit External - Motorola 68881

· V core (V) 5 ± 5%

· Min/Max operating temperature (°C) 0 - 70Max power dissipation (W) 2

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IGS configurations register

Appendix A describes the IGS hardware and software configuration registers, the factory default settings of each, and the procedures for changing those settings.

The hardware configuration register is an 8-bit mechanical switch located on the IGS backpanel. The 16-bit software configuration register resides in nonvolatile memory. The hardware configuration register setting has priority, and will override software configuration register settings if a conflict arises. To avoid such conflicts, only the software register settings that cannot be set by the hardware register are described in this appendix.

Use the processor configuration register information contained in Appendix A to do the following:

• Set a boot file name
• Define the Break key
• Control broadcast addresses
• Set the console baud rate
• Enable/disable a watchdog timer
• Determine the server response to a bootload failure
• Control factory diagnostic modes in the server

Figure A-1 shows the top side of the IGS processor card as viewed with the chassis front facing you.

Hardware Configuration Register

In the back of the chassis under the power switch is an 8-bit switch, the hardware configuration register. The least significant bit of the configuration register is the one labeled "0" in Figure A-2.

Hardware Configuration Bit Meaning

Bit Number	Meaning
00-03	Power-up default action *
04-05	Console line speed
06	Watchdog timer disabled
07	Run diagnostic tests and ignore NVM contents

* May be overridden by the boot system command.

Figure A-2 shows the hardware configuration register factory settings.

To set a bit to 1 (on), push the switch down. To clear a bit to 0 (off), push the switch up.

Figure A-2: IGS Hardware Configuration Register Factory Settings

To change configuration register settings, turn off the server, set or clear the bits, and restart the server. Configuration register changes only take effect when the server restarts; that is, when you switch the power off and on or when you issue a reload command from the console.

The lowest four bits of the hardware configuration register (bits 3, 2, 1, and 0) form the boot field. The boot field specifies a number in binary. If you set the boot field value to 0, you must boot the operating system manually by giving a b command to the system bootstrap program. If you set the boot field value to 1 (the factory default), the server boots using the default ROM software. If you set the boot field to any other bit pattern, the server uses the resulting number to form a boot file name for netbooting.

The server creates a boot file name as part of the automatic configuration processes. To form the boot file name, the server starts with Cisco, and links the octal equivalent of the boot field number, a dash and the processor type name. Table A-2 lists the default boot file names or actions for the IGS processor.

Default Boot File Names

Action/File Name	Bit 3	Bit 2	Bit 1	Bit 0
bootstrap mode	0	0	0	0
ROM software*	0	0	0	1
cisco2-igs	0	0	1	0
cisco3-igs	0	0	1	1
cisco4-igs	0	1	0	0
cisco5-igs	0	1	0	1
cisco6-igs	0	1	1	0
cisco7-igs	0	1	1	1
cisco10-igs	1	0	0	0
cisco11-igs	1	0	0	1
cisco12-igs	1	0	1	0
cisco13-igs	1	0	1	1
cisco14-igs	1	1	0	0
cisco15-igs	1	1	0	1
cisco16-igs	1	1	1	0
cisco17-igs	1	1	1	1

* This is the default boot configuration.

Bit 4 and bit 5 in the hardware configuration register determine the baud rate of the console terminal. Table A-3 shows the bit settings for the four available baud rates. The factory default is 9600 baud.

System Console Terminal Baud Rate Settings

Baud	Bit 5	Bit 4
9600	0	0
4800	0	1
2400	1	1
1200	1	0

Bit/ 6 disables the hardware watch-dog timer. This is in the event of a hardware problem causing the watchdog timer to be dysfunctional, which can prevent the unit from initializing. By factory default, bit 6 is cleared to 0.

Bit 7 enables the factory diagnostic mode in the server. Setting this bit causes the server to produce detailed CPU self-check messages, automatically prompt for interface addresses, not read configuration files or non-volatile memory, and automatically enable all diagnostic tracing modes. Clearing this bit (the factory default) causes the server to operate normally. Note that setting this switch and reloading your IGS is one way to rewrite your configuration information without using your privileged password.

Software Configuration Register

The IGS has a 16-bit software register which is written into the non-volatile memory.

Table A-4 indicates the meaning of each of the bits.
Software Configuration Bit Meaning

Bit Number	Meaning
00	Boot from ROM*
01-03	Name of file for Netbooting*
06	Watchdog timer disabled*
07	OEM bit enabled
08	Break Disabled
10	IP broadcast with all zeros
11-12	Console line speed*
13	Boot default ROM software if network boot fails
14	IP broadcasts do not have net numbers
15	Run diagnostic tests and ignore NVM contents*

* These bits are controlled by the hardware configuration register.

To change configuration register settings, use the config-register command documented below, and restart the server. Configuration register changes only take effect when the server restarts, that is, when you switch the power off and on or when you issue a reload command from the console.

In order to issue the configure or reload commands, you must first enable the privileged mode of operation. At the "GS>" prompt, type "enable." The system will prompt you for the privileged password. After the password has been correctly entered, the prompt will change to a pound sign (#). When you wish to exit the privileged mode, type "disable" at the prompt.

Use the config-registervalue configuration command to set the contents of the software configuration register. Value is a hexadecimal number preceded by "0x." The software configuration register is stored in nonvolatile memory, as there are no hardware jumpers available. For example, the default switch register contents can be set with the command "config-register 0x1." The new setting does not take effect until the IGS software is reloaded. The show hardware command will display the configuration register value stored for the next reload, as well as the value currently in effect.

Bit 8 controls the console Break key. Setting bit 8 (the factory default) causes the processor to ignore the console Break key. Clearing bit 8 causes the processor to interpret Break as a command to force the system into the bootstrap monitor, halting normal operation.

Bit 10 controls the host portion of the Internet broadcast address. Setting bit 10 causes the processor to use all zeros; clearing bit 10 (the factory default) causes the processor to use all ones. Bit 10 interacts with bit 14, which controls the network and subnet portions of the broadcast address. Table A-5 shows the combined effect of bits 10 and 14.

Configuration Register Settings for Broadcast Address Destination

Bit 14	Bit 10	Address ( )
off	off
off	on
on	on
on	off

Bit 13 determines the server response to a bootload failure. Setting bit 13 causes the server to load operating software from ROM after five unsuccessful attempts to load a boot file from the network. Clearing bit 13 causes the server to continue attempting to load a boot file from the network indefinitely. By factory default, bit 13 is cleared to 0.

Initialization and Self Test

The following tests are performed automatically each time the IGS is turned on or reinitialized.

Step 1: Reset the network A and B interfaces.

Step 2: Update the 16-bit software configuration register from the 8-bit hardware configuration register.

Step 3: Initialize the Universal Asynchronous Receiver Transmitter (UARTs).

Step 4: Print the sign-on message; for example:

System Bootstrap, Version 4.2(06)

Step 5: Exit boot state. While in boot state, reads to low memory get mapped to reads in ROM address space.

Step 6: Set and verify the bus error vector (this is the first time main memory is accessed).

Step 7: Fill low RAM from 0x10 to 0x1000 with 0x00000000.

Step 8: Verify that low RAM from 0x10 to 0x1000 is 0x00000000. Fill low RAM from 0x10 to 0x1000 with 0xFFFFFFFF.

Step 9: Verify that low RAM from 0x10 to 0x1000 is 0xFFFFFFFF.

Step 10: Fill low RAM from 0x10 to 0x1000 with address+1.

Step 11: Verify that low RAM has address+1 (assures unique addressability).

Step 12: Size memory by detecting bus errors and wraparound.

Step 13: Initialize the rest of RAM space.

Step 14: Copy MC68020 CPU exception vectors from ROM to RAM.

Step 15: Start the realtime clock.

Step 16: Perform the go/nogo test of realtime clock by ensuring that clock increments.

Step 17: Start watchdog timer (The card resets if the watchdog expires).

Step 18: Determine NVRAM size (there are versions of the IGS with 16 KB and 32 KB NVRAM).

Step 19: Search for a system image in ROM address space.

Step 20: Initialize ROM monitor variables.

Step 21: Read to identify our configuration for system software (1E1T or 2E).

Step 22: Save boots/reboot information for show hardware and show stacks.

Step 23: Light the OK LED.

Step 24: Return to the monitor routine which will boot a system image or start up the ROM monitor command interpreter.