building a cicso network for windows 2000 phần 8 pptx

394 Chapter 10 • Implementing the Cisco Switches

the two 100BaseTX ports as fast links to servers within the network that

are running 100BaseTX Ethernet cards. On the other hand, if the 1924

switch is one of several in a large network, an administrator might use

100BaseFX ports to hook into a fiber optic backbone for high-speed access

to the rest of the network. Table 10.2 lists the port configurations for the

1900 series of switches.

In addition to the ports listed in Table 10.2, all 19xx series switches

have one Ethernet AUI port in the back and one console port for configura￾tion. This can be used for Thinnet, Thicknet, Ethernet, or fiber-optic con￾nections.

The 19xx series can store up to 1024 MAC addresses in the Cisco

Access Manager (CAM) table. The entire architecture of the switch is linked

together by a 1-Gbps bus. All the 19xx Catalyst switches also have a 3MB

packet buffer for network surges. This reduces the chance that a switch

will drop a packet if it gets busy. All 1900 switches have room for a redun￾dant power supply for backup. For operational and status information, the

front of the 1900 series includes LED readouts for status indicators and

diagnostics.

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Table 10.2 Port Configurations for the Catalyst 1900 Series

Ports 1912 1912C 1924 1924C 1924F

10BaseT

100BaseTX

100BaseFX

12

2

0

12

1

1

24

2

0

24

1

1

24

0

2

Troubleshooting 101:

Basic Catalyst Issues

A green LED readout on a switch usually means everything is oper￾ational, amber means something may be interfering with a procedure,

and red means bad news. The idea is to become familiar with whether

an amber switch means something like an extra power supply, or if there

really is an issue with the switch. Many network problems are discovered

by a bright red light that you might notice while walking past your

For IT Professionals

Continued

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Implementing the Cisco Switches • Chapter 10 395

Hardware Features of the 2820 Series

The 2820 series consists of two models: the 2822 and 2828. However, the

2822 series has been discontinued by Cisco, so in the future, only the

2828 will be available. The 2820 series use the same 1-Gbps switching

fabric as well as the 3MB shared buffer used by the 1900 series. There are

really only two differences between the 2820 and 1900 series switches:

modular expansion and address storage.

The 2820 series offers a modular solution to small networks. The

design of the 2800 series consists of 24 10BaseT ports, one Ethernet AUI

port, and two expansion slots for modules. The 2820 expansion slots can

support the following modules:

■ The dual attachement station (DAS) fiber distributed data interface

(FDDI) Fiber module comes with two ports that use a ST Fiber￾Optic Connector.

■ The single attachement station (SAS) FDDI Fiber module has one

port that uses the ST Fiber-Optic Connector (these come in

medium and long-reach models).

■ The SAS FDDI User Datagram Protocol (UDP) module supports one

port with an RJ-45 connector.

■ 100BaseTX modules come with either one switched or eight shared

100Base TX ports.

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switches on a day-to-day job. For example, one of my first networking

duties involved going to three sites every morning with a checklist (to be

signed) and checking the routers, switches, and CSU/DSUs in the wiring

closets for red lights! However, when dealing with connectivity issues, a

green LED on a 19xx series port (and practically any hub/switch, for that

matter) is usually only an indication of Layer 2 (data link) connectivity.

Likewise, red lights are a sign of issues or malfunctions. Amber lights can

have various meanings, but usually refer to intermittent issues or

standby situations, such as a backup power supply or a port that is

being blocked by the Spanning Tree Protocol. Remember, when trou￾bleshooting connectivity issues, Cisco wants you to start at the physical

layer with the cable and switch, and work your way up.

There are several LEDs on the front of a 19xx/2820 series switch that

can keep you updated on the status of the switch and any issues that

might arise.

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396 Chapter 10 • Implementing the Cisco Switches

■ Likewise, 100BaseFX modules have either one switched or four

shared 100Base FX ports.

■ The Asynchronous Transfer Mode (ATM) 155 multimode (MM) and

single-mode (SM) Fiber Modules support one ATM interface using

SC Fiber-Optic Connectors.

■ The ATM 155 UDP module supports one ATM interface using the

RJ-45 standard.

The other difference between the 1900 series and the 2820 series is the

number of MAC addresses that can be stored in the CAM table. Whereas

the 1900 series can store only 1024 MAC addresses, the 2822 can store up

to 2048 MAC addresses, and the 2828 can store up to 8192 MAC

addresses.

Software Features of the 1900/2820 Series

There are two editions of the Cisco Switching operating system: Standard

and Enterprise. Some of the Standard edition IOS features for the

1900/2820 series are the following:

Cisco Visual Switch Manager A Web-based management system for basic

configuration of Cisco switches. A preconfigured IP address and inline con￾nection are required.

VLAN support Up to four VLANs can be configured per switch on the

1900/2820 series.

Network port A default port for the network (like a default gateway). It

serves as a final point of departure for unknown MAC addresses.

CGMP Cisco Group Multicast Protocol; a protocol used to manage multi￾casts on Catalyst switches.

Spanning Tree Protocol For management of redundant paths and

switching loops.

Three switching modes Cut-Through, Store-and-Forward, and

FragmentFree.

Fast EtherChannel and Gigabit EtherChannel A means of clustering

multiple links together to one source for faster performance than just one

link.

Remote monitoring (RMON) This switch can store RMON data for collec￾tion and analysis. RMON is a Request for Comments (RFC) established

protocol for network management and monitoring.

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Implementing the Cisco Switches • Chapter 10 397

For larger networks, the Enterprise edition software offers advanced

control, clustering, configuration, and authentication features required for

large-scale networks:

Increased VLAN support The Enterprise edition will support 64 VLANs

with Inter-Switch Link (ISL) and 802.1Q VLAN tagging. This edition also

supports the VLAN Trunking Protocol.

Uplink Fast A port feature for Catalyst switches that can reduce the time

taken for a port to upgrade from “blocking” to “forwarding” states.

TACACS+ (Terminal Access Controller Access Control System Plus)

Authorization support for devices on the switch. Instead of simply logging

in with a standard name and password on the switch, you can have the

switch refer to a TACACS+ server for authentication. This will ensure that

outside users won’t simply be logging in and guessing the password; they

would need an account on the TACACS+ server.

CLI An IOS-type configuration utility that can be used rather than the

menu-configuration features of the 1900/2820 series. The CLI is also used

for advanced configuration of the Enterprise edition features.

Catalyst 2900XL/3500XL

The 2900XL/3500XL series represents some of the newer access and dis￾tribution switches. These switches, developed by Cisco, take advantage of

newer technology and features like clustering and gigabit modules to

expand the speed and flexibility of desktop/enterprise switching.

NOTE

There are major differences between the 2900XL series (the 2912 and

2924) and the 2900G series that is based on the Catalyst 5000 switches

(the 2948G and now discontinued 2926G)—make sure you understand

the differences between the two models. This section will focus on the

2900XLs, and the 2900G series is covered with the Catalyst 5000s. There

is also an older model 3xxx (3000–3200) series that is different from the

3500XL series. In short, you will be hard pressed to find any rhyme or

reason for why some switches are named the way they are. One stan￾dard that Cisco has been using in creating its new line of gigabit

switches is ending them with the “G” designation (3508G/2948G);

modular switches usually end in “M,” and fiber-optic switches usually

end in “F.”

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398 Chapter 10 • Implementing the Cisco Switches

Gigabit Interface Converters (GBICs)

The Gigabit Interface Converter (GBIC) is a new IEEE (Institute of

Electrical and Electronics Engineers) technology that is designed to provide

a higher speed link between switches. GBICs are installed into slots and

work in a modular configuration. There are three types of GBIC modules

available for GBIC slots. Depending on variables like range, speed, and

usage in a cluster, they can transmit data at a range from 550 m to 100

km. (Performance will vary depending on physical factors like the quality of

cable and the wavelength used.)

■ 1000BaseSX (short wavelength) uses the multimode fiber-optic

link for data transmission. Depending upon the wavelength and

type of cable, data can be transmitted up to 550 meters.

■ 1000BaseLX/LH is a single-mode fiber-optic link that can transmit

up to 10 km.

■ 1000BaseZX can transmit in single mode up to 100 km with a

high-quality cable. Average quality will only transmit data about

70 km.

Cisco is designing new switches that use the GBIC standard for high￾speed connections to distribution and core layer switches. The 3500XL and

4000 series Catalyst switches all have switches with integrated GBIC ports,

and new modules bring GBIC compatibility to the Catalyst 5000. The new

Catalyst 6000 and 8500 series came out with GBIC modules already

designed and engineered for them. The older 1900 and 2820 series do not

have the capability to use GBIC modules.

Switch Clustering

Switch clustering is a means of combining Catalyst stacks under one IP

address and central control. Switch clustering is available on the

2900XL/3500XL series, and can be combined with 1900 and 2820

switches. Up to 16 switches can be connected under one cluster and man￾aged under one IP address. (Only nine GBIC switches can be included in

one cluster.)

All clusters start with a Command switch. This switch must be running

Catalyst software version 12.0(5) or later to serve as a Master switch. Only

the 2900XL and 3500XL series can serve as a Command switch. Higher￾level switches, including the 4000 series and the 3xxx (non-XL), cannot

function as a Command or Member switch. In addition to the IOS require￾ments, the switches must be running the Cisco Discovery Protocol (CDP),

and the ports that are connected must belong to the same management

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Implementing the Cisco Switches • Chapter 10 399

VLAN. Up to 16 switches, including 1900 and 2820s connected through

EtherChannel, can be managed in this way.

NOTE

Just because a switch can run as a Member switch doesn’t mean it will

work as a Command switch. Pay close attention to the requirements of

the Command switch. You can have a 2900XL switch enabled as a

Command switch at the top of a Gigastack bus because it’s running

12.0(5), and the switches below it could be running a lower version of

the Catalyst software that wouldn’t permit one of them to function as a

Command switch, although they will work as Member switches provided

they’re running cluster member software.

3500 series switches can also be stacked in a Gigastack. This is a high￾speed clustering of Gigabit-compatible switches linked together with GBIC

technology, either to each other in a bus topology, or with a Master switch

like the 3508G running the cluster in a hub-and-spoke topology. In this

case, the GBIC cable can only run a maximum of one meter between each

switch, and only nine switches can operate in a Gigastack. The actual

speed varies depending on the type of Gigastack built.

■ A bus Gigastack has each switch hooked in a line with the next

one. Each GBIC’s receive port is hooked up to the next GBIC’s

transmit port. The GBIC switch at the bottom hooks back up to

the top. In this configuration, 1 Gbps is distributed in the bus

among the entire stack. Because the switches are hooked in a

loop, there is a redundant path that can be brought up if a cable

or switch goes down.

■ A hub-and-spoke Gigastack has each GBIC switch hooked up to a

Master GBIC switch with several ports, such as a 3508G or the

4912G. In this case, the Master switch will deliver up to its max￾imum forwarded bandwidth within its internal switching fabric (up

to 5 Gbps on a 3508G, for example) with a 2-Gbps full-duplex con￾nection between each switch. Each GBIC’s Receive and Transmit

ports are cross-connected with the GBIC Receive and Transmit

ports on the other switch. This design lacks the redundancy of the

bus design, but is faster because each link is running in full￾duplex mode.

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