Installing the Switch Router

Site Planning

Rack-Mounting the Switch Router

Gigabit Interface Converter

Patch Cord

Differential Mode Delay

Installing and Removing GBICs

Installing GBICs

Removing GBICs

Connecting to the Gigabit Ethernet Ports

Connecting Power to the Switch Router

Front Panel LEDs

Installing the Switch Router

This chapter describes how to prepare your site for installation, as well as rack-mount the Catalyst 4908G-L3 switch router. It also provides Gigabit Interface Converter (GBIC) information and instructions for connecting power to the switch router. For first-time installations, perform the procedures in the following sections in the order listed here:

Warning Before you install, operate, or service the system, read the Site Preparation and Safety Guide. This guide contains important safety information you should know before working with
the system.

Site Planning

Planning the proper location and layout of your equipment rack or wiring closet is essential for successful switch router operation. Equipment placed too close together or in an inadequately ventilated area can cause system overtemperature conditions. In addition, poor equipment placement can make system panels inaccessible and difficult to maintain.

To ensure normal operation and avoid unnecessary maintenance, plan your site configuration and prepare your site before installation. For a description of the environmental monitor, see the "Power Supplies" section.

Table A-1 lists the operating and nonoperating environmental site requirements for the switch router. The environmental ranges are those within which the system continues to operate; however, a measurement that approaches the minimum or maximum of a range indicates a potential problem. You can maintain normal operation by anticipating and correcting environmental anomalies before they exceed the maximum operating range.

Verify the site power for the type of device you are installing. Power requirements are useful for planning the power distribution system needed to support the switch router. Heat dissipation is an important consideration for sizing the air-conditioning requirements for an installation. See Table A-1 for power and heat ratings for the switch router.

Caution Verify that the total maximum load on the circuit supplying power to the power supplies is within the current ratings of the wiring and breakers to prevent a loss of input power.

Note The redundant power option provides a second power supply to ensure that power to the switch router continues if one power supply fails or input power on one line fails. The redundant power supply provides this second feature only if the power supplies are connected to separate input lines.

Rack-Mounting the Switch Router

Before installing the switch router in a rack, read the Site Preparation and Safety Guide to familiarize yourself with proper site and environmental conditions.

You need the following tools to install the switch router in a rack:

A 3/16-inch flat-blade screwdriver
Four 12-24 x 3/4-inch screws
A tape measure and level

The following items are included in the accessory kit that ships with the chassis:

A rack-mount kit
- Two L brackets
- Eight Phillips M4 flathead screws
A disposable electrostatic discharge (ESD) grounding strap or ESD-preventive strap

Warning Unplug power cords before you work on a system that does not have an on/off switch.

To install the switch router in a rack, follow these steps:

Step 1 Prepare for installation as follows:

a. Place the switch router on the floor or on a sturdy table as close as possible to the rack. Leave enough clearance so that you can move around the switch router.

b. Use a tape measure to measure the depth of the rack. Measure from the outside of the front mounting posts to the outside of the rear mounting strip. The depth must be at least 18 inches (48.9 cm) but not greater than 32 inches (81.3 cm).

c. Measure the space between the inner edges of the left front and right front mounting posts to ensure that it is 17.75 inches (45.72 cm) wide.

Note Some equipment racks provide a power strip along the length of one of the rear posts. If the rack has this feature, consider the position of the strip when planning fastener points. Before installing the L brackets on the switch router, decide whether to install the switch router from the front or the rear of the rack.

Step 2 Remove the four (two on each side) M3 screws that are adjacent to the vent openings on the sides of the chassis. (See Figure 2-1.)

Figure 2-1: Removing the M3 Screws

Step 3 Attach the left and right L brackets using the eight (four on each side) flat-head Phillips screws provided in the rack-mount kit. (See Figure 2-2.)

Figure 2-2: Attaching the L Brackets to the Catalyst 4908G-L3

Step 4 Install the switch router in the rack as follows:

a. Insert the rear of the switch router between the mounting posts. (See Figure 2-3).

Figure 2-3: Installing the Catalyst 4908G-L3 in the Rack

b. Align the mounting holes in the L bracket with the mounting holes in the equipment rack.

c. Secure the switch router using four (two per side) 12-24 x 3/4-inch screws through the elongated holes in the L bracket and into the threaded holes in the mounting post. (See Figure 2-3.)

The switch router powers up when you plug in the power cord. See the "Connecting Power to the Switch Router" section for instructions.

Gigabit Interface Converter

A Gigabit Interface Converter (GBIC) is a hot-swappable input/output device that plugs into the Gigabit Ethernet port, linking the switch router with the fiber-optic network. (See Figure 2-4.) The following GBIC media types are supported:

1000BaseSX (short wavelength)
1000BaseLX/LH (long wavelength/long haul)
1000BaseZX (extended distance)

Figure 2-4: GBIC

Note Because of interoperability issues, Cisco does not support GBICs purchased from third-party vendors. See Table B-3 for GBIC port specifications.

Patch Cord

When using the 1000BaseLX/LH GBIC with 62.5-micron diameter multimode fiber (MMF), you must install a mode-conditioning patch cord between the GBIC and the MMF cable on both the transmit and receive ends of the link. You need the patch cord for link distances greater than 984 feet (300 meters). For link spans less than 300 meters, you can omit the patch cord.

The patch cord must comply with IEEE standards. The IEEE found that link distances did not meet with certain types of fiber-optic cable because of a problem in the center of some fiber-optic cable cores. The solution is to launch light from the laser at a precise offset from the center by using the patch cord. At the output of the patch cord, the 1000BaseLX/LH GBIC complies with the IEEE 802.3z standard for 1000BaseLX. For a detailed description of this problem, refer to the "Differential Mode Delay" section.

Note Cisco Gigabit Ethernet products have been tested and evaluated to comply with the standards listed in "Port Pinouts." Equivalent cables should also meet these standards.

Plug the end of the patch cord labeled "To equipment" into the GBIC (see Figure 2-5). Plug the end labeled "To cable plant" into the patch panel. The patch cord is 9.84 feet (3 meters) long and has duplex SC-type male connectors at each end.

Figure 2-5: Installing the Patch Cord

Differential Mode Delay

When an unconditioned laser source (1000BaseLX/LH GBIC) designed for operation on single-mode fiber (SMF) cable is directly coupled to an MMF cable, differential mode delay (DMD) can occur. DMD can degrade the modal bandwidth of the fiber-optic cable causing a decrease in the link span (the distance between the transmitter and the receiver) that is reliably supported.

The Gigabit Ethernet specification (IEEE 802.3z) outlines parameters for Ethernet communications at a gigabits per second rate. The specification offers a higher speed version of Ethernet for backbone and server connectivity using existing deployed MMF cable. To accomplish this, the specification defines the use of laser-based optical components to propagate data over MMF cable.

Lasers function at the baud rates and longer distances required for Gigabit Ethernet. The IEEE 802.3z Gigabit Ethernet Task Force has identified the DMD condition that occurs in certain circumstances with particular combinations of lasers and MMF cable. The resulting characteristics create an additional element of "jitter" that limits the reach of Gigabit Ethernet over MMF cable.

With DMD, a single laser light pulse excites a few modes equally within an MMF cable. These modes, or light pathways, then follow two or more different paths. These paths may be of different lengths and have different transmission delays as the light travels through the cable. With DMD, a distinct pulse propagating down the cable no longer remains a distinct pulse or, in extreme cases, can become two independent pulses. Strings of pulses tend to interfere with each other making it difficult to recover data in a reliable fashion.

DMD does not occur in all deployed fibers. It occurs with certain combinations of worst-case fibers and worst-case transceivers. Gigabit Ethernet is the first technology to experience this problem because of its very high baud rate and its long MMF cable lengths. SMF cable and copper cable are not affected by DMD.

MMF cable has only been tested for use with LED sources. LEDs create a condition within a fiber-optic cable referred to as an overfilled launch condition. The overfilled launch condition describes the way LED transmitters couple light into the fiber-optic cable in a broad spread of modes. Similar to a light bulb radiating light into a dark room, the generated light shines in multiple directions that "overfill" the existing cable space and "excites" a large number of modes (see Figure 2-6).

Figure 2-6: LED Transmission Compared to Laser Transmission

Lasers launch light in a more concentrated fashion. Typically, a laser transmitter couples light into only a fraction of the existing modes or optical pathways in the fiber-optic cable (see Figure 2-6).

The solution to DMD is to condition the laser light launched from the source (transmitter) so it spreads the light evenly across the diameter of the fiber-optic cable making the launch look more like an LED source to the cable. The objective is to scramble the modes of light to distribute the power more equally in all modes. This prevents the light from being concentrated in just a few modes. This is in contrast to an unconditioned launch, which, in the worst case, might concentrate all of its light in the center of the fiber-optic cable, thereby exciting only two or more modes equally.

A significant variation in the amount of DMD is produced from one MMF cable to the next. No reasonable test can be performed to survey an installed cable plant to assess the effect of DMD. Therefore, you must use the mode-conditioning patch cords for all 1000BaseLX/LH GBICs using MMF when the link span exceeds 984 feet (300 meters). For link spans less than 300 meters, you can omit the patch cord .

Installing and Removing GBICs

This section describes how to install, maintain, and remove GBICs. Read the installation information in this section before you install a GBIC.

Caution If a 1000BaseLX/LH GBIC designed for operation on single-mode fiber (SMF) cable is directly coupled to a multimode fiber (MMF) cable, DMD can occur. See the "Differential Mode Delay" section.

Caution Unnecessary insertion or removal of a GBIC could lead to premature failure of the GBIC. A GBIC has a lifetime of 100 to 500 insertions or removals.

Follow these GBIC care and handling guidelines:

GBICs are static sensitive. To prevent ESD damage, follow your normal board and component handling procedures.

GBICs are dust sensitive. When the GBIC is stored or when a fiber-optic cable is not plugged in, keep plugs in the GBIC optical bores. (See Figure 2-7.)
The most common source of contaminants in the optical bores is debris picked up on the ferrules of the optical connectors. Use an alcohol swab or Kim-Wipe to clean the ferrules of the optical connector.

Figure 2-7: GBIC Optical Bore and Ferrule

Installing GBICs

The switch router ships without GBICs installed.

Caution When inserting or removing a GBIC, always wear an ESD wrist strap connected to the ESD wrist strap connector.

Note GBICs are hot-swappable.

To install a GBIC, follow these steps:

Step 1 If the port you are removing the GBIC from is not in the administratively down state, enter the shutdown command.

Step 2 Remove the GBIC from its protective packaging.

Step 3 Verify that the GBIC is the correct type for your network by checking the part number. The part number indicates whether it is 1000BaseSX, 1000BaseLX/LH, or 1000BaseZX.

Step 4 Grip the sides of the GBIC with your thumb and forefinger; insert the GBIC into the slot on the front of the module (see Figure 2-8).

Figure 2-8: Installing a GBIC

Note GBICs are keyed to prevent incorrect slot insertion.

Step 5 Slide the GBIC into the slot until you hear a click. The click indicates the GBIC is locked into the slot.

Step 6 Remove the plugs from the GBIC when you are ready to attach the fiber-optic cable. Save the plugs for future use.

Step 7 If you entered the shutdown command in Step 1, enter the no shutdown command after attaching the fiber-optic cables.

Caution Do not remove the plugs from the GBIC optical bores or the fiber-optic cable until you are ready to connect the cable. The plugs protect the GBIC optical bores and cable from contamination.

Removing GBICs

Note If you are removing the GBIC from an online switch router, enter the show interface command to verify the type of GBIC that is installed.

To remove a GBIC, follow these steps:

Step 1 If the port you are removing the GBIC from is not in the administratively down state, enter the shutdown command.

Step 2 Disconnect the fiber-optic cable from the GBIC SC-type connector.

Step 3 Release the GBIC from the slot by simultaneously squeezing the plastic tabs (one on each side of the GBIC).

Step 4 Pull the GBIC out of the slot.

Step 5 Install the plugs in the GBIC optical bores, and place the GBIC in protective packaging.

Step 6 If you entered the shutdown command in Step 1, enter the no shutdown command after attaching the fiber-optic cables.

Connecting to the Gigabit Ethernet Ports

To connect to the Gigabit Ethernet ports, follow these steps:

Step 1 Remove the plugs from the GBIC optical bores; store them for future use.

Step 2 Remove the plugs from the SC-type connector on the fiber-optic cable. Insert the connector into the GBIC. (See Figure 2-9).

Note When you plug the SC-type connector into the GBIC, make sure that both the Tx and Rx fiber-optic cables are fully inserted into the SC-type connector.

Note If you are using the 1000BaseLX/LH GBIC with MMF, you must install a patch cord between the GBIC and the MMF cable. See the "Patch Cord" section.

Figure 2-9: SC-Type Connector

Connecting Power to the Switch Router

To connect power to the switch router, follow these steps.

Step 1 Ensure that all site power and grounding requirements described in the Site Preparation and Safety Guide have been met prior to connecting the chassis to a power source.

Step 2 Plug the power cord into the power cord connector located at the right of the back panel.

Step 3 Connect the other end of the power cord to a power source.

Step 4 Verify power supply operation by checking the front panel power supply LEDs. See Table 2-1 for LED descriptions.

See "Troubleshooting the Switch Router," if the LEDs indicate a power or other switch router problem.

To connect the switch router to a Cisco RPS, refer to the Cisco Redundant Power System Hardware Installation Guide.

Front Panel LEDs

The LEDs on the front panel of the switch router perform the following functions:

Status LED indicates the operating state of the switch router.
Link status LEDs indicates the port status of the Gigabit Ethernet.
PS1 LED indicates the status of the internal power supply.
RPS LED indicates the status of the external redundant power supply.

The status LED is located at the bottom left of the front panel. The eight Gigabit Ethernet ports are numbered 1 through 8 and have a link status LED below each port. Figure 2-10 and Figure 2-11 show the location of the LEDs on the front panel. See Table 2-1 for LED descriptions.

Figure 2-10: Catalyst 4908G-L3 Port Numbering and LED s

The PS1 and RPS LEDs are near the auxiliary and console ports at the far right of the front panel. (See Figure 2-11.)

Figure 2-11: Catalyst 4908G-L3 Gigabit Ethernet Ports and LEDs

Table 2-1 describes the LEDs.

Table 2-1: LED Descriptions

LED State Description

Status

Green
Red
Orange
Off

The switch router performs a series of self-test diagnostics:
All tests pass
A test other than an individual port test fails
Switch router boot or diagnostic tests in progress
Switch router is disabled

Link status

Green
Off

Operational
No signal detected, or link configuration fails

PS1

Green
Yellow

Operational
PS1 not functional

RPS

Green
Yellow
Off

Operational
RPS present but not functional
Not installed or not in use

LED	State	Description
Status	Green Red Orange Off	The switch router performs a series of self-test diagnostics: All tests pass A test other than an individual port test fails Switch router boot or diagnostic tests in progress Switch router is disabled
Link status	Green Off	Operational No signal detected, or link configuration fails
PS1	Green Yellow	Operational PS1 not functional
RPS	Green Yellow Off	Operational RPS present but not functional Not installed or not in use

Table of Contents

Installing the Switch Router