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This chapter provides specific information about preparing your site for installation of the Cisco 12008 router. Included are safety guidelines, specific preparatory information, and tools and parts required to ensure successful installation of your router.
To prevent damage to the router, do not remove it from the shipping container until you have decided upon an installation location and are ready to install the router.
To unpack the router, use the document entitled Cisco 12008 Gigabit Switch Router System Packing and Unpacking Instructions that was shipped with your router. Inspect all items for shipping damage; if any damage is evident, immediately contact a Cisco customer service representative.
The following sections are included in this chapter:
Before attempting to install your router, consider the power and cabling requirements that must be satisfied, the equipment that you will need to install the router, and the environmental conditions that your site must meet.
The following guidelines are provided to help ensure your safety and to protect the equipment. This list may not identify all potentially hazardous situations in your working environment, so be alert and exercise good judgment at all times.
Before installing the router, ensure that your site is prepared properly so that you can avoid having to move the router later to accommodate the availability/proximity of power sources and network interface connections.
Whenever you lift or move the router (or any other heavy object), observe the following guidelines:
 | Caution Never attempt to lift, tilt, or move the router using the carrying handles on the AC-input and DC-input power supplies. These handles are meant to help you carry the power supplies; they are not designed to support the weight of the router. |
The line cards, a redundant CSC, the SFCs, the fan trays, and a redundant power supply can be removed and replaced while the system is running. In removing such components, there is no danger that an electrical hazard or system damage will result.
Observe the following basic guidelines when working with any electrical equipment:
In addition, observe the following guidelines when working with any equipment that is disconnected from a power source, but still connected to telephone or network wiring:
Many router components are sensitive to damage from static electricity. Some components can be degraded by exposure to as little as 30 volts. You can generate static voltages as high as 35,000 volts just by handling plastic or foam packing material, or by sliding an electronic assembly across plastic or carpeting. Failure to exercise proper electrostatic discharge damage (ESD) precautions can result in intermittent or complete failures of components.
To minimize the potential for ESD damage to electronic components, observe the following guidelines:
| Caution For safety, periodically check the resistance value of the antistatic strap. The resistance measurement should be between 1 and 10 megohms. |
 | Warning Because invisible laser radiation may be emitted from the aperture of the port when no cable is connected, avoid exposure to laser radiation and do not stare into open apertures. |
Before installing the Cisco 12008 router, review the guidelines presented in the following sections.
Before installing the Cisco 12008 in a telco-style or 19-inch equipment rack, consider the following rack-mounting guidelines:
The rack-mounting hardware included with the Cisco 12008 is suitable for most 19-inch equipment racks or telco-style racks. We strongly recommend a rack-mount installation for your router, due to size and weight considerations.
The specific rack-mounting guidelines for your router follow:
Figure 2-1 shows the outer dimensions of the Cisco 12008 enclosure.
The Cisco 12008 air circulation system includes two fan trays:
To ensure adequate air flow through the router's internal components, it is recommend that you maintain a clearance of at least 6 inches (15.4 cm) in the front and back of the router enclosure at all times.
If airflow through the router is blocked or restricted, or if the ambient air being drawn into the router is too warm, an overtemperature condition within the router can occur. Under extreme conditions, the router's environmental monitoring (MBus) system shuts down system power to protect internal electronic components from thermal damage.
The site should be as dust-free as possible. Dust tends to clog the air filter, reducing the flow of cooling air through the system and increasing the risk of an overtemperature condition.
For the operating and nonoperating environmental specifications for the Cisco 12008, refer to Table 1-9 in Chapter 1. The router operates within the ranges specified in this table; however, a temperature that approaches a minimum or maximum level indicates a potential problem. You can maintain normal system operations by anticipating and correcting environmental anomalies before they approach a critical state.
The environmental monitors built into the Cisco 12008 protect system components from potential damage from overvoltage and overtemperature conditions. To ensure normal operations and avoid unnecessary maintenance, plan and prepare your site properly before installing the router.
The Cisco 12008 router can be configured with either AC-input or DC-input power supplies.
A minimally configured router has one AC-input power supply or one DC-input power supply. Site requirements for the power supplies differ, depending on the type of source voltage required for the installed power supply(ies).
Observe the following general precautions and recommendations in planning the source power requirements for your router:
In a router to be equipped with AC-input power supplies, observe the following guidelines:
For a listing of the electrical specifications for the AC-input power supply, see Table 1-7 in Chapter 1.
Figure 2-5 lists the source AC power cords available for the Cisco 12008.
Table 2-1 lists the international options available for the source AC power cords.
| Label | Description | Product Number |
|---|---|---|
| United States | 208 VAC, 60 Hz AC power cord | CAB-GSR12-US= |
| Australian | 240 VAC, 50 Hz AC power cord | CAB-GSR12-AU= |
| European | 230 VAC, 50 Hz AC power cord | CAB-GSR12-EU= |
| Italian | 220 VAC, 50 Hz AC power cord | CAB-GSR12-IT= |
| United Kingdom | 240 VAC, 50 Hz AC power cord | CAB-GSR12-UK= |
In a router to be equipped with DC-input power supplies, observe the following guidelines:
For a listing of the electrical specifications for the DC-input power supply, see Table 1-8 in Chapter 1.
Figure 2-6 shows the specifications of the lug used for source DC power cable connections.
Each set of power terminals on the DC-input power supply faceplate consists of two 6-mm, metric-threaded, nickel-plated brass studs centered 0.625 inch apart. The earth ground studs extend 0.52 inch (13.2 mm) above the power supply faceplate; the set of positive (+) and negative (-) studs extend 0.9 inch (22.9 mm) above the faceplate. The nickel plating on the studs enhance their conductivity and ensure corrosion resistance.
For convenience, the lockwashers and nuts for connecting the source DC cables to the nickel-plated brass studs are loosely mounted on the studs ready for use.
In making source DC connections to the power supply, use the power cables and lugs having the specifications outlined in Table 2-2. An equivalent 2-hole lug is acceptable as a substitute for the Panduit DC power cable lug.
| Characteristic | Specification |
|---|---|
| DC power cable size | #4 AWG, high strand count copper wire |
| DC power cable lug | Panduit copper, standard barrel, 2-hole lug--Type LDC (Panduit part number: LCD4-14A-L). An equivalent 2-hole lug is acceptable as a substitute for the Panduit part. |
Two system (earth) grounding holes are provided on each side panel of the router enclosure, approximately 3 inches from the bottom rear of the panel (Figure 2-7).
To make an adequate grounding connection, you will need the following parts:
The procedure for connecting system ground to your router is presented in Chapter 3 in the section entitled "Connecting System Ground."
This section presents guidelines for setting up site wiring and cabling for your router. When planning the location for your router, you should take into account the following:
When wires are run for any significant distance in an electromagnetic field, interference can occur between the electromagnetic field and the signals on the wires. Be aware of the following points:
If wires exceed recommended distances, or if wires pass between buildings, give special consideration to the effect of a lightning strike in your vicinity. The electromagnetic pulse (EMP) caused by lightning or other high-energy phenomena can easily couple enough energy into unshielded conductors to destroy electronic devices. If you have had problems of this kind in the past, you may want to ask experts for assistance in electrical surge suppression and shielding.
Most data centers cannot resolve the infrequent, but potentially catastrophic, problems described above without pulse meters and other special equipment. Such problems are difficult to identify and resolve, so take precautions by providing a properly grounded and shielded environment, paying special attention to issues regarding electrical surge suppression.
The Synchronous Optical Network (SONET) specification for fiber-optic transmission defines two types of fiber:
Data transmission in either mode occurs by means of bundles of light rays that enter the fiber at a particular angle.
Single-mode fiber allows only one mode of light to propagate through the fiber; multimode fiber allows multiple modes of light to propagate through the fiber.
Multiple modes of light propagating through the fiber travel different distances, depending on entry angles, causing the light to arrive at destinations at different times. This phenomenon is called modal dispersion.
Single-mode fiber provides higher-bandwidth transmission and supports greater cable distances than multimode fiber. Table 2-3 lists the maximum distances for single-mode and multimode fiber-optic transmissions, as defined by SONET.
If the distance between two connected stations is greater than the maximum distance specified in Table 2-3, significant signal loss can result, making fiber-optic transmission unreliable.
| Transceiver Type | Maximum Distance between Stations1 |
|---|---|
| Single-mode | Up to 9 miles (14.5 km) |
| Multimode | Up to 1.5 miles (2.4 km) |
To design an efficient optical data link, you must evaluate the power budget.
The power budget represents the amount of light that must be available to overcome attenuation in the optical link and to exceed the minimum power required by the receiver to operate within specifications. Proper operation of an optical data link depends on modulated light reaching the receiver with enough power to be correctly demodulated.
The following variables reduce the power of the signal (light) transmitted to the receiver in multimode transmission:
Attenuation is significantly lower for optical fiber than for other media.
For multimode transmission, chromatic and modal dispersion reduce the available power of the system by what is referred to as the combined dispersion penalty (in decibels [dB]). The power lost over the data link is the sum of the attenuation losses, dispersion losses, and modal losses.
Table 2-4 lists the attenuation and dispersion limits for typical fiber-optic cable.
| Factor | Single-Mode | Multimode |
|---|---|---|
| Attenuation | 0.5 dB | 1.0 dB/km |
| Dispersion limit | No limit | 500 MHz/km1 |
The LED used for a multimode transmission light source creates multiple propagation paths of light, with each path having a different path length and time requirement to cross the optical fiber. This causes signal dispersion (smear).
Higher order loss (HOL) results from light from the LED entering the fiber and being radiated into the fiber cladding. A worst-case estimate of power margin (PM) for multimode transmissions is based on assumptions of minimum transmitter power (PT), maximum link loss (LL), and minimum receiver sensitivity (PR). The worst-case analysis provides a margin of error, because not all parts of an actual system will operate at worst-case levels.
The power budget (PB) is defined as the maximum possible amount of power transmitted. The following equation shows the calculation of the power budget:
The power margin is equal to the power budget minus the link loss:
If the power margin is positive, as a rule, the fiber-optic link will work satisfactorily.
Table 2-5 lists the factors that contribute to link loss and the estimate of the link loss value attributable to the link loss factors.
| Link Loss Factor | Estimate of Link Loss Value |
|---|---|
| Higher order mode losses | 0.5 dB |
| Clock recovery module | 1 dB |
| Modal and chromatic dispersion | Depends on fiber and wavelength used |
| Connector | 0.5 dB |
| Splice | 0.5 dB |
| Fiber attenuation | 1 dB/km |
Subtracting the data link loss from the power budget should produce a result greater than zero. If a result is less than zero, you may have insufficient power for receiver operation.
For SONET line cards, the signal must meet the signal requirements listed in Table 2-6.
| Characteristic | Single-Mode | Multimode |
|---|---|---|
| Minimum transmitter power (PT) | -18.5 | -15 |
| Minimum receiver sensitivity (PR) | -30 | -28 |
| Power Budget (PB) | -11.5 | -13 |
This section contains a sample calculation of a multimode power budget, based on the following variables:
Estimate the power budget, as follows:
The resulting power budget (PB) value of 5 dB indicates that this link would have sufficient power for fiber-optic transmission.
Below is a multimode power budget example based on the same parameters as in the previous example, but with a multimode link distance of 4 km:
The resulting power budget (PB) value of 4 dB indicates that this link would have sufficient power for transmission; however, due to the dispersion limit on the link (4 km x 155.52 MHz > 500 MHz/km), this link would not work with multimode fiber. In this case, single-mode fiber would be the better choice.
The single-mode signal source for fiber-optic transmission is an injection laser diode.
Single-mode transmission is useful for longer distances because a single transmission path within the fiber is used and smear does not occur. In addition, chromatic dispersion is reduced because laser light is essentially monochromatic.
The maximum overload limit on the single-mode receiver is -14 dBm. The single-mode receiver can be overloaded when short lengths of fiber are used because the transmitter can transmit up to -8 dB. The receiver could be overloaded at -14 dB, but no damage will result.
To prevent overloading the receiver when you are interconnecting short fiber links, insert a 5 to 10 dB attenuator on the link between any single-mode SONET transmitter and the receiver.
The following example of a single-mode power budget is for two buildings, 11 kilometers apart, that are connected through a patch panel in an intervening building. The entire link is made up of 12 connectors.
Estimate the power budget as follows:
The resulting power budget (PB) value of 1 dB indicates that this link would have sufficient power for transmission and would not exceed the maximum receiver input power.
Statistical models are more accurate in determining the power budget than "worst-case" methods.
Determining the link loss with statistical methods requires accurate knowledge of variations in the data link components. However, statistical power budget analysis is beyond the scope of this document.
For further information on this topic, refer to the UNI Forum specifications, ITU-T standards, and your equipment specifications.
The Cisco 12008 can be installed with a minimum number of tools:
If you do not receive everything you ordered, contact a Cisco customer service representative for assistance.
It is good practice to use a site log to record all actions taken relevant to router operation and maintenance. Keep the site log near the router for ready access by the site manager or other personnel.
Site log entries might include the following:
Figure 2-8 is an example of a typical site log. You can use this one or design one of your own that meets the needs of your particular site.
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