Cisco CRS Carrier Routing System Multishelf System Site Planning Guide
Multishelf System Planning Considerations
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Table of Contents

Multishelf System Planning Considerations

Planning the Switch Fabric Configuration

Planning the Control Network

Planning the System Management Network

Multishelf System Cable Management

Planning the Cabling Runs

Fabric Cables

System Management Cables

Cable Management

Single-Shelf to Multishelf System Upgrade

Power Redundancy

Redundant Power Systems and Chassis Power Zones

Noise Control

Cisco Installation Services

System Testing, Certification, and Warranties

Multishelf System Planning Considerations

This chapter describes the system planning considerations for your Cisco CRS Multishelf System installation. It contains the following sections:


Note The information in this chapter should be reviewed by the multishelf system designer, network or system administrator, and network facilities personnel to ensure that the system configuration will be appropriate for your application needs. The review should occur far enough in advance of the multishelf system shipment to allow modifications to be made to the system layout and configuration (if necessary) before system installation.


Planning the Switch Fabric Configuration

The multishelf system switch fabric is made up of switch fabric cards in the LCCs and FCCs:

  • S13 fabric cards in the LCCs implement Stage 1 and Stage 3 of the switch fabric.
  • S2 fabric cards in the FCCs implement Stage 2 of the switch fabric.

The S13 cards in the LCCs are connected to the S2 cards in the FCC using optical array cables called fabric cables.

  • Each fabric card implements a single plane of the eight-plane switch fabric in a single-module configuration. A group of three fabric cards implements a single plane of the eight-plane switch fabric in a multi-module configuration.
  • There is a total of eight planes of switch fabric regardless of the number of FCCs. If there is more than one FCC, the eight switch fabric planes will be split evenly among the FCCs.

For cabling instructions, see Cisco CRS-1 Carrier Routing System Multishelf System Interconnection and Cabling Guide . For a list of items to consider as you plan the cable runs, see the “Fabric Cables” section.

Switch Fabric Considerations

Consider the following as you plan the switch fabric configuration for your multishelf system:

  • Determine the lengths of fabric cables that are needed to connect S2 and S13 fabric cards to each other. For cabling instructions, see Cisco CRS-1 Carrier Routing System Multishelf System Interconnection and Cabling Guide .

Figure 5-1 shows the optical array cabling for a single-FCC multishelf system with vertical cabling.

Figure 5-1 Single-Module Switch Fabric Plane—Vertical Cabling

 

Figure 5-2 shows the optical array cabling for a single-FCC multishelf system with horizontal cabling.

Figure 5-2 Single-Module Switch Fabric Plane—Horizontal Cabling

 


Note Figure 5-2 is a logical drawing and is not a physical layout drawing. The connectivity for LCC1 through LCC8 is the same as the connectivity for LCC0, as shown in Figure 5-2. See the Cisco CRS Carrier Routing System Multishelf System Interconnection and Cabling Guide for more information.


Planning the Control Network

The control network consists of two 22-port SCGE cards (CRS-FCC-SC-22GE= or CRS-FCC-SC-22GE-B=) installed in the FCC and cabled to each LCC in the system.


Note For redundancy, we strongly recommend using two 22-Port SCGE cards installed in each FCC. If you operate the multishelf system with a single card and that card fails, the multishelf system has no control network connectivity and the router fails.


As you plan the control network for your multishelf system, consider the following:

  • Each route processor (RP) in the multishelf system must be connected to both 22-port SCGE cards in the FCC(s).
  • Each 22-port SCGE card must form a full mesh to every other SCGE card in the multishelf system.

For instructions on how to cable the 22-port SCGE cards, see the Cisco CRS-1 Carrier Routing System Multishelf System Interconnection and Cabling Guide .

Planning the System Management Network

The system management network provides a path for the control traffic that is used to configure and manage the multishelf system. The system management network consists of console connections between each of the chassis and a system console, which is typically connected to a terminal server.

  • For the system management network, consider the following:

A console connection is recommended for each RP and 22-port SCGE card.

The console port does not support modem control or hardware flow control.

RPs and 22-port SCGE cards also have AUX ports, which Cisco TAC engineers use for troubleshooting problems.

Use straight-through EIA/TIA-232 cable (RJ-45 connectors) for console and AUX connections.

For instructions on how to cable the system management network, see the Cisco CRS-1 Carrier Routing System Multishelf System Interconnection and Cabling Guide .

Multishelf System Cable Management

A major site planning consideration is the cabling that connects the LCCs and FCCs to each other. Review all of the following sections for information about the issues to consider as you plan the cabling runs for your multishelf system.

For instructions on how to install system cables, see Cisco CRS-1 Carrier Routing System Multishelf System Interconnection and Cabling Guide .

Planning the Cabling Runs

Before system installation, you must determine how to run the fiber cables and system management cables to all chassis in the multishelf system. Following is a list of items to consider as you plan the cabling runs for your multishelf system:

  • Plan the cabling runs carefully and well in advance of the installation.
  • Try to minimize the complexity of cable runs and keep cables as short as possible.This helps to keep cable slack (excess cable) to a minimum so that it does not cause an obstruction.

Fabric cables connect the S2 and S13 switch fabric cards to each other.
24 cables for each LCC. For more information, see the “Fabric Cables” section.

System management cables connect the RPs on the LCC(s) to the 22-port SCGE cards on the FCC(s). For more information, see the “System Management Cables” section.

  • Create a diagram that shows the cabling runs for the multishelf system. Although this step is optional, such a diagram might be very useful.
  • Will cables be routed between different rooms or from other areas of the site into the installation room? If so, are there any special issues to consider as you plan these cabling runs? For example:

Do the cables run between different floors?

Are there any obstacles in the cable route (such as a firewall that the cable must be routed around)?

Will the cables be routed through overhead ceiling tiles? If so, have you planned the route and determined which ceiling tiles need to be removed to provide access?

Will the cables be routed beneath raised floors? If so, have you planned the route and determined which floor tiles need to be removed for access?

  • If you need to plan for high availability of the system, consider the following:

Can cables be routed through different areas of the site to reduce the possibility of a single point of failure?

Fabric Cables

Fabric cables connect the S13 fabric cards in the LCC to the S2 switch fabric cards in the FCC via the OIMs at the rear of the FCC. Each LCC in the multishelf system requires a set of 24 fabric cables. The following list describes the issues to consider as you work with fabric cables:

  • There are two types of fiber cables available:

General purpose fabric cables (LCC/M-FC-FBR-xx) carry a dual flame rating: general purpose and LSZH (low smoke zero halogen). These cables are designed to connect between an LCC and FCC in the free air of the room. Fabric cables must be routed within a room. Fabric cables are not rated for installation above ceilings, below floors, or through walls.

Riser fabric cables (LCC/M-FC-FBR-xxR) meet the OFNR riser cable flame rating. These cables are designed to connect between an LCC and an FCC, either in the free air within a room, or, through a riser access between building floors. Riser cables are not rated for installation in air plenum passages, nor are they designed for use in LSZH (low smoke zero halogen) applications.


Note For a complete list of fabric cables available, see Table A-4Appendix A, “Product IDs for the Cisco CRS Multishelf System.”


  • Do not put pressure on fabric cables, which can damage the cables over time. In addition, do not twist the cables or bend them beyond their minimum bend radius:
    1.25 inches (3.17 cm)—Controlled 90-degree bend. Each cable has a strain-relief support (or turn collar) with an attached strip of Velcro. The bend radius of the cable should be no smaller than the arc of this collar.
  • You might want to consider creating a diagram of the cable runs for the fabric cables to ensure that the cables are connected correctly during the system installation.

System Management Cables

As you plan the system management cabling for your multishelf system, consider the following:

  • For the connections to the 22-port SCGE cards, consider the following:

Use single mode LC to LC fiber-optic cable.

Each route processor (RP) in the multishelf system must be connected to the 22-port SCGE cards.

  • For system console cables, consider the following:

Use straight-through EIA/TIA-232 console cable (RJ-45 connectors).

A console connection is recommended to each RP and 2-port SCGE card.

RPs and DRPs (LCC) and 22-port SCGE cards (FCC) also have AUX ports, which Cisco TAC engineers use for troubleshooting.

  • For the alarm module cable, use shielded cable (which is required for EMC compliance).

Cable Management

As the size of the routing system increases, the cabling required for the chassis increases.

The cabling runs must be carefully planned. The basic configurations for various routing systems should be arranged to minimize the complexity and length of the cable runs. Precut and terminated cables are considered part of the basic configuration.

For further information, see the Cisco CRS Carrier Routing System Multishelf System Interconnection and Cabling Guide.

Single-Shelf to Multishelf System Upgrade

You can upgrade a Cisco CRS single-shelf system to a multishelf system while the system is running. This hot-upgrade procedure allows you to upgrade the system without disrupting service. For instructions, see the Cisco CRS-1 Carrier Routing System Multishelf System Upgrade and Conversion Guide .

Power Redundancy

This section describes the power redundancy features of the FCC. It describes the power zones in a chassis with fixed configuration power installed and provides pointers to information about how to install cards in the chassis to configure the chassis for high availability so that a power failure does not disrupt system operation.

Following is a list of tasks you can consider doing to configure your multishelf system, with a fixed configuration power system installed, for high availability (which helps to ensure that service is not disrupted due to failures):

  • Consider running the power cables from each of the two power sources along different routes through the facility or at the installation site.
  • Install S2 switch fabric cards in appropriate slots in an FCC with fixed configuration power shelves installed so that a power failure does not degrade switch performance. See the Cisco CRS Carrier Routing System Multishelf System Interconnection and Cabling Guide for more information.
  • Consider running user interface cables along different routes.
  • Consider installing a redundant LCC, whose user interface links mirror the links on the other LCC. This way, if something happens to one LCC, the links are still operational on the other LCC.

Note See the Cisco CRS Carrier Routing System 16-Slot Line Card Chassis Site Planning Guide for information about power zones in the LCC and how to install cards in the LCC to configure the chassis for high availability.


Redundant Power Systems and Chassis Power Zones

Each fixed and modular configuration power shelf is connected to a separate and independent power source (2N power redundancy). During normal operation when both power sources are operational, both sets of power shelves and power modules function together to power the chassis. If a power source fails, the other power source provides enough input power to power the chassis. This 2N power redundancy enables the chassis to operate despite the power failure.

In addition, chassis power zones distribute power throughout the chassis and provide redundant power to chassis slots. In the modular configuration power system, all power modules power all chassis power zones, as long as the zone circuit breaker is not tripped. In the fixed configuration power system, each power zone is powered by a set of power modules (one module from each power shelf). In each set of power modules (A0 and B0, A1 and B1, and A2 and B2) each power module is considered a backup for the other. Each set of power modules provides power to the same set of chassis power zones. If either power module fails, the other continues to provide power to those slots.

Although it is rare, a double-fault power failure causes power to be lost to a power zone, if a fixed configuration power system is installed. A double-fault failure occurs when a power module and its backup module both fail. The failure results in all power being lost to a set of chassis slots, which means that the components or cards installed in those slots lose power and stop functioning until one of the failed power modules is replaced.

In the modular configuration power system, all power modules power all chassis power zones, so a double-fault power failure cannot occur.

Therefore, a double-fault power failure can only occur when a fixed configuration power system is installed in the chassis.


Note To avoid network connectivity disruption due to a double-fault power failure, you should carefully consider the best placement of cards in the chassis. See the Cisco CRS Carrier Routing System Multishelf System Interconnection and Cabling Guide for information about how to install cards to avoid a disruption in service.


Noise Control

The multishelf system can generate large amounts of fan noise. The LCCs and FCCs have some built-in noise reduction, such as fan speed control. If the multishelf system is installed in an environment in which excessive noise could be harmful to personnel, some other noise reduction options could be attempted. Passive noise reduction could include the installation of foam panels to insulate the surrounding area from the noise.

Additional noise reduction measures have to be designed on an individual site basis.

Cisco Installation Services

Cisco or a Cisco partner can provide a complete installation service, from planning to power up. For information about Cisco or Cisco partner installation services, consult Cisco Customer Advocacy.

System Testing, Certification, and Warranties

After the routing system has been installed, it must be tested and certified. Consult Cisco Customer Advocacy for information about testing, certification, and warranties.