Different Catalyst switches support different power redundancy capabilities. This section describes the power redundancy capabilities of the medium and high end Catalyst switches, such as the Catalyst 4500 and Catalyst 6500 series switches, and low end switches, such as Catalyst 3750 series switches.
Catalyst 4500 and Catalyst 6500 Power Redundancy
In addition to supporting redundant Supervisor Engines, Catalyst 4500 and 6500 series switches also support redundant power supplies. The redundant power supplies must be identical, and possess the same power input and output ratings. Cisco IOS software support two power redundancy modes in Catalyst 4500 and Catalyst 6500 series switches:
- Combined
- Redundant
In combined mode, both power supplies are used at the same time by the switch. This means that the total power load required can exceed the maximum power output rating of one power supply but cannot exceed the sum of both power supplies.
When combined mode is used, the switch will power up as many modules as the combined capacity allows. However, in the event that one of the power supplies should fail and there is not enough power for all previously powered up modules, the system powers down the modules for which there is not enough power.
NOTE: Combined mode is typically used when the switch has a large amount of Power over Ethernet (PoE) modules, which may be used to provide power to IP phones or other devices, such as wireless access points. PoE will be described in detail in the following chapter.
In redundant mode, by default, the switch will draw its full power from both power supplies. Unlike combined mode, however, both power supplies only provide half of the required power each, meaning that the switch uses no more combined power than the maximum power capability of one of the single power supplies.
When one power supply fails, the other immediately takes over the full load, preventing the modules from being powered down or disabled due to insufficient power.
Configuring Catalyst 4500 and Catalyst 6500 Power Redundancy
The power redundancy mode is configured using the power redundancy-mode [combined | redundant] global configuration command. Example 8-69 below illustrates how to configure redundant power mode in a Catalyst 6500 series switch.
Example 8-69: Configuring Power Redundancy
| Catalyst-6500-1(config)# power redundancy-mode redundant Catalyst-6500-1(config)#exit |
This configuration is validated using the show power command and any applicable keywords, which are illustrated in Example 8-70.
Example 8-70: The show power Command
| Catalyst-6500-1#show power ? available System power available (margin) capabilities Show individual power supply capabilities detail Show detailed information on power resources inline Show inline power status module Show power consumed by modules status Show all power status supplies Show power supplies needed | Output modifiers <cr> |
Example 8-71 shows the output of the show power, which is used to verify the configured power redundancy method on the switch.
Example 8-71: Verifying the Power Redundancy Mode
| Catalyst-6500-1#show power system power redundancy mode = redundant system power total = 1153.32 Watts (27.46 Amps @ 42V) system power used = 397.74 Watts ( 9.47 Amps @ 42V) system power available = 755.58 Watts (17.99 Amps @ 42V) Power-Capacity PS-Fan Output Oper PS Type Watts A @42V Status Status State —- —————— ——- —— —— —— —– 1 WS-CAC-2500W 1153.32 27.46 OK OK on 1 WS-CAC-2500W 1153.32 27.46 OK OK on… [Truncated Output] … |
If mismatched, or different capability, power supplies are detected, the switch will disable one of them as shown in the output in Example 8-72.
Example 8-72: Verifying Mismatched Power Supplies
| Catalyst-4500-1#show power
Power Fan Inline … |
Catalyst 3750 Power Redundancy
Unlike the Catalyst 4500 and Catalyst 6500 series switches, Catalyst 3750 power redundancy is provided by an external power supply unit: the Cisco Redundant Power System (RPS) 2300.
The RPS 2300 contains two power supply bays and can provide complete internal power supply redundancy for up to two attached networking devices. The RPS 2300 can be combined with the Cisco Catalyst 3750-E and 3560-E PoE switches and any uninterruptible power supply (UPS) systems to provide protection against any one of the following:
- Internal power supply failures in network devices
- Failure of an AC circuit (a circuit breaker tripping, for example)
- Interruption of utility power