Software Entitlements. Support Contract. IP Services. Unlimited maintenance updates. The switch performs power-accounting calculations when a port is granted or denied power to keep the power budget up to date. After power is applied to the port, the switch uses CDP to determine the actual power consumption requirement of the connected Cisco powered devices, and the switch adjusts the power budget accordingly. This does not apply to third-party PoE devices.
The switch processes a request and either grants or denies power. If the request is granted, the switch updates the power budget. If the request is denied, the switch ensures that power to the port is turned off, generates a syslog message, and updates the LEDs.
Powered devices can also negotiate with the switch for more power. If the switch detects a fault caused by an undervoltage, overvoltage, overtemperature, oscillator-fault, or short-circuit condition, it turns off power to the port, generates a syslog message, and updates the power budget and LEDs.
The switch supports these PoE modes:. If the switch has enough power for all the powered devices, they all come up. If enough power is available for all powered devices connected to the switch, power is turned on to all devices.
If there is not enough available PoE, or if a device is disconnected and reconnected while other devices are waiting for power, it cannot be determined which devices are granted or are denied power. If granting power would exceed the system power budget, the switch denies power, ensures that power to the port is turned off, generates a syslog message, and updates the LEDs. After power has been denied, the switch periodically rechecks the power budget and continues to attempt to grant the request for power.
If a device being powered by the switch is then connected to wall power, the switch might continue to power the device. The switch might continue to report that it is still powering the device whether the device is being powered by the switch or receiving power from an AC power source.
If a powered device is removed, the switch automatically detects the disconnect and removes power from the port. You can connect a nonpowered device without damaging it. You can specify the maximum wattage that is allowed on the port. If the IEEE class maximum wattage of the powered device is greater than the configured maximum value, the switch does not provide power to the port. If the switch powers a powered device, but the powered device later requests through CDP messages more than the configured maximum value, the switch removes power to the port.
The power that was allocated to the powered device is reclaimed into the global power budget. If you do not specify a wattage, the switch delivers the maximum value.
Use the auto setting on any PoE port. The auto mode is the default setting. However, if the powered-device IEEE class is greater than the maximum wattage, the switch does not supply power to it. If the switch learns through CDP messages that the powered device needs more than the maximum wattage, the powered device is shut down.
If you do not specify a wattage, the switch pre-allocates the maximum value. The switch powers the port only if it discovers a powered device. Use the static setting on a high-priority interface. When policing of the real-time power consumption is enabled, the switch takes action when a powered device consumes more power than the maximum amount allocated, also referred to as the cutoff-power value.
When PoE is enabled, the switch senses the real-time power consumption of the powered device. The switch monitors the real-time power consumption of the connected powered device; this is called power monitoring or power sensing.
The switch also polices the power usage with the power policing feature. Power monitoring is backward-compatible with Cisco intelligent power management and CDP-based power consumption.
It works with these features to ensure that the PoE port can supply power to the powered device. The switch senses the real-time power consumption of the connected device as follows:. The switch monitors the real-time power consumption on individual ports. The switch records the power consumption, including peak power usage.
If power policing is enabled, the switch polices power usage by comparing the real-time power consumption to the maximum power allocated to the device. If the device uses more than the maximum power allocation on the port, the switch can either turn off power to the port, or the switch can generate a syslog message and update the LEDs the port LED is now blinking amber while still providing power to the device based on the switch configuration.
By default, power-usage policing is disabled on all PoE ports. If error recovery from the PoE error-disabled state is enabled, the switch automatically takes the PoE port out of the error-disabled state after the specified amount of time. If error recovery is disabled, you can manually re-enable the PoE port by using the shutdown and no shutdown interface configuration commands.
If policing is disabled, no action occurs when the powered device consumes more than the maximum power allocation on the PoE port, which could adversely affect the switch. When power policing is enabled, the switch determines one of the values as the cutoff power on the PoE port in this order:. Manually when you set the user-defined power level that the switch budgets for the port by using the power inline consumption default wattage global or interface configuration command. Manually when you set the user-defined power level that limits the power allowed on the port by using the power inline auto max max-wattage or the power inline static max max-wattage interface configuration command.
Automatically when the switch sets the power usage to be the default value of mW. Use the first or second method in the previous list to manually configure the cutoff-power value by entering the power inline consumption default wattage or the power inline [ auto static max ] max-wattage command. If you are not manually configuring the cutoff-power value, the switch automatically determines the value by using CDP power negotiation or the device IEEE classification, which is the third method in the previous list.
If the switch cannot determine the value by using one of these methods, it uses the default value of mW the fourth method in the previous list. You can configure the initial power allocation and the maximum power allocation on a port. However, these values are only the configured values that determine when the switch should turn on or turn off power on the PoE port.
The maximum power allocation is not the same as the actual power consumption of the powered device. The actual cutoff power value that the switch uses for power policing is not equal to the configured power value. When power policing is enabled, the switch polices the power usage at the switch port , which is greater than the power consumption of the device.
When you manually set the maximum power allocation, you must consider the power loss over the cable from the switch port to the powered device.
The cutoff power is the sum of the rated power consumption of the powered device and the worst-case power loss over the cable. The actual amount of power consumed by a powered device on a PoE port is the cutoff-power value plus a calibration factor of mW 0.
The actual cutoff value is approximate and varies from the configured value by a percentage of the configured value. For example, if the configured cutoff power is 12 W, the actual cutoff-value is We recommend that you enable power policing when PoE is enabled on your switch. For example, if policing is disabled and you set the cutoff-power value by using the power inline auto max interface configuration command, the configured maximum power allocation on the PoE port is 6.
The switch provides power to the connected devices on the port if the device needs up to 6. If the CDP-power negotiated value or the IEEE classification value exceeds the configured cutoff value, the switch does not provide power to the connected device. After the switch turns on power on the PoE port, the switch does not police the real-time power consumption of the device, and the device can consume more power than the maximum allocate d amount, which could adversely affect the switch and the devices connected to the other PoE ports.
The switch supports dual power supplies. If a power supply is removed or fails and the switch does not have enough power for the powered devices, the switch first denies power to low-priority ports in descending order of port numbers, and then to high priority ports in descending numbers. Each dual-purpose port is considered as a single interface with dual front ends an RJ connector and an SFP module connector.
The dual front ends are not redundant interfaces; the switch activates only one connector of the pair. The switch dynamically selects the dual-purpose port media type that first links up. However, you can use the media-type interface configuration command to manually select the RJ connector or the SFP module connector. The port LED is on for whichever connector is active. For more information about the LEDs, see the hardware installation guide. Devices within a single VLAN can communicate directly through any switch.
Ports in different VLANs cannot exchange data without going through a routing device. With a standard Layer 2 switch, ports in different VLANs have to exchange information through a router.
When the IP services image is running on the switch, routing can be enabled on the switch. Whenever possible, to maintain high performance, forwarding is done by the switch hardware.
The routing function can be enabled on all SVIs and routed ports. The switch routes only IP traffic. When IP routing protocol parameters and address configuration are added to an SVI or routed port, any IP traffic received from these ports is routed. Note To configure Layer 2 parameters, if the interface is in Layer 3 mode, you must enter the switchport interface configuration command without any parameters to put the interface into Layer 2 mode.
This shuts down the interface and then re-enables it, which might generate messages on the device to which the interface is connected.
When you put an interface that is in Layer 3 mode into Layer 2 mode, the previous configuration information related to the affected interface might be lost, and the interface is returned to its default configuration. When using the interface range global configuration command, note these guidelines:.
Note When you use the interface range command with port channels, the first and last port channel number must be active port channels. When using the define interface-range global configuration command, note these guidelines:. Note When you use the interface ranges with port channels, the first and last port channel number must be active port channels.
Speed and Duplex Configuration. When configuring an interface speed and duplex mode, note these guidelines:. Half-duplex mode is supported with the auto setting. Changing the interface type removes the speed and duplex configurations. The switch configures both media types to autonegotiate speed and duplex the default.
If you configure auto-select , you cannot configure the speed and duplex interface configuration commands. When you configure sfp or rj45 media type, the non-configured type is disabled, even if there is a connector installed in that interface and no connector in the configured one.
When the media type is auto-select , the switch uses these criteria to select the type:. Note An SFP is not installed until it has a fiber-optic or copper cable plugged in. You cannot set the MTU size for an individual interface. Layer 2 or switching mode switchport command. Flow control is set to receive : off.
It is always off for sent packets. Disabled on all Ethernet ports. Port blocking unknown multicast and unknown unicast traffic. Disabled not blocked only Layer 2 interfaces. Disabled only Layer 2 interfaces. Note The switch might not support a pre-standard powered device—such as Cisco IP phones and access points that do not fully support This is regardless of whether auto-MIDX is enabled on the switch port.
See the hardware installation guide for driver installation instructions. The connected device must include a terminal emulation application.
When the switch detects a valid USB connection to a powered-on device that supports host functionality such as a PC , input from the RJ console is immediately disabled, and input from the USB console is enabled. A LED on the switch shows which console connection is in use. The switch first displays the RJ media type.
In the sample output, the switch has a connected USB console cable. Because the bootloader did not change to the USB console, the first log from the switch shows the RJ console. A short time later, the console changes and the USB console log appears. You can configure the console type to always be RJ, and you can configure an inactivity timeout for the USB connector. Follow this procedure to select the RJ console media type.
Connect the switch to a PC or terminal through the RJ console port. For more information, see the hardware installation guide. Configure the console. Enter line configuration mode. Configure the console media type to always be RJ If you do not enter this command and both types are connected, the default is USB. Optional Save your entries in the configuration file. A log shows that this termination has occurred.
This example shows that the console on switch reverted to RJ A log entry shows when a console cable is attached. If a USB console cable is connected to the switch, it is prevented from providing input. This example reverses the previous configuration and immediately activates the USB console that is connected. The switch supports these interface types:. To configure a physical interface port , specify the interface type, the module number, and the switch port number, and enter interface configuration mode.
You can identify physical interfaces by physically checking the interface location on the switch. You can also use the show privileged EXEC commands to display information about a specific interface or all the interfaces on the switch.
The remainder of this document primarily provides physical interface configuration procedures. These general instructions apply to all interface configuration procedures. Step 2 Enter the interface global configuration command. Identify the interface type and the number of the connector. In this example, Fast Ethernet port 1 is selected:. Note You do not need to add a space between the interface type and interface number. Step 4 Follow each interface command with the interface configuration commands that the interface requires.
The commands that you enter define the protocols and applications that will run on the interface. The commands are collected and applied to the interface when you enter another interface command or enter end to return to privileged EXEC mode.
You can also configure a range of interfaces by using the interface range or interface range macro global configuration commands.
Interfaces configured in a range must be the same type and must be configured with the same feature options. Enter the show interfaces privileged EXEC command to see a list of all interfaces on or configured for the switch. A report is provided for each interface that the device supports or for the specified interface. You can use the interface range global configuration command to configure multiple interfaces with the same configuration parameters.
When you enter the interface range configuration mode, all command parameters that you enter are attributed to all interfaces within that range until you exit this mode.
Specify the range of interfaces VLANs or physical ports to be configured, and enter interface range configuration mode. Enable the port, if necessary. I can recommend it to anyone. Tim Flanigan. I am absolutely in love with this software!
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