Cisco Catalyst 9300 Switches: Руководство по устранению неполадок программного обеспечения PDF

Lost or Forgotten Password on a Device

Troubleshooting the Software Configuration This chapter describes how to identify and resolve software problems related to the Cisco IOS software on the switch. Depending on the nature of the problem, you can use the command-line interface (CLI), Device Manager, or Network Assistant to identify and solve problems. Additional troubleshooting information, such as LED descriptions, is provided in the hardware installation guide.

Information About Troubleshooting the Software Configuration, on page 1 How to Troubleshoot the Software Configuration, on page 10 Verifying Troubleshooting of the Software Configuration, on page 22 Scenarios for Troubleshooting the Software Configuration, on page 25 Configuration Examples for Troubleshooting Software, on page 27 Additional References for Troubleshooting Software Configuration, on page 29 Feature History for Troubleshooting Software Configuration, on page 29 Information About Troubleshooting the Software Configuration Software Failure on a Switch Switch software can be corrupted during an upgrade by downloading the incorrect file to the switch, and by deleting the image file.

In all of these cases, the switch does not pass the power-on self-test (POST), and there is no connectivity. Follow the steps described in the Recovering from a Software Failure, on page 10 section to recover from a software failure. Lost or Forgotten Password on a Device The default configuration for the device allows an end user with physical access to the device to recover from a lost password by interrupting the boot process during power-on and by entering a new password. These recovery procedures require that you have physical access to the device. Troubleshooting the Software Configuration 1

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Disabled Port Caused by Power Loss

Note On these devices, a system administrator can disable some of the functionality of this feature by allowing an end user to reset a password only by agreeing to return to the default configuration. If you are an end user trying to reset a password when password recovery has been disabled, a status message reminds you to return to the default configuration during the recovery process. You cannot recover encryption password key, when Cisco WLC configuration is copied from one Cisco WLC to another (in case of an RMA). Note Follow the steps described in the section Recovering from a Lost or Forgotten Password, on page 14 to recover from a lost or forgotten password.

Power over Ethernet Ports A Power over Ethernet (PoE) switch port automatically supplies power to one of these connected devices if the switch detects that there is no power on the circuit: • a Cisco pre-standard powered device (such as a Cisco IP Phone or a Cisco Aironet Access Point) • an IEEE 802.3af-compliant powered device • an IEEE 802.3at-compliant powered device A powered device can receive redundant power when it is connected to a PoE switch port and to an AC power source. The device does not receive redundant power when it is only connected to the PoE port.

After the switch detects a powered device, the switch determines the device power requirements and then grants or denies power to the device. The switch can also detect the real-time power consumption of the device by monitoring and policing the power usage. For more information, see the "Configuring PoE" chapter in the Interface and Hardware Component Configuration Guide (Catalyst 9300 Switches) . Refere the section Scenarios to Troubleshoot Power over Ethernet (PoE), on page 25 for various PoE troubleshooting scenarios.

Disabled Port Caused by Power Loss If a powered device (such as a Cisco IP Phone 7910) that is connected to a PoE device port and powered by an AC power source loses power from the AC power source, the device might enter an error-disabled state. To recover from an error-disabled state, enter the shutdown interface configuration command, and then enter the no shutdown interface command. You can also configure automatic recovery on the device to recover from the error-disabled state.

On a device, the errdisable recovery cause loopback and the errdisable recovery interval seconds global configuration commands automatically take the interface out of the error-disabled state after the specified period of time. Troubleshooting the Software Configuration Power over Ethernet Ports Troubleshooting the Software Configuration 2

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Layer 2 Traceroute Guidelines

Disabled Port Caused by False Link-Up If a Cisco powered device is connected to a port and you configure the port by using the power inline never interface configuration command, a false link-up can occur, placing the port into an error-disabled state. To take the port out of the error-disabled state, enter the shutdown and the no shutdown interface configuration commands. You should not connect a Cisco powered device to a port that has been configured with the power inline never command. Ping The device supports IP ping, which you can use to test connectivity to remote hosts. Ping sends an echo request packet to an address and waits for a reply. Ping returns one of these responses:

• Normal response—The normal response ( hostname is alive) occurs in 1 to 10 seconds, depending on network traffic. • Destination does not respond—If the host does not respond, a no-answer message is returned. • Unknown host—If the host does not exist, an unknown host message is returned. • Destination unreachable—If the default gateway cannot reach the specified network, a destination-unreachable message is returned. • Network or host unreachable—If there is no entry in the route table for the host or network, a network or host unreachable message is returned. Refere the section Executing Ping, on page 20 to understand how ping works.

Layer 2 Traceroute The Layer 2 traceroute feature allows the switch to identify the physical path that a packet takes from a source device to a destination device. Layer 2 traceroute supports only unicast source and destination MAC addresses. Traceroute finds the path by using the MAC address tables of the devices in the path. When the Device detects a device in the path that does not support Layer 2 traceroute, the Device continues to send Layer 2 trace queries and lets them time out. The Device can only identify the path from the source device to the destination device.

It cannot identify the path that a packet takes from source host to the source device or from the destination device to the destination host. Layer 2 Traceroute Guidelines • Cisco Discovery Protocol (CDP) must be enabled on all the devices in the network. For Layer 2 traceroute to function properly, do not disable CDP. If any devices in the physical path are transparent to CDP, the switch cannot identify the path through these devices. • A device is reachable from another device when you can test connectivity by using the ping privileged EXEC command. All devices in the physical path must be reachable from each other. • The maximum number of hops identified in the path is ten.

Troubleshooting the Software Configuration Disabled Port Caused by False Link-Up Troubleshooting the Software Configuration 3

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IP Traceroute

• You can enter the traceroute mac or the traceroute mac ip privileged EXEC command on a device that is not in the physical path from the source device to the destination device. All devices in the path must be reachable from this switch. • The traceroute mac command output shows the Layer 2 path only when the specified source and destination MAC addresses belong to the same VLAN. If you specify source and destination MAC addresses that belong to different VLANs, the Layer 2 path is not identified, and an error message appears. • If you specify a multicast source or destination MAC address, the path is not identified, and an error message appears.

• If the source or destination MAC address belongs to multiple VLANs, you must specify the VLAN to which both the source and destination MAC addresses belong. If the VLAN is not specified, the path is not identified, and an error message appears. • The traceroute mac ip command output shows the Layer 2 path when the specified source and destination IP addresses belong to the same subnet. When you specify the IP addresses, the device uses the Address Resolution Protocol (ARP) to associate the IP addresses with the corresponding MAC addresses and the VLAN IDs. • If an ARP entry exists for the specified IP address, the device uses the associated MAC address and identifies the physical path.

• If an ARP entry does not exist, the device sends an ARP query and tries to resolve the IP address. If the IP address is not resolved, the path is not identified, and an error message appears. • When multiple devices are attached to one port through hubs (for example, multiple CDP neighbors are detected on a port), the Layer 2 traceroute feature is not supported. When more than one CDP neighbor is detected on a port, the Layer 2 path is not identified, and an error message appears. • This feature is not supported in Token Ring VLANs.

• Layer 2 traceroute opens a listening socket on the User Datagram Protocol (UDP) port 2228 that can be accessed remotely with any IPv4 address, and does not require any authentication. This UDP socket allows to read VLAN information, links, presence of particular MAC addresses, and CDP neighbor information, from the device. This information can be used to eventually build a complete picture of the Layer 2 network topology. • Layer 2 traceroute is disabled by default and can be enabled by running the l2 traceroute command in global configuration mode.

To disable Layer 2 traceroute, use the no l2 traceroute command in global configuration mode IP Traceroute You can use IP traceroute to identify the path that packets take through the network on a hop-by-hop basis. The command output displays all network layer (Layer 3) devices, such as routers, that the traffic passes through on the way to the destination. Your Device can participate as the source or destination of the traceroute privileged EXEC command and might or might not appear as a hop in the traceroute command output. If the Device is the destination of the traceroute, it is displayed as the final destination in the traceroute output.

Intermediate devices do not show up in the traceroute output if they are only bridging the packet from one port to another within the same VLAN. However, if the intermediate Device is a multilayer Device that is routing a particular packet, this device shows up as a hop in the traceroute output. Troubleshooting the Software Configuration IP Traceroute Troubleshooting the Software Configuration 4

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