Cisco Systems 3560-E, 3750-E manual Check Switch Performance, Ping End Device, Spanning Tree Loops

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Chapter 4 Troubleshooting

Diagnosing Problems

port. Use the show interfaces privileged EXEC command to check the port or interface error-disabled, disabled, or shutdown status on both sides of the connection. If needed, re-enable the port or the interface.

Ping End Device

Check the end device by pinging from the directly connected switch first, and then work your way back port by port, interface by interface, trunk by trunk, until you find the source of the connectivity issue. Make sure that each switch can see the end device MAC address in its Content-Addressable Memory (CAM) table.

Spanning Tree Loops

Spanning Tree Protocol (STP) loops can cause serious performance issues that look like port or interface problems. In this situation, the switch bandwidth is used over and over again by the same frames, leaving little room for legitimate traffic.

Loops can be caused by a unidirectional link. A unidirectional link occurs whenever the traffic sent by the switch is received by its neighbor, but the traffic from the neighbor is not received by the switch. A broken fiber-optic cable, other cabling, or a port issue could cause this one-way communication.

You can enable UniDirectional Link Detection (UDLD) on the switch to help identify difficult-to-find unidirectional link problems. UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD detects unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive mode, UDLD also detects unidirectional links due to one-way traffic on fiber-optic and twisted-pair links and due to misconnected interfaces on fiber-optic links. For information about enabling UDLD on the switch, see the “Understanding UDLD” section in the software configuration guide for this release.

Check Switch Performance

Review this section when troubleshooting switch performance problems.

Speed, Duplex, and Autonegotiation

If the port statistics show a large amount of alignment errors, frame check sequence (FCS), or late-collisions errors, this might indicate a speed or duplex mismatch.

A common issue with speed and duplex is when the duplex settings are mismatched between two switches, between a switch and a router, or between the switch and a workstation or server. This can happen when manually setting the speed and duplex, or from autonegotiation issues between the two devices. A mismatch occurs under these circumstances:

•A manually set speed or duplex parameter is different from the manually set speed or duplex parameter on the connected port.

•A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.

To maximize switch performance and ensure a link, follow one of these guidelines when changing the settings for duplex and speed:

•Let both ports autonegotiate both speed and duplex.

•Manually set the speed and duplex parameters for the ports on both ends of the connection.

Catalyst 3750-E and Catalyst 3560-E Switch Hardware Installation Guide

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Contents Americas Headquarters Text Part Number OL-9774-03Page N T E N T S Connecting Devices to the Ethernet Ports Wiring the DC-Input Power Source Accessing the CLI Through the Console Port C-1 Purpose AudienceConventions Related Publications ViiiPreface OL-9774-03 Switch Models Part Number DescriptionSwitch Part Number Description Front Panel Description24- and 48-Port Switch Front Panel 10/100/1000 Ethernet Ports PoE PortsSFP Modules Gigabit Ethernet Module SlotsCisco TwinGig Converter Module 24- and 48-Port Switch LEDs LEDsSystem LED Color System StatusPower Supply LEDs Master LEDColor RPS Status ColorFan LED Mode LED Port Mode DescriptionPort LEDs and Modes Port Mode Port LED Color Meaning PoE LED Color PoE StatusStack LED Stack LED24- and 48-Port Switch Rear Panel Rear Panel DescriptionCatalyst 3560E-12D Switch Rear Panel StackWise PortsPower-Supply Modules 48-Port Switch Power-Supply ModulesSwitch Port PoE Port non-PoE Port Non-PoEAC-Power-Supply Module LEDs DC-Power-Supply Module LEDs DescriptionFan Modules Module LEDs DescriptionRPS Connector Management PortsManagement Options Network Configurations Preparing for Installation Safety WarningsOL-9774-03 Switch Installation Preparing for Installation Statement 371-Power Cable and AC Adapter Box Contents Installation GuidelinesTools and Equipment Planning a Switch Stack Catalyst 3750-E Switches Switch Stacking GuidelinesStack Cabling Configurations Stack Bandwidth and Partitioning Examples Example of a Stack with Full Bandwidth ConnectionsPower On Sequence for Switch Stacks Example of a Stack with a Failover ConditionInstalling the Switch Rack-MountingRack-Mounting Brackets 10 Removing Screws from the Switch Attaching the Rack-Mount Brackets11 Attaching Brackets for 19-inch Racks Mounting the Switch in a Rack Mounting the Switch in a RackAttaching the Brackets to the Switch for Wall-Mounting Wall-MountingMounting the Catalyst 3560E-12D Switch on a Wall Mounting the Catalyst 3560E-12SD Switch on a Wall After Installing the Switch Table- or Shelf-MountingConnecting to the StackWise Ports Catalyst 3750-E Switches Installing Devices in the 10-Gigabit Ethernet Slots Installing X2 Transceiver Modules and Converter ModulesModule inserted face up Module inserted face down 202046 Installing SFP Modules Removing an X2 Transceiver Module or Converter ModuleInstalling an SFP Module Lower SFP modules are inverted on 24- and 48-port switches Connecting Devices to the Ethernet Ports Removing an SFP ModulePoE Port Connections 10/100/1000 Ethernet Port ConnectionsDevice Crossover Cable Switch Installation Connecting Devices to the Ethernet Ports Where to Go Next OL-9774-03 Power Supply and Fan Module Installation Installation OverviewOL-9774-03 Installing an AC-Power Supply Inserting the AC-Power Supply in 24- and 48-Port SwitchesInstalling a DC-Power Supply AC-Power Supply with Power Cord RetainerPreparing for Installation Grounding the SwitchStripping the Ground Wire See -9for the Catalyst 3560E-12SD ground location Installing the DC Power Supply in the Switch Inserting the DC-Power Supply in 24- and 48-Port SwitchesWiring the DC-Input Power Source Installing a Fan Module 12 Inserting the Fan Module in 24- and 48-Port Switches202049 OL-9774-03 Diagnosing Problems Check Switch Post ResultsCheck Switch LEDs Check Switch ConnectionsBad or Damaged Cable Ethernet and Fiber CablesPort and Interface Settings Transceiver IssuesPoE Connections Check Switch Performance Ping End DeviceSpanning Tree Loops Speed, Duplex, and AutonegotiationAutonegotiation and NIC Cards How to Clear the Switch IP Address and ConfigurationCabling Distance Finding the Switch Serial Number How to Replace a Failed Stack MemberTroubleshooting How to Replace a Failed Stack Member OL-9774-03 Physical Specifications Environmental RangesPower Specifications Table A-5 OL-9774-03 Connector and Cable Specifications Connector Specifications10/100/1000 Ports Gigabit Ethernet Module InterfacesFigure B-4 Duplex LC Cable Connector 10/100 Ethernet Management Port Console PortCable and Adapter Specifications Gigabit Ethernet X2 Transceiver Module Cable SpecificationsModal X2 Product Wavelength Core Size Bandwidth Number Microns MHz/kmSFP Module Cable Specifications X2 Product Transmit Power Receive Power NumberTransmit DBm Wavelength nmFour Twisted-Pair Cable Pinouts 652 43.4 to 62 miles 1530 To 100 km 1570 1610Two Twisted-Pair Crossover Cable Schematic Two Twisted-Pair Cable PinoutsSwitch Console RJ-45-to-DB-9 Port DTE Identifying a Crossover CableConsole Port Adapter Pinouts DeviceSwitch Console RJ-45-to-DB-25 Port DTE Accessing the CLI Through Express Setup Accessing the CLIAccessing the CLI Through the Console Port IP Settings Entering the Initial Configuration InformationConnecting to the Console Port Completing the Setup Program Line vty 0 These choices appear OL-9774-03 Numerics IN-2 IN-3 IN-4 IN-5 IN-6
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