Chapter 3 Troubleshooting

Diagnosing Problems

Ping End Device

Ping 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 identify the end device MAC address in its Content-Addressable Memory (CAM) table.

Spanning Tree Loops

STP loops can cause serious performance issues that look like port or interface problems.

A unidirectional link can cause loops. It occurs when 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 problems, or a port issue could cause this one-way communication.

You can enable UniDirectional Link Detection (UDLD) on the switch to help identify unidirectional link problems. For information about enabling UDLD on the switch, see the “Understanding UDLD” section in the switch software configuration guide on Cisco.com.

Switch Performance

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 mean a speed or duplex mismatch.

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

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

•Let both ports autonegotiate both speed and duplex.

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

•If a remote device does not autonegotiate, use the same duplex settings on the two ports. The speed parameter adjusts itself even if the connected port does not autonegotiate.

Autonegotiation and Network Interface Cards

Problems sometimes occur between the switch and third-party network interface cards (NICs). By default, the switch ports and interfaces autonegotiate. Laptops or other devices are commonly set to autonegotiate, yet sometimes autonegotiation issues occur.

To troubleshoot autonegotiation problems, try manually setting both sides of the connection. If this does not solve the problem, there could be a problem with the firmware or software on your NIC. You can resolve this by upgrading the NIC driver to the latest version.

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Cisco Systems WSC2960S24TSSRF Switch Performance, Ping End Device, Spanning Tree Loops, Speed, Duplex, and Autonegotiation
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2960S, WSC2960S24TSSRF, 2960S-24TS-S, 2960 specifications

Cisco Systems 2960 series switches are a prominent solution in the networking landscape, known for their reliability, scalability, and feature-rich offerings. Ideal for small to medium-sized enterprises, these switches provide a robust foundation for network infrastructure, ensuring optimal performance and connectivity.

One of the standout features of the Cisco 2960 series is its Layer 2 switching capabilities. The switches support multiple VLANs (Virtual Local Area Networks), allowing network administrators to segment traffic efficiently and enhance security protocols. This is crucial in modern networks where managing traffic and isolating sensitive information is a priority.

The Cisco 2960 series also incorporates advanced Quality of Service (QoS) features, enabling the prioritization of critical applications and services. This functionality ensures that time-sensitive data, such as voice and video traffic, maintains a high quality of service even in congested networks. With support for IEEE 802.1p and DSCP marking, administrators can fine-tune their network performance to meet specific organizational needs.

Power over Ethernet (PoE) is another significant characteristic of the Cisco 2960 series. This feature allows switches to deliver electrical power alongside data over Ethernet cables to devices such as IP phones, wireless access points, and surveillance cameras. With PoE, organizations can reduce clutter from power cables and increase deployment flexibility for various devices.

In terms of security, the Cisco 2960 series is equipped with a range of integrated security features. The switch supports port security, 802.1X authentication, and Access Control Lists (ACLs), providing robust defenses against unauthorized access and potential network vulnerabilities. These security measures are essential for protecting sensitive data and ensuring compliance with industry regulations.

Moreover, the Cisco 2960 series offers enhanced network management capabilities with Cisco's Intelligent Network Services. This includes support for Simple Network Management Protocol (SNMP), Cisco Prime, and Embedded Event Manager (EEM), allowing for efficient monitoring, troubleshooting, and policy enforcement across the network.

Additionally, the Cisco 2960 switches provide various models and configurations, catering to different networking needs. Options include models with varying port densities, uplink configurations, and stacking capabilities, making it easy for organizations to choose solutions that align perfectly with their requirements.

In summary, the Cisco 2960 series is a versatile and essential component of modern networking environments. Its advanced features, including Layer 2 support, QoS, PoE, robust security, and diverse management tools, make it an excellent choice for organizations looking to build a strong and secure network infrastructure.
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