WS-C2948G-L3 Cisco Ethernet Switch (48 Ports)

In-Depth Technical Specifications & Architecture

A thorough understanding of the WS-C2948G-L3's specifications is crucial for determining its suitability for specific network requirements, even in a legacy context.

Core Hardware Architecture

The switch is built on a purpose-built switching fabric and a dedicated route processor, designed to handle traffic for all ports simultaneously without blocking.

Switching Fabric & Performance

Backplane Bandwidth: 48 Gbps, supporting non-blocking, wire-speed performance on all ports.
Forwarding Rate: Up to 36 million packets per second (Mpps).
Packet Buffer Memory: 4 MB shared memory architecture for efficient congestion management.

Port Configuration & Interfaces

Fixed Ethernet Ports: 48 x 10/100/1000BASE-T Gigabit Ethernet RJ-45 ports with auto-negotiation and auto-MDIX.
Expansion Slots: 2 dedicated Gigabit Interface Converter (GBIC) slots for uplink flexibility.

GBIC Slot Compatibility & Use Cases

The two open GBIC slots are a critical subcategory. They allow network architects to tailor uplink connectivity using various standardized GBIC modules:

Cisco GLC-LH-SM: 1000BASE-LX/LH GBIC for long-range single-mode fiber connections (up to 10 km).
Cisco GLC-SX-MM: 1000BASE-SX GBIC for multi-mode fiber connections (up to 550 m).
Cisco GLC-T: 1000BASE-T GBIC for copper uplinks over RJ-45.
These slots enable high-speed trunking to core switches, long-distance building-to-building links, or connectivity to dedicated storage or server farms.

Layer 3 Routing Capabilities

This is the defining feature of the 2948G-L3. Its routing subsystem supports:

Routing Protocols: Full support for RIPv1/v2, OSPF, EIGRP, and BGPv4 for enterprise interior and exterior routing.
IP Routing Entries: Capable of holding up to 32,000 routes in hardware.
Unicast & Multicast Routing: Supports Protocol Independent Multicast (PIM) for efficient multicast traffic handling.

Modern Applications & Key Use Cases

While no longer for frontline enterprise deployment, the WS-C2948G-L3 excels in several specific scenarios.

Dedicated Lab and Testing Environments

Ideal for CCIE/CCNP lab preparation, software development testing, and network design prototyping, offering real hardware experience at low cost.

Industrial & Embedded Deployments

Its rugged design and lack of moving parts (fanless options exist) make it suitable for manufacturing floors, utility SCADA networks, and other harsh environments where absolute reliability is valued over the latest speed.

Legacy Application

Provides connectivity for older machinery, proprietary systems, or server hardware that requires a stable, unchanging network environment without the complexity of a modern software-defined network.

Cost-Effective Network Segmentation

Can act as a dedicated aggregation switch for a department or a small branch, providing VLAN segmentation and inter-VLAN routing, isolating broadcast domains and enforcing security policies between subnets.

Power Supply Units (PSUs) and Redundancy

The switch supports different PSU models. A key subcategory is the redundant power supply (RPS) system. The Cisco RPS 675 provides backup power for multiple Cisco devices, including the 2948G-L3, and is a crucial accessory for mission-critical deployments.

Fan Tray Operation and Replacements

Cooling is vital. Most models have a field-replaceable fan tray. Ensuring it is operational or sourcing a replacement is a common requirement in the secondary market.

Memory Upgrades & Firmware

Flash Memory & DRAM Considerations

The switch uses standard, upgradeable DIMMs and CompactFlash for the IOS image. Upgrading to the maximum 256 MB DRAM and 32 MB Flash can enable support for more advanced features and larger routing tables.

IOS Software Version Selection

This is a major subcategory. Different IOS feature sets are available (e.g., IP Base, IP Services). Sourcing the correct, licensed IOS image with the required feature set (Layer 3 routing, advanced security) is paramount.