WS-C3850-24P-S Cisco Catalyst Ethernet Switch

Product Outline

The Cisco WS-C3850-24P-S Catalyst is a high-performance managed Layer 3 switch designed for enterprise-grade networking environments. Built with advanced Gigabit Ethernet capabilities, this switch delivers reliable Power over Ethernet Plus (PoE+) connectivity, scalability, and intelligent traffic management for modern business networks.

General Specifications

Manufacturer & Model Details

• Brand: Cisco
• Model Number: WS-C3850-24P-S
• Product Type: Managed Layer 3 Ethernet Switch
• Form Factor: Desktop or Rack-Mountable (1U)
• Switch Subtype: Gigabit Ethernet

Port Configuration

• 24 x 10/100/1000 Mbps Ethernet ports
• Integrated Power over Ethernet Plus (PoE+)
• Total PoE power budget up to 435 Watts

Performance & Capacity

Switching & Stacking Performance

• Switching capacity up to 88 Gbps
• High-speed stacking bandwidth of 480 Gbps
• Cisco StackWise-480 technology for seamless scalability

Routing & Network Capacity

• Supports up to 24,000 IPv4 routes
• Handles 24,000 Flexible NetFlow entries
• Up to 1,000 Switched Virtual Interfaces (SVIs)
• MAC address table capacity of 32,000 entries
• Jumbo frame support up to 9,198 bytes

Advanced Networking Features

Routing & Management Protocols

• Routing protocols: RIP v1, RIP v2, EIGRP, RIPng
• Remote management: SNMP v1/v2c/v3, SSH, Telnet, CLI, RMON 1 & 2

Layer 2 & Layer 3 Capabilities

• VLAN tagging and trunking support
• Rapid Spanning Tree (RSTP) and Multiple Spanning Tree (MSTP)
• Per-VLAN Rapid Spanning Tree Plus (PVRST+)
• Layer 3 load balancing and VRF-Lite

Security & Traffic Control

• Access Control Lists (ACLs) for enhanced security
• DHCP snooping and Dynamic ARP Inspection (DAI)
• 802.1X authentication and RADIUS support
• IGMP and MLD snooping for multicast optimization

Energy Efficiency & Reliability

Power & Redundancy

• AC input: 120/230V at 50–60 Hz
• Optional power supply redundancy
• Energy Efficient Ethernet for reduced power consumption
• Cisco StackPower technology for power sharing

Standards & Compliance

Supported IEEE Standards

• IEEE 802.3, 802.3u, 802.3ab, 802.3z
• IEEE 802.1Q, 802.1D, 802.1P, 802.1W, 802.1S
• IEEE 802.3af and 802.3at for PoE and PoE+
• IEEE 802.3ad (LACP) and 802.1X

Cisco Catalyst 3850 Series

The Cisco WS-C3850-24P-S is a cornerstone model within the innovative Catalyst 3850 Series, a family of switches that revolutionized enterprise networking by introducing the concept of Converged Access. This architectural breakthrough integrates wired switching, wireless LAN controller functionality, and advanced application visibility into a single, programmable device. Designed for the borderless network, the 3850 Series delivers exceptional performance, scalability, and operational simplicity, making it an ideal choice for demanding campus environments, from access layer deployments to compact core and aggregation layer implementations.

Deep Dive: The WS-C3850-24P-S Model Specifications

This specific SKU, the WS-C3850-24P-S, is a fully-configured, stackable, Layer 3 switch designed for high-performance access. The "24P" denotes 24 Ethernet ports capable of delivering IEEE 802.3at PoE+ (Power over Ethernet Plus) power, while the "-S" suffix indicates it includes IP Services feature set software for advanced routing capabilities. It is a fixed-configuration switch that forms the intelligent edge of the network, connecting everything from IP phones and wireless access points to surveillance cameras and workstations.

Hardware Architecture & Performance

At its core, the Catalyst 3850 utilizes a Unified Access Data Plane (UADP) application-specific integrated circuit (ASIC). This custom silicon is the engine behind its converged capabilities, enabling consistent feature implementation and policy application across both wired and wireless clients. The switch offers 480 Gbps of stacking bandwidth through its built-in StackWise-480 ports, allowing multiple physical switches to operate as a single, logical entity. With a forwarding rate of up to 176 Mpps (million packets per second) for the stack, it ensures wire-speed performance even under heavy, multi-service loads.

Port Configuration Details

24 x 10/100/1000BASE-T Ports: All 24 RJ-45 copper ports are autosensing and support Gigabit Ethernet. Critically, each port is capable of delivering up to 30 watts of power per port (PoE+) to connected devices.
4 x 1G SFP Uplinks: Dedicated Gigabit Ethernet Small Form-Factor Pluggable (SFP) ports for fiber or copper uplinks, providing flexibility in connecting to distribution or core layers.
StackWise-480 Ports: Specialized ports for creating a high-speed, redundant backplane stack with other Catalyst 3850 switches.

Power & Cooling Specifications

The switch is designed with a robust internal power supply. Its total PoE budget is a substantial 440 watts, allowing it to power a dense deployment of PoE+ devices like Cisco Aironet 3700 or 2800 Series Access Points simultaneously. The fan design is optimized for front-to-back airflow, making it suitable for deployment in standard rack environments with hot-aisle/cold-aisle configurations.

Key Technologies and Feature Sets

The value of the Cisco WS-C3850-24P-S extends far beyond its hardware. It is defined by a suite of embedded technologies that simplify operations, enhance security, and optimize application performance.

Cisco StackWise-480 Technology

StackWise-480 is a deterministic, cross-bar switching architecture that creates a single, unified switching plane from up to nine individual Catalyst 3850 switches. This stacking technology provides:

Single Point of Management: The entire stack is managed as one device through one IP address, drastically reducing administrative overhead.
High Resiliency: Hitless failover and stateful switchover ensure that if the stack master fails, a backup member assumes control with minimal disruption.
Scalable Bandwidth: The full 480 Gbps of stacking bandwidth is available for inter-unit traffic, ensuring performance scales with the stack size.

Integrated Wireless LAN Controller Functionality

This is the defining feature of the Converged Access architecture. Each Catalyst 3850 switch can natively control up to 50 Cisco Aironet access points (with licenses), eliminating the need for a separate physical wireless LAN controller.

Unified Policy: Apply consistent quality of service (QoS), security (ACLs), and application policies to users regardless of whether they connect via wire or Wi-Fi.
Seamless Mobility: Clients can roam between access points controlled by the same or different 3850 switches in a stack or connected via FlexConnect, with persistent application experience.
Reduced TCO: Consolidation of wired and wireless control reduces hardware, power, cooling, and management costs.

Advanced Routing with IP Services

The "IP Services" software image unlocks full Layer 3 dynamic routing capabilities, transforming the switch from a simple access device into a potent routing platform. Key protocols include:

Dynamic Routing: Full support for OSPF, EIGRP, BGPv4, and IS-IS for scalable interior and exterior gateway routing.
IPv6 Support: Comprehensive dual-stack (IPv4/IPv6) deployment capabilities, including routing protocols like OSPFv3 and EIGRP for IPv6.
Enhanced Services: Support for Policy-Based Routing (PBR), Multiprotocol Label Switching (MPLS), and advanced multicast protocols (PIM-SM, PIM-SSM).

Software-Defined Access & Programmability

The Catalyst 3850 platform is a foundational element for Cisco's Software-Defined Access (SD-Access) solution, providing the network fabric for intent-based networking.

Cisco DNA Center Ready

The switch is fully compatible with Cisco DNA Center, a centralized management dashboard. This enables:

Automated Provisioning: Zero-touch deployment and Day 0/1 configuration through templated policies.
Assurance & Analytics: AI/ML-driven insights into network health, client experience, and application performance, providing proactive issue resolution.
Fabric Enablement: Acts as a fabric border, edge, or intermediate node within an SD-Access overlay network, enabling scalable segmentation and policy enforcement.

Open Programmability with APIs

Moving beyond traditional CLI, the 3850 supports modern programmatic interfaces:

REST APIs: Northbound RESTful APIs for integration with custom applications and orchestration tools.
Python Scripting: On-box Python interpreter for running custom scripts to automate operational tasks and gather data.
Model-Driven Programmability: Support for YANG data models and NETCONF/RESTCONF protocols for standardized, model-driven network management.

Security and Network Management

Enterprise-grade security is built into every layer of the switch's operation, protecting infrastructure, data, and access.

Comprehensive Security Feature Suite

TrustSec Technology: Implements scalable Group-Based Policy (SGT) for segmentation, encrypting metadata to enforce policies regardless of IP address.
Advanced Threat Protection: Integration with Cisco's Identity Services Engine (ISE) for context-aware network access control (802.1X, MAB, WebAuth).
Device Hardening: Features like Control Plane Policing (CoPP), DHCP snooping, Dynamic ARP Inspection (DAI), and IP Source Guard protect the switch's management plane and network integrity.
Encrypted Traffic Analytics (ETA): A breakthrough capability that uses machine learning to detect threats in encrypted traffic without decrypting it, identifying malware communications patterns.

Management & Visibility Tools

Beyond DNA Center, the switch offers multiple management avenues:

Cisco Prime Infrastructure: For traditional lifecycle management of both wired and wireless networks.
Cisco Command-Line Interface (CLI): The industry-standard, robust CLI for detailed configuration and troubleshooting.
Embedded Event Manager (EEM): A powerful tool to create custom event-driven policies that automate responses to specific network conditions.
Flexible NetFlow: Provides detailed visibility into network traffic patterns, supporting application recognition.

Deployment Scenarios & Use Cases

The versatility of the Cisco WS-C3850-24P-S makes it suitable for a wide array of deployment scenarios in mid-to-large-sized enterprises, education, healthcare, and government.

Ideal Deployment Environments

Campus Access Layer: The primary use case, providing high-density PoE+ for VoIP phones, wireless APs, and user workstations in office floors, classrooms, or hospital wards.
Branch Office Aggregation: Serving as a compact, do-it-all switch for branch offices, combining user access, wireless control, and WAN routing in a single device.
Mid-Sized Network Core: In smaller campus networks, a stack of Catalyst 3850 switches can provide the routing and switching core with high availability and advanced features.
High-Density Wireless Deployment: Perfect for environments with intensive Wi-Fi needs, such as lecture halls or open-plan offices, where its integrated WLAN controller and ample PoE budget are critical.

Comparison with Related Catalyst Models

Understanding where the WS-C3850-24P-S fits within the broader Catalyst portfolio is key.

vs. Catalyst 2960-X: The 2960-X is a Layer 2 access switch. The 3850 adds full Layer 3 routing, StackWise-480, and the integrated wireless controller.
vs. Catalyst 3650: The Catalyst 3650 is closely related but offers StackWise-160 and a different feature set. The 3850 provides higher stacking bandwidth and is the lead platform for SD-Access.
vs. Catalyst 9300: The Catalyst 9300 is the next-generation successor, based on the Cisco UADP 3.0 ASIC, offering higher port density, multi-gigabit Ethernet (mGig), and enhanced programmability. The 3850 represents a mature, field-proven platform.