WS-C3850-24P-S Cisco 24-Port Switch

Advanced Managed Network Switch Overview

The Cisco WS-C3850-24P-S Catalyst is a high-performance Layer 3 managed switch designed for enterprise-grade networking. It delivers reliable Gigabit Ethernet connectivity, advanced routing, and intelligent power management, making it ideal for modern business networks, campuses, and data-driven environments.

General Product Details

• Brand: Cisco
• Model Number: WS-C3850-24P-S
• Device Category: Managed Layer 3 Ethernet Switch
• Port Density: 24 Gigabit Ethernet Ports
• Form Factor: Desktop or 1U Rack-Mountable
• Stackable Design: Yes
• Network Technology: Gigabit Ethernet

PoE+ Capabilities and Power Efficiency

This Cisco Catalyst switch supports Power over Ethernet Plus (PoE+), enabling it to power IP phones, wireless access points, and surveillance cameras directly through Ethernet cables.

• PoE Standard: PoE+
• Total PoE Budget: 435 Watts
• Power Input: AC 120V / 230V (50–60 Hz)
• Redundant Power Support: Optional

Switching Performance and Scalability

Engineered for demanding workloads, this managed switch ensures fast data forwarding, seamless stacking, and scalable network expansion.

• Switching Capacity: 88 Gbps
• Stacking Bandwidth: 480 Gbps
• MAC Address Table: Supports up to 32,000 entries
• Jumbo Frame Size: Up to 9,198 bytes

Routing and Network Capacity

• IPv4 Routing Entries: Up to 24,000
• NetFlow Records: 24,000 entries
• Switched Virtual Interfaces (SVIs): Up to 1,000

Supported Routing Protocols

The switch offers robust Layer 3 routing with support for both IPv4 and IPv6 protocols, ensuring flexible network design.

• RIP v1 and RIP v2
• EIGRP
• RIPng

Remote Management

Simplify administration with extensive remote management options and secure access methods.

• SNMP v1, v2c, and v3
• RMON 1 and 2
• SSH and Telnet
• Command Line Interface (CLI)

Enterprise-Class Network Features

Designed for reliability and control, this Cisco managed switch includes a comprehensive set of enterprise networking features.

• VLAN and trunking support
• Auto-negotiation and Auto MDI/MDI-X
• IGMP and MLD Snooping
• Quality of Service (QoS)
• Access Control Lists (ACL)
• DHCP Snooping and Dynamic ARP Inspection
• IPv4 and IPv6 compatibility
• Energy Efficient Ethernet

Spanning Tree and Link Management Technologies

• Rapid Spanning Tree Protocol (RSTP)
• Multiple Spanning Tree Protocol (MSTP)
• Per-VLAN Rapid Spanning Tree Plus (PVRST+)
• STP Root Guard and UDLD
• LACP and PAgP Link Aggregation

Cisco Exclusive Technologies

This switch integrates proprietary Cisco innovations to enhance network performance, resilience, and visibility.

• Cisco StackWise-480 Technology
• Cisco StackPower Technology
• Flexible NetFlow (FNF)
• Remote SPAN (RSPAN)
• Layer 3 Load Balancing

Industry Standards and Compliance

The Cisco WS-C3850-24P-S complies with a wide range of IEEE standards to ensure compatibility and interoperability.

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

Cisco Catalyst 3850 Series: The Converged Access

The Cisco Catalyst 3850 Series represents a paradigm shift in enterprise networking, introducing the groundbreaking Converged Access architecture. This category of switches, exemplified by the WS-C3850-24P-S model, is engineered to unify wired and wireless network services onto a single, resilient platform. By integrating a Wireless LAN Controller (WLC) directly into the switch's operating system (IOS XE), the Catalyst 3850 eliminates the need for separate overlay networks, simplifying management, enhancing visibility, and dramatically improving operational efficiency. These switches are designed for the access layer of demanding enterprise environments, such as corporate campuses, large branch offices, and education institutions, where scalability, security, and seamless user experience are non-negotiable. The "PoE+" designation in models like the 24P-S underscores its capability to deliver both data and up to 30 watts of power per port to a vast array of devices, from VoIP phones and wireless access points to advanced building management systems.

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

The Cisco WS-C3850-24P-S is a specific, fixed-configuration member of the 3850 family, designed to deliver robust Layer 3 switching with comprehensive Power over Ethernet Plus (PoE+) support. Its hardware configuration is meticulously crafted for high-performance access deployments.

Core Hardware Architecture

At its heart, the WS-C3850-24P-S is built on a powerful multi-core CPU architecture that runs Cisco's IOS XE operating system. This provides the computational foundation for unified wired-wireless control, advanced security features, and application visibility. The switch features a high-performance switching fabric that ensures low-latency, line-rate forwarding across all ports, even under full load. Its stackable design, using Cisco StackWise-480 technology, is a critical component, allowing multiple physical switches to operate as a single, logical entity with a unified management plane and control plane.

Port Configuration and Stacking Details

The "24P" in the model number signifies 24 Ethernet ports, all of which are capable of IEEE 802.3at PoE+ delivery. These ports are 10/100/1000BASE-T RJ-45 interfaces, offering Gigabit Ethernet connectivity to end devices. Additionally, the switch includes four 1 Gigabit Ethernet Small Form-Factor Pluggable (SFP) uplink ports for flexible fiber or copper uplink connectivity. For stacking, the rear of the switch houses dedicated StackWise-480 ports. This proprietary stacking technology creates a 480 Gbps ring backplane, delivering resilient, high-bandwidth interconnection between up to 9 stack members. The stacking cables carry both data and control traffic, making the entire stack behave as one switch.

Power Supply and PoE Budget

The "S" suffix typically indicates a standard AC power supply configuration. The WS-C3850-24P-S is equipped with internal, redundant power supply capabilities (with a second power supply being a field-upgradable option) to enhance reliability. Its total PoE power budget is a critical specification, often 740W or higher, which allows it to simultaneously deliver full PoE+ power (30W) to a majority of its 24 ports. This ample budget is essential for powering dense deployments of next-generation wireless access points, such as Cisco's Aironet 2800 or 3800 series, along with a full complement of IP phones and other powered devices.

Unified Wired and Wireless Network Management

The hallmark of the Catalyst 3850 category is its Converged Access model. This integration transcends simple management; it creates a single network entity for both wired switches and wireless access points.

The Integrated Wireless Controller Function

Unlike traditional setups requiring an external appliance, the Catalyst 3850 incorporates a fully functional Wireless LAN Controller within its IOS XE software. This embedded controller can manage a significant number of Cisco Aironet access points (APs), varying by model and software license. The integration means that all network policies—security, QoS, guest access, and more—are configured once in the switch and apply consistently to any device, whether it connects via an Ethernet cable or a Wi-Fi signal. This eliminates policy dissonance and simplifies troubleshooting.

Centralized Configuration and Visibility

Network administrators benefit from a single point of configuration and monitoring. Through the switch's CLI or the embedded web GUI (Device Manager), or through higher-level controllers like Cisco DNA Center, one can provision and manage both the switch ports and the associated wireless network. Features like Radio Resource Management (RRM), client roaming optimization, and CleanAir spectrum intelligence are managed directly from the switch. This centralized visibility provides a holistic view of network health, client connectivity, and application performance across the wired-wireless domain.

Advanced Layer 3 Switching and Routing Capabilities

As a full-featured Layer 3 switch, the WS-C3850-24P-S goes beyond simple access switching. It provides robust routing functionality that can optimize network traffic flow and reduce reliance on core routers for internal routing.

IP Routing Protocol Support

The switch supports static routing and dynamic routing protocols including Open Shortest Path First (OSPF) for enterprise interiors, Enhanced Interior Gateway Routing Protocol (EIGRP), and Border Gateway Protocol (BGP) for more complex scenarios. This allows the switch to act as a routing boundary at the access layer, creating more efficient, segmented networks and facilitating inter-VLAN routing locally.

Enhanced Features for Network Segmentation

Support for a large number of VLANs (4096) and access control lists (ACLs) enables precise network segmentation. Policy-Based Routing (PBR) allows administrators to override traditional routing decisions based on factors like application type or source address. Features like Protocol Independent Multicast (PIM) sparse mode are also supported, which is essential for efficient delivery of multimedia or broadcast content across the network, such as video conferencing or digital signage streams.

Comprehensive Security and Access Control

Security in the Catalyst 3850 is pervasive, designed to protect the network infrastructure, control user and device access, and safeguard data flows.

Network Infrastructure Protection

The switch suite includes features like Control Plane Policing (CoPP) to protect the switch's CPU from malicious traffic, Dynamic ARP Inspection (DAI) to prevent ARP spoofing attacks, and IP Source Guard to prevent IP address spoofing. These features harden the switch itself against common network-based attacks.

User and Device Authentication

A cornerstone of its security is the support for the 802.1X standard for network access control (NAC). This allows for role-based authentication of users and devices before granting network access. Coupled with features like MAC Authentication Bypass (MAB) for devices that don't support 802.1X, and Web Authentication for guests, it creates a flexible yet secure admission framework. Integration with external authentication servers like Cisco ISE (Identity Services Engine) enables advanced policy enforcement and profiling.

TrustSec and Software-Defined Access (SDA) Readiness

The Catalyst 3850 is a key platform for Cisco's TrustSec technology, which uses Security Group Tags (SGTs) to classify traffic. Instead of filtering based on IP addresses (which can change), policies are enforced based on these logical tags, enabling scalable, group-based policies. This foundational capability makes the Catalyst 3850 fully ready for integration into a Cisco Software-Defined Access (SDA) fabric, where it can operate as an access layer node within an intent-based network.

High Availability and Network Resilience

For business-critical networks, uptime is paramount. The Catalyst 3850-24P-S is engineered with multiple layers of redundancy to ensure continuous operation.

Hardware Redundancy Features

The switch supports field-installable, redundant, hot-swappable power supplies and fans. This ensures that a single component failure does not lead to a network outage. The StackWise-480 technology is itself a redundancy mechanism; the stacking ring can withstand a single cable or member failure and continue operating, automatically healing the ring.

Software and Protocol-Driven Resilience

At the protocol level, features like Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP) provide default gateway redundancy for downstream devices. For the wireless controller function, access points configured to be managed by the switch's embedded controller typically support high-availability SSO (Stateful Switchover) when in a stack, allowing wireless client sessions to be maintained during a switchover event.

Quality of Service (QoS) for Application Performance

In a converged network carrying voice, video, data, and wireless traffic, ensuring optimal performance for critical applications is essential. The Catalyst 3850 provides sophisticated QoS mechanisms.

Classification, Marking, and Queuing

The switch can classify traffic based on Layer 2 (CoS), Layer 3 (DSCP), or deep packet inspection. It can then mark, police, and shape traffic flows. With configurable ingress and egress queues, it can prioritize latency-sensitive traffic like voice or video conferencing (using protocols like LLDP-MED for phones) over best-effort data traffic. This granular control guarantees bandwidth and minimizes jitter and packet loss for real-time applications.

Deployment Scenarios and Use Cases

The versatility of the Cisco WS-C3850-24P-S makes it suitable for a wide array of deployment scenarios.

Enterprise Campus Access Layer

Its most common deployment is in wiring closets across corporate campuses. Here, it provides high-density PoE+ for IP phones and wireless access points, while its Layer 3 capabilities allow for local routing between departmental VLANs. The unified management simplifies the support of a mobile workforce.

Large Branch Office or Education Campus

In a large branch office, it can serve as the core networking device, providing routing, switching, and wireless control in a single box. In schools and universities, its high PoE budget supports dense wireless deployments in classrooms and lecture halls, while advanced security features help segment student, faculty, and lab networks.

Mid-Market Core or Small Data Center Aggregation

For mid-sized organizations, a stack of Catalyst 3850 switches can provide a resilient and high-performance network core. Its 10G uplink capabilities (via optional network modules) and routing features make it suitable for aggregating traffic from multiple access switches or even for top-of-rack switching in smaller data center environments where server connectivity and virtualization host connectivity are required.