WS-C3850-12S-S Cisco Catalyst 3850-12s-s Managed Desktop, Rack-mountable Switch

Product Outline

The Cisco WS-C3850-12S-S Catalyst 3850 Series is a high-performance, enterprise-grade managed switch designed for modern networks that demand reliability, scalability, and advanced Layer 3 capabilities. Built by Cisco Systems, this compact yet powerful switch is ideal for business environments requiring secure, flexible, and high-speed connectivity.

General Product Details

Manufacturer Information

• Brand: Cisco Systems, Inc.
• Model / SKU: WS-C3850-12S-S
• Product Line: Cisco Catalyst 3850 Series

Device Classification

• Managed Layer 3 Ethernet Switch
• 12-Port Gigabit SFP Configuration
• Stackable Network Switch

Design & Form Factor

Physical Specifications

• Desktop and rack-mountable design
• 1U compact enclosure
• Suitable for enterprise wiring closets and data centers

Network Performance & Throughput

Switching Capabilities

• Switching Capacity: 68 Gbps
• Forwarding Rate: 68.4 Million Packets Per Second (Mpps)
• Stacking Bandwidth: Up to 480 Gbps with Cisco StackWise-480

Port Configuration

• 12 x Gigabit Ethernet SFP ports
• Optimized for fiber-based network deployments

Capacity & Scalability

Routing & Table Sizes

• IPv4 Routing Entries: Up to 24,000
• NetFlow Entries: 24,000
• MAC Address Table: 32,000 entries
• Switched Virtual Interfaces (SVIs): 1,000

Advanced Frame Support

• Jumbo Frames supported up to 9,198 bytes
• Enhanced data transfer efficiency

Routing & Management Protocols

Supported Routing Protocols

• RIP v1 and v2
• EIGRP
• RIPng for IPv6 environments

Key Features & Functionalities

Security & Network Control

• Access Control Lists (ACL)
• Dynamic ARP Inspection (DAI)
• DHCP Snooping
• RADIUS authentication support
• STP Root Guard and UDLD

Switching & VLAN Technologies

• VLAN and trunking support
• Dynamic Trunking Protocol (DTP)
• Link Aggregation (LACP and PAgP)
• Rapid Spanning Tree (RSTP), MSTP, and PVST+

Performance Optimization

• Quality of Service (QoS)
• Layer 3 load balancing
• Shaped Round Robin (SRR)
• Energy Efficient Ethernet

Cisco Exclusive Technologies

• Cisco StackWise-480 Technology
• Cisco StackPower Technology
• Flexible NetFlow (FNF)
• Remote Switch Port Analyzer (RSPAN)

Standards & Compliance

IEEE Supported Standards

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

Power & Reliability

Power Specifications

• AC Input: 120V / 230V
• Frequency: 50/60 Hz
• Optional redundant power supply support

Core Architecture and Technological Advantages

At the heart of the Catalyst 3850-12S-S is a forward-thinking design that converges wired and wireless network management into a single, cohesive system. This convergence is more than just a feature; it's a fundamental architectural shift that simplifies operations, reduces overhead, and enhances security.

Unified Access Data Plane (UADP) ASIC

The custom UADP ASIC is the engine of the Catalyst 3850 series. It delivers consistent, application-aware services across all ports, enabling deep programmability and visibility. This chipset allows for features like flexible NetFlow, advanced quality of service (QoS), and robust security policies to be executed at wire speed without compromising performance. The programmability inherent in the UADP ASIC also means the switch can adapt to new protocols and standards through software updates, ensuring longevity and protecting your capital investment against evolving network demands.

Converged Wired and Wireless Networking

Unlike traditional switches that manage only wired clients, the Catalyst 3850 series operates with a Wireless LAN Controller (WLC) embedded directly in the switch stack. This allows network administrators to manage both wired Ethernet ports and wireless access points (like the Cisco Aironet series) from a single, unified management interface. This convergence eliminates the need for separate wireless controller appliances in small to medium deployments, reducing complexity, cost, and points of failure. Policies configured for wired users are seamlessly extended to wireless users, ensuring a uniform access experience and security posture.

StackWise-480 Technology

For scalability, the WS-C3850-12S-S supports Cisco's StackWise-480 technology. This allows up to nine individual Catalyst 3850 switches to be logically grouped into a single, virtual switching unit with a collective backplane of 480 Gbps. From a management perspective, the entire stack appears as one device, simplifying configuration, monitoring, and troubleshooting. StackWise-480 also provides high availability; if the master switch in the stack fails, a subordinate switch automatically takes over with minimal disruption, ensuring business continuity.

Hardware Specifications and Physical Design

The WS-C3850-12S-S is built for versatility and reliability in demanding environments. Its physical design supports a range of deployment scenarios, from wiring closets to server rooms.

Port Configuration and Uplink Capabilities

This model is equipped with 12 fixed SFP (1GbE) ports. The use of SFP ports provides exceptional flexibility for uplink connections. Network administrators can choose the appropriate SFP module—such as short-range multi-mode (SX), long-range single-mode (LX/LH), or even copper (T)—to match the distance and media requirements of the connection to the core switch or service provider equipment. This makes the 3850-12S-S an excellent choice for fiber aggregation, backhaul, or as a top-of-rack switch in server environments where high-speed, noise-free fiber connections are preferred.

Form Factor and Deployment Options

Engineered as a 1-Rack-Unit (1RU) switch, it is designed for standard 19-inch rack mounting, making it a perfect fit for organized IT closets and data centers. Importantly, Cisco also includes desktop mounting kit options, recognizing that not all deployment scenarios have dedicated rack space. This dual-design approach allows the switch to be conveniently placed on a shelf or desk in smaller offices, retail locations, or classrooms without sacrificing any functionality.

Performance and Power Specifications

The switch delivers non-blocking, wire-speed performance on all ports simultaneously, ensuring that network bottlenecks are eliminated even during peak traffic loads. It supports advanced energy-saving features like Energy Efficient Ethernet (EEE) and various power-drawing modes that scale with connected device demand. The model can be configured with either an AC power supply or, optionally, with Direct Current (DC) or Power over Ethernet (PoE+) power supplies for models with copper ports, though the 12S-S itself does not provide PoE as it is an SFP-only switch.

Software Capabilities: IP Base Feature Set

The "IP Base" software image pre-installed on the WS-C3850-12S-S provides a comprehensive suite of Layer 2 and Layer 3 features suitable for most enterprise branch and campus access layer deployments. It represents a robust middle ground between the essential Layer 2-only LAN Base image and the fully featured IP Services image.

Layer 3 Routing Intelligence

IP Base includes support for essential static routing and Routing Information Protocol (RIP) versions 1 and 2. For more dynamic environments, it supports Open Shortest Path First (OSPF) for efficient intra-domain routing and Enhanced Interior Gateway Routing Protocol (EIGRP) stub routing. This level of routing capability allows the switch to perform inter-VLAN routing locally, offloading this task from the core router and significantly improving network performance and reducing latency for internal traffic between different subnetworks.

Advanced QoS and Security Policies

Quality of Service is critical in converged networks carrying voice, video, and data. The IP Base image supports sophisticated classification, marking, policing, and queuing based on Layer 2, 3, and 4 parameters. This ensures that real-time applications like VoIP (Voice over IP) and video conferencing receive priority, guaranteeing clear, jitter-free communication. On the security front, beyond standard ACLs (Access Control Lists), it offers features like Dynamic ARP Inspection (DAI), IP Source Guard, and DHCP Snooping to protect against common man-in-the-middle and spoofing attacks at the access layer.

Network Management and Programmability

Management is facilitated through multiple interfaces: a familiar Cisco IOS Command-Line Interface (CLI), a web-based graphical interface (GUI), and support for centralized management via Cisco Prime Infrastructure or Cisco DNA Center. The switch fully supports SNMP (v1, v2c, and v3), syslog, and RMON for comprehensive monitoring. Furthermore, with the UADP ASIC, the switch lays the groundwork for software-defined access (SD-Access) concepts, providing APIs for programmability and automation, which are key for modern DevOps practices in IT.

Primary Use Cases and Deployment Scenarios

The specific port configuration and feature set of the WS-C3850-12S-S make it uniquely suited for several key networking roles.

Fiber Aggregation Switch for Branch Offices

In a distributed enterprise with multiple branch offices, the 3850-12S-S excels as an aggregation switch. Its 12 SFP ports can be used to connect to multiple access switches (e.g., Catalyst 2960-L series with fiber uplinks) over longer distances via fiber, backhauling all branch traffic reliably to the Wide Area Network (WAN) router or directly to the corporate data center over a Metropolitan Area Network (MAN). Its Layer 3 routing capabilities allow it to efficiently handle inter-VLAN traffic within the branch locally.

Server Access or Top-of-Rack (ToR) Switch

In server rooms or small data centers, servers often come equipped with SFP-based network interfaces for high-speed, low-latency connections. The 3850-12S-S provides a dense, 1RU footprint for connecting up to 12 servers directly with dedicated fiber or copper SFP links. Stacking capability allows this capacity to be multiplied, creating a highly available and easily managed server access layer.

High-Speed Network Backbone for Campuses

For smaller campus environments or as a building distribution switch, the 12S-S can form a high-speed fiber backbone. It can aggregate traffic from multiple floors or wings of a building that are connected via fiber runs, performing routing and policy enforcement before sending traffic to the core. Its unified wireless controller functionality also allows it to directly manage and terminate traffic from access points deployed throughout the building.

Investment Protection and Longevity

Built on the same UADP ASIC as the next-generation Catalyst 9000 series, the 3850 platform is designed to support new features and capabilities through software updates. This "future-ready" design protects against obsolescence. Furthermore, its stacking technology allows network capacity to be increased modularly, enabling growth without a costly "forklift" upgrade.

Enterprise-Grade Reliability

Cisco's reputation for building reliable, carrier-grade networking equipment is embodied in the Catalyst 3850. Features like redundant, hot-swappable power supplies (with appropriate modules), robust StackWise redundancy, and field-proven Cisco IOS XE software ensure high availability and network uptime, which is critical for business operations.

Comparing Within the Catalyst 3850 Family

Understanding where the 12S-S model fits within the broader Catalyst 3850 portfolio is key to making the right selection.

12S-S vs. Models with Copper Ports (e.g., 48P)

The primary difference lies in the port type and density. Models ending in "P" or "T" feature 10/100/1000BASE-T copper ports for connecting end-user devices like PCs, phones, and cameras. The 12S-S, with its 12 SFP ports, is designed exclusively for uplinks and fiber connections. It is often deployed in tandem with copper switches, acting as their aggregation point.

IP Base vs. LAN Base vs. IP Services

The Catalyst 3850 comes with three main software tiers. LAN Base offers robust Layer 2 features only. IP Base (featured on this model) adds essential Layer 3 dynamic routing (OSPF, EIGRP stub). IP Services provides full Layer 3 capabilities, including advanced protocols like Border Gateway Protocol (BGP) and Protocol Independent Multicast (PIM), required for large enterprise cores or service provider edges. For most access/distribution layer roles, IP Base is the optimal, cost-effective choice.