WS-C3850-12XS-S Cisco Catalyst 3850 12 Port Ethernet Switch

Product Outline

The Cisco WS-C3850-12XS-S Catalyst 3850 is a high-performance enterprise-grade network switch designed for modern data centers and campus networks. Built to deliver reliable 10 Gigabit fiber connectivity, this switch ensures scalable performance, advanced traffic handling, and seamless stacking for growing network infrastructures.

General Information

Manufacturer Details

• Brand: Cisco
• Model Number: WS-C3850-12XS-S
• Series: Catalyst 3850

Hardware Configuration

Form Factor and Build

• Rack-mountable 1RU enclosure
• Designed for enterprise and data center environments

Memory and Storage

• RAM: 4 GB
• Flash Storage: 4 GB

Network Performance and Capacity

Port and Uplink Options

High-Speed Connectivity

• 12 × 10 Gigabit SFP+ optical fiber ports
• Compatible uplink module: C3850-NM-4-10G

Switching and Forwarding Performance

Optimized Data Throughput

• Switching Capacity: 320 Gbps
• Forwarding Rate: 227.28 Mpps

Stacking Capabilities

Scalable Network Expansion

• Supports stacking of up to 9 switches
• Maximum stack bandwidth of 480 Gbps

Physical Dimensions

Size and Measurements

• Width: 44.5 cm
• Depth: 45.0 cm
• Height: 4.45 cm

Cisco Catalyst 3850 Series: The Converged Access Advantage

The Cisco Catalyst 3850 Series represents a paradigm shift in campus networking, introducing the groundbreaking concept of Converged Access. This architectural innovation unites wired and wireless network management, policy enforcement, and data forwarding onto a single, resilient platform. The WS-C3850-12XS-S model stands as a pinnacle of performance within this series, engineered specifically for demanding network aggregation and core distribution roles where high-density 10 Gigabit Ethernet connectivity is non-negotiable. It transcends the traditional definition of a switch, operating as an intelligent network fabric that simplifies operations, accelerates application deployment, and provides unparalleled visibility across the entire connected environment.

Deep Dive: Cisco WS-C3850-12XS-S Hardware Architecture

At its core, the WS-C3850-12XS-S is built for relentless performance and scalability. Its hardware design addresses the critical needs of modern bandwidth-intensive applications, IoT device proliferation, and secure user access.

Chassis & Form Factor

The switch features a compact, yet robust 1RU (Rack Unit) form factor, optimizing data center and wiring closet space. It is designed with front-to-back airflow, making it suitable for standard rack deployments in temperature-controlled environments. The build quality is industrial-grade, ensuring reliable operation 24/7.

Performance Engine: CPU & Stacking Bandwidth

Powered by a multi-core CPU complex, this switch handles advanced features like Cisco IOS XE Software, application visibility, and policy enforcement without breaking a sweat. A key differentiator is its dedicated StackWise-480 technology. The rear of the switch includes special stacking ports that provide an aggregate 480 Gbps of bidirectional stacking bandwidth. This creates a virtual, single-switch management domain of up to 9 units, with a switching capacity of up to 3.84 Tbps in a full stack, all while behaving as one logical device.

Port Configuration & Flexibility

The "12XS" in its model number denotes its primary interface configuration: twelve fixed 10 Gigabit Ethernet SFP+ ports. These ports support a vast array of Cisco SFP+ modules, including:

10GBASE-SR (Multimode Fiber, up to 400m)10GBASE-LR (Single-mode Fiber, up to 10km)
10GBASE-ER (Extended Reach Single-mode)
10GBASE-T Copper (via specific SFP+ transceivers)
1Gbps SFP optics for backward compatibility

This flexibility allows the switch to serve as a top-of-rack aggregation point for access switches, a high-speed backbone link between buildings, or a server access switch for critical infrastructure.

Network Module Uplink Options

Beyond the fixed 12 ports, the WS-C3850-12XS-S includes a single network module slot for ultimate uplink scalability. You can install modules such as the C3850-NM-4-10G (adding four more SFP+ ports) or the C3850-NM-8-10G (adding eight more SFP+ ports), effectively creating a 16- or 20-port 10G switch. This modularity future-proofs your investment.

Power Supply & Fan Redundancy

The switch ships with a single, internal 715W AC power supply. For mission-critical deployments, a second, hot-swappable 715W AC or DC power supply can be added to establish full power redundancy (1+1). The fan tray is also field-replaceable and operates in a redundant N+1 configuration, ensuring continuous cooling even in the event of a fan failure.

The Intelligence Layer: Cisco IOS XE Software & Feature Set

The hardware is empowered by the full-featured Cisco IOS XE Software, the same operating system that runs on the largest service provider and enterprise routers. This provides carrier-class stability, scripting capabilities (Python), and a rich set of features.

Unified Wired & Wireless with Cisco StackWise

This is the cornerstone of Converged Access. When stacked with other Catalyst 3850 switches, the entire stack can seamlessly integrate a Wireless Controller function. You can embed a Cisco 5760 Wireless LAN Controller instance directly on the switch stack, managing hundreds of Cisco Aironet access points. This eliminates the need for a separate physical WLC, reducing cost, complexity, and potential points of failure. Policy set for a wired user is consistently applied to a wireless user, as the control plane is unified.

Advanced Routing & Scalability

Unlike simple Layer 2 switches, the WS-C3850-12XS-S operates as a full Layer 3 routing switch. It supports static routing, RIP, OSPF, EIGRP, and BGP routing protocols. With its performance, it can handle inter-VLAN routing for thousands of users and act as an OSPF Area Border Router (ABR) in larger campus designs. Its IPv6 support is comprehensive, enabling dual-stack implementations for future-proof networking.

Security & Policy Enforcement

Security is embedded at every layer. Key features include:

Cisco TrustSec: Provides software-defined segmentation using Scalable Group Tags (SGT). This allows policy enforcement ("who can talk to whom") based on user identity, not just IP address, simplifying micro-segmentation.
802.1X Network Access Control: Authenticates users and devices before granting network access.
MACsec Encryption (IEEE 802.1AE): Offers hop-by-hop encryption on all 10G ports, ensuring data confidentiality and integrity at the link layer, crucial for protecting sensitive data in transit.
ACLs & Quality of Service (QoS): Provides granular traffic filtering and advanced QoS policies to prioritize voice, video, and critical applications.

Network Visibility with Cisco Application Visibility and Control (AVC)

The switch integrates Deep Packet Inspection (DPI) technology to recognize over 1400 applications. Using NetFlow and Flexible NetFlow exports, it provides detailed reports on application usage, response times, and network performance. This visibility is critical for troubleshooting, capacity planning, and ensuring adherence to business policies.

Ideal Deployment Scenarios for the Catalyst 3850-12XS-S

This switch is not a general-purpose access switch; it is a strategic aggregation and distribution layer device. Its value is realized in specific, performance-sensitive scenarios.

Campus Network Distribution & Core

In a traditional three-tier campus design (Access-Distribution-Core), the WS-C3850-12XS-S excels as a Distribution layer switch. Its high 10G port density connects multiple Access layer switches (e.g., Catalyst 2960-X or 9200 series) via 10G uplinks. Its powerful routing engine handles all inter-VLAN routing, applies security policies, and connects upstream to the Core with high-speed 10G or 40G links (via modules). Its StackWise capability allows multiple distribution switches to be stacked for simplified management and redundancy.

Data Center Top-of-Rack (ToR) Aggregation

In mid-sized data centers or server rooms, it serves as an excellent ToR or end-of-row aggregation switch. Its twelve SFP+ ports can connect directly to high-performance servers with 10G NICs, storage arrays, or virtualization hosts. Features like MACsec provide link-level encryption for sensitive server traffic, while its Layer 3 capabilities support routing within the data center subnet fabric.

High-Density Wireless LAN Aggregation

For organizations deploying a large number of Cisco Aironet 802.11ac Wave 2 or 802.11ax (Wi-Fi 6) access points, each requiring a multi-gigabit (1G/2.5G/5G/10G) uplink, this switch is ideal. It aggregates dozens of APs, and with its embedded wireless controller functionality, it creates a highly scalable and resilient unified wired/wireless solution without an external WLC appliance.

Fiber Optic Backbone & Metro Ethernet

Its support for long-range (LR and ER) SFP+ optics makes it suitable for building-to-building connectivity within a campus or as a customer-premises equipment (CPE) device for Metro Ethernet services, providing a 10G hand-off to service provider networks.