WS-C3850-24XS-S Cisco Catalyst 3850 24 Ports Layer 3 Switch

The Catalyst 3850 Series: Converged Access

The Cisco Catalyst 3850 Series stackable switching platform represents a paradigm shift in campus network design, unifying core switching functions with advanced wireless LAN controller capabilities. At the heart of this series is the WS-C3850-24XS-S model, a high-performance, 24-port 10 Gigabit Ethernet switch engineered to meet the escalating demands of bandwidth-intensive applications, converged media, and the Internet of Things (IoT). This category encompasses switches designed for the network edge where performance, security, and programmability converge to create a resilient, scalable, and intelligent foundation for business operations.

Unlike traditional standalone switches, the Catalyst 3850 with its Unified Access Data Plane (UADP) application-specific integrated circuit (ASIC) delivers consistent policy and application visibility across both wired and wireless clients. This convergence simplifies network architecture, reduces operational overhead, and provides a seamless user experience regardless of how devices connect to the network. The Cisco WS-C3850-24XS-S is specifically engineered for aggregation and small core deployments, featuring high-density 10GE uplinks and full Layer 3 routing capabilities, making it an ideal cornerstone for building a robust, future-proof campus fabric.

Deep Dive: Cisco WS-C3850-24XS-S Specifications

This specific model is defined by a compelling set of hardware specifications that cater to performance-critical environments. It is designed to deliver wire-speed throughput across all ports while supporting advanced features without degradation.

Hardware Specifications & Port Configuration

The physical architecture of the switch is built for speed and flexibility at the network edge.

Front-Panel Port Density

24 x SFP+ Ports: All twenty-four ports are 10 Gigabit Ethernet SFP+ interfaces, providing immense bandwidth for server connectivity, uplinks to core switches, or high-speed connections to other access switches. This uniform high-density design eliminates bottlenecks.
Stacking & Uplink Flexibility: These ports are multi-functional. They can be used as standard 10GE data ports, or dedicated for switch stacking via Cisco StackWise-480 technology, creating a virtual, single switching unit of up to 9 switches.

Performance & Switching Capacity

Stacking Bandwidth: Up to 480 Gbps of dedicated stacking bandwidth using the Cisco StackWise-480 technology, ensuring that the stack ring does not become a performance bottleneck.
Forwarding Rate: Capable of forwarding over 250 million packets per second (Mpps), enabling it to handle large volumes of small and large frames with ultra-low latency.
Switch Fabric: A non-blocking architecture ensures that the internal switching capacity can handle full wire-speed traffic on all ports simultaneously, which is critical for data center and high-performance computing (HPC) access layers.

Unified Access Data Plane (UADP) ASIC: The Intelligence Core

The defining technological innovation in the Catalyst 3850 series is the UADP ASIC. This custom-designed chip is more than just a switching engine; it's a programmable processor that enables feature consistency.

Key Capabilities Enabled by UADP

Converged Access: Embeds a wireless LAN controller function within the switch, allowing direct management of up to 50 access points and 2000 wireless clients per switch, or scaled across a stack.
Advanced Programmability: Supports features like Cisco Application Visibility and Control (AVC), NetFlow, and Flexible NetFlow with detailed metadata collection, providing deep application-level insights for analytics and security.
Consistent QoS & Security: Applies identical quality of service (QoS) policies and access control lists (ACLs) to traffic, whether it originates from a wired desktop or a wireless laptop, ensuring uniform treatment across the network.

Comprehensive Layer 3 Routing & Network Services

The "-S" designation in WS-C3850-24XS-S signifies the inclusion of the IP Services feature set. This is the most comprehensive software license tier, unlocking full Layer 3 dynamic routing protocols and advanced services for enterprise and data center deployments.

Dynamic Routing Protocol Support

This switch can function as a true router within the campus, supporting complex network segmentation and efficient path selection.

Interior Gateway Protocols (IGPs)

Open Shortest Path First (OSPF): Full support for OSPFv2 and OSPFv3, including areas, virtual links, and various LSA types, enabling scalable hierarchical network design.
Enhanced Interior Gateway Routing Protocol (EIGRP): Support for both IPv4 (EIGRP) and IPv6 (EIGRPv6), offering fast convergence and efficient bandwidth usage through advanced distance vector algorithms.
Routing Information Protocol (RIP): Support for RIPv1, RIPv2, and RIPng for IPv6, useful in legacy or simple network environments.

Border Gateway Protocol & Multicast

BGP (Border Gateway Protocol): Full BGP-4 support for autonomous system (AS) path manipulation and policy-based routing, allowing the switch to participate in large-scale enterprise or service provider edge routing.
Protocol Independent Multicast (PIM): Robust support for PIM Sparse Mode (PIM-SM), PIM Dense Mode (PIM-DM), and PIM Sparse-Dense Mode for efficient multicast traffic distribution for applications like video conferencing and media streaming.

Advanced Network Services & Virtualization

Beyond basic routing, the IP Services software enables sophisticated network segmentation and resiliency features.

Network Virtualization & Overlays

Multiprotocol Label Switching (MPLS): Supports MPLS forwarding and Layer 3 VPNs (L3VPN), enabling the switch to be deployed in service provider or large enterprise environments requiring traffic engineering and network virtualization.
Virtual Routing and Forwarding (VRF-Lite): Allows for the creation of multiple, isolated routing tables on a single physical switch, enabling secure multi-tenancy and separation of traffic for different departments or user groups (e.g., guest, employee, IoT).

High Availability: StackWise-480 & Network Resiliency

For mission-critical environments, the Catalyst 3850 series provides exceptional resiliency through hardware redundancy and intelligent software features.

Cisco StackWise-480 Technology

This proprietary stacking technology is a cornerstone of the platform's scalability and high availability.

How StackWise-480 Works

Up to nine individual Catalyst 3850 switches can be connected via special cables to form a single logical switch, or "stack." The 480 Gbps ring architecture aggregates the bandwidth of all member switches' backplanes.

Benefits of a Single Logical Stack

Simplified Management: The entire stack is managed as one entity through a single IP address, drastically reducing configuration and monitoring complexity.
Increased Resiliency: The stack ring is bidirectional. If a cable fails or a switch is removed, the stack intelligently reconverges within milliseconds, maintaining data flow.
Flexible Scalability: Bandwidth and port density can be increased incrementally by adding another switch to the stack, without complex reconfiguration.
Stateful Switchover (SSO): In a stack, one switch acts as the active controller. If it fails, a standby switch in the stack assumes the active role seamlessly, with no disruption to user sessions or Layer 2/Layer 3 protocols.

Software & Power Redundancy

Beyond stacking, the switch is designed with multiple layers of redundancy.

Dual, Hot-Swappable Power Supplies: The switch supports optional, field-replaceable power supplies for 1+1 redundancy, ensuring continuous operation in case of a power supply failure.
Modular Fans: The fan tray is also hot-swappable, allowing for replacement without downtime.
Cisco IOS XE Software: The robust, modular operating system supports in-service software upgrades (ISSU) when deployed in a stack with SSO, allowing for patching and upgrades with minimal to zero downtime.

Enterprise-Grade Security & Programmability

In today's threat landscape, network access control and visibility are paramount. The Catalyst 3850 provides a comprehensive, identity-aware security framework.

Identity-Based Networking with Cisco ISE

The switch is a key enforcement point for Cisco's Identity Services Engine (ISE), enabling policy-based access control.

802.1X Authentication: Provides port-based network access control (NAC) for both wired and wireless users, ensuring only authorized devices can connect.
TrustSec® Technology: Uses Scalable Group Tags (SGTs) to classify traffic based on user/device identity. Security policies (access controls) are then enforced based on these tags, not just IP addresses, simplifying policy management across the network.
MACsec Encryption: Supports 802.1AE MACsec encryption on all ports, providing hop-by-hop data confidentiality and integrity for sensitive traffic traversing the switch infrastructure.

Network Programmability & Automation

The platform is built for the software-defined era, offering multiple interfaces for automation.

Programmability Interfaces

Python Scripting: The Cisco IOS XE operating system has an embedded Python interpreter, allowing network administrators to write scripts that run directly on the switch for automated configuration, health checks, and remediation.
RESTful APIs: Provides a modern, model-driven REST API for programmatic management, configuration, and telemetry collection, enabling integration with custom applications and network automation tools like Ansible or Puppet.
OpenDaylight & Controller Compatibility: Can be managed by software-defined networking (SDN) controllers, including the Cisco DNA Center, for intent-based networking across the campus.

Primary Use Cases & Deployment Scenarios

The Cisco WS-C3850-24XS-S is versatile, but its hardware profile makes it exceptionally suited for specific roles in the network hierarchy.

Campus Core & Aggregation Layer

In mid-sized to large campus networks, this switch excels as a distribution or core layer device.

Distribution Switch: Aggregates traffic from multiple access-layer switches (including 3850s with 1G ports). Its high 10GE port density and Layer 3 routing capabilities make it ideal for inter-VLAN routing and policy enforcement.
Small/Mid-Size Core: Serves as the heart of a campus network, connecting distribution blocks, data centers, and WAN routers. Its high throughput and routing protocol support ensure efficient traffic transport.

Data Center Top-of-Rack (ToR) Switch

With twenty-four low-latency 10GE ports, it is perfectly suited for server access in enterprise data centers or high-performance computing clusters.

Server Connectivity: Provides high-bandwidth connections to physical servers, storage arrays, and network appliances.
Virtualization Host Uplinks: Connects to hypervisor hosts (VMware ESXi, Microsoft Hyper-V) where multiple virtual machines require aggregated 10GE uplinks.

High-Performance Access Layer

For environments where end-users or devices require extreme bandwidth directly at the edge.

Engineering & Media Workstations: Directly connects to workstations used for CAD/CAM, 4K/8K video editing, and scientific simulation, where local file servers are accessed at 10G speeds.
Specialized IoT & Medical Imaging: Connects high-data-rate devices like medical imaging machines (MRI, CT scanners) or broadcast equipment that generate massive files.