WS-C3750X-48P-S End of Life: Migration to Catalyst 3850

If you still have Cisco Catalyst 3750-X 48-port PoE switches (WS-C3750X-48P-S) carrying production traffic, you are running hardware that Cisco stopped selling on October 30, 2016 and stopped supporting entirely on October 31, 2021. That second date is the one that matters: the Last Day of Support (LDoS) has passed, which means these switches are not merely old, they are unsupportable. There are no more software fixes, no security patches, and no TAC case or RMA you can open when one fails. This guide explains what each milestone actually means for your fleet, why the Catalyst 3850 48-port PoE (WS-C3850-48P-S) is the named successor, what concretely improves when you move, and how to execute the migration cleanly in a regulated environment.

Where the 3750-X stands today

The 3750-X was a genuine workhorse: a 1RU stackable access switch with 48 ports of 10/100/1000 PoE+, StackWise Plus stacking, modular uplinks via the C3KX network module slot, and optional StackPower for shared power across a stack. The -S suffix denotes the IP Base feature set, which gives you Layer 2 plus basic Layer 3 (static routing, RIP, and limited dynamic routing) but not the full IP Services routing capabilities. It ran classic Cisco IOS on a PowerPC control plane with node-locked, right-to-use style licensing rather than today's Smart Licensing. For its era it was excellent. Today every one of those characteristics is a liability.

What each milestone date means in practice

• End of Sale (Oct 30, 2016): Cisco stopped taking new orders. Any unit you buy after this is used or new-old-stock, never freshly manufactured.
• End of SW Maintenance (Oct 30, 2017): Cisco stopped releasing maintenance IOS rebuilds. Bug fixes effectively froze; only severe security fixes continued, and only until LDoS.
• Last Day of Support (Oct 31, 2021): The hard stop. No TAC, no RMA, no PSIRT patches, no software downloads guaranteed. Hardware and software are both fully retired.

The recommended replacement: Catalyst 3850 48-port PoE

Cisco's EoL bulletin named the Catalyst 3850 (WS-C3850-48P-S for the IP Base, 48-port PoE+ variant) as the migration target, and it is a like-for-like fit in form factor while being a generational leap underneath. The 3850 introduced the Unified Access Data Plane (UADP) ASIC, the same programmable silicon family that carried forward into the Catalyst 9000 line, which is why a 3850 config translates far more cleanly to a modern 9300 later than a 3750-X config does.

What concretely gets better

• Stacking bandwidth: StackWise Plus on the 3750-X tops out around a 32 Gbps stack ring. The 3850 uses StackWise-480, a 480 Gbps backplane, roughly a 15x increase in stack fabric for east-west traffic and faster failover.
• Switching capacity: the 3850 delivers up to 176 Gbps switching and far higher forwarding rates than the 3750-X, giving real headroom as endpoints move from 100 Mbps to gigabit and edge density climbs.
• Operating system: the 3850 runs IOS-XE, not classic IOS. That means a modern Linux-based control plane, model-driven programmability (NETCONF/YANG), patchability, and a smoother automation story versus the monolithic IOS image on the 3750-X.
• PoE budget: both deliver PoE+ (up to 30W per port), but the 3850 with the larger 1100W power supply provides a bigger total PoE budget, supporting more high-draw devices (multi-radio APs, PTZ cameras, video phones) at full power simultaneously.
• Uplinks and optics: the 3850 network module options scale beyond the 3750-X, adding 4x10G and 2x40G uplink modules versus the 3750-X's typical 2x10G ceiling, so your distribution uplinks are not the bottleneck.
• Wireless: the 3850 can act as a Converged Access wireless controller, terminating APs directly on the switch, an option the 3750-X never had.
• Licensing: the 3750-X used older node-locked permanent/RTU licensing. The 3850 moves toward Cisco's Smart Licensing model. This is a real operational change to plan for, not just a paperwork swap.

A practical migration plan

1. Assessment and inventory

Pull the exact PIDs, serial numbers, IOS versions, and stack membership from every 3750-X stack (show version, show switch, show inventory). Capture PoE draw per closet (show power inline), uplink types and optics in use, and the IP Base feature set you actually depend on. This baseline drives both your bill of materials and your config-parity checklist.

2. License transition

Map your old IP Base entitlement to the 3850's licensing tier and plan for Smart Licensing onboarding (Smart Account / Cisco Smart Software Manager). Do this before the gear arrives so units register and activate the right feature set on day one rather than running in eval mode.

3. Config and feature parity

Do not blind-paste 3750-X IOS into a 3850. The CLI is largely familiar but IOS-XE differs in interface naming, licensing commands, and some defaults. Rebuild VLANs, trunking, SVIs, static/RIP routing, DHCP snooping, port security, 802.1X/MAB, and QoS to match, then diff the running configs feature by feature. Validate stack priorities and provisioning before cutover.

4. Physical: rack, power, PoE, uplinks, optics, stacking

Both switches are 1RU and use the same rack rails footprint, so closet space is rarely a blocker. Confirm power: the 3850 PoE models draw appropriately for the budget you size, so verify circuit and PDU headroom. StackWise-480 uses new stacking cables (not the 3750-X StackWise Plus cables), so order those with the switches. Reuse SFP/SFP+ optics where compatible, but verify each optic against the 3850 compatibility matrix before assuming reuse.

5. Phased cutover

Migrate closet by closet, never the whole campus at once. Stage and pre-configure each 3850 stack on the bench, schedule a maintenance window, move uplinks and access cabling, verify endpoints (PoE up, 802.1X auth, voice VLAN, routing reachability), then monitor for a full business day before decommissioning the 3750-X it replaced.

6. Secure decommission

Wipe configs (write erase plus deleting vlan.dat and any flash artifacts), remove the device from monitoring/NAC/RADIUS, and follow your data-sanitization policy for the asset. For federal and DoD, document disposal per your media handling and property control requirements.

Procurement notes for government and enterprise

• TAA compliance: confirm country-of-origin on every unit if you sell to federal/DoD/SLED. We source TAA-compliant Catalyst 3850 (and 9300) hardware for these contracts.
• GPC and purchase-card payment: micro-purchase and card-payable orders are supported, useful for closet-by-closet phased refreshes that fit under thresholds.
• Lead times: because the 3850 is retired, supply is finite. Plan procurement early and reserve stock so your phased cutover is not stalled waiting on hardware.
• Authorized partner sourcing: buying from an authorized Cisco partner protects you on TAA documentation, genuine-hardware assurance, and licensing transfer, which matters far more than chasing the cheapest gray-market listing for an end-of-support replacement.

Bottom line: the WS-C3750X-48P-S is past its last day of support and carries real audit and reliability risk every day it stays in production. The Catalyst 3850 48-port PoE is a clean, named upgrade path, and the 9300 is the current shipping option if you want to leapfrog further. Review the full dates and replacement detail on the WS-C3750X-48P-S EoL page, check the rest of your fleet on the Cisco EoL hub, and browse the replacement in our catalog. When you are ready to scope the refresh, request a TAA-compliant, GPC-payable replacement quote and we will size the right 3850 or 9300 build for your closets.