Cisco WS-C3850-48P-S EoL: Migrate to Catalyst 9300 (C9300-48P-A)

If you still have Cisco Catalyst 3850 48-port PoE switches (PID WS-C3850-48P-S) carrying access-layer traffic, they are now past their final support milestone. Cisco's End-of-Sale and End-of-Life notice for the Catalyst 3850 family set Last Day of Support (LDoS) at October 31, 2025. As of that date, this hardware is fully end-of-life: no TAC cases, no RMA hardware replacement, no software fixes, and no new PSIRT security patches. This guide explains exactly what that means for a WS-C3850-48P-S, why the timing is now urgent rather than aspirational, and how to execute a clean migration to the recommended successor, the Catalyst 9300 48-port PoE+ Network Advantage (PID C9300-48P-A).

What the WS-C3850-48P-S is, and what it is replacing

The WS-C3850-48P-S is the IP Base, PoE+ member of the Catalyst 3850 line: 48 ports of 10/100/1000 (RJ-45) access with IEEE 802.3at PoE+, a 715W default power supply driving roughly 437W of usable PoE budget (expandable to 1100W for the full 30W-per-port budget), and a 480 Gbps StackWise-480 backplane that lets up to nine units stack as one logical switch. Uplinks ride a Network Module slot (the C3850-NM family — 4x1G, 2x10G, or 4x10G SFP+ options). Crucially, this is a perpetual-license box: the feature set is baked into the image tier (IP Base here, versus IP Services), running IOS-XE on the older Polaris/16.x trains. That static licensing model is the single biggest operational difference you will feel when you move to the 9300.

What each end-of-life date actually means

• End of Sale — October 30, 2020: Cisco stopped selling the WS-C3850-48P-S new. Any unit still in service is at least five years into its lifecycle; many are well past their depreciation schedule.
• End of Software Maintenance — October 30, 2021: the last maintenance and bug-fix releases shipped. Since then, IOS-XE on this platform has received no new code, including no fixes for newly discovered defects.
• Last Day of Support (LDoS) — October 31, 2025: the hard wall. Past this date Cisco TAC will not open cases, will not RMA failed hardware or power supplies, and PSIRT will not issue patches for new vulnerabilities affecting this platform. A critical CVE found in 2026 against 3850 code will simply never be fixed.

The recommended replacement: Catalyst 9300 C9300-48P-A

Cisco's bulletin names the Catalyst 9300 48-port PoE+ as the direct successor, and the closest one-for-one match to the WS-C3850-48P-S is the C9300-48P-A — 48 ports of 1G RJ-45 with PoE+, ordered with a Network Advantage license. It is the same form factor and the same access-layer role, but the internals are a generation ahead.

Hardware: same footprint, more headroom

• Switching capacity: the 9300 is built on Cisco's UADP 2.0 ASIC with a multicore x86 control plane, pushing total stacking and switching well beyond the 3850 — StackWise-480 is standard (480 Gbps), and the 9300 series adds an optional StackWise-1T (1 Tbps) tier on higher models.
• PoE: the C9300-48P-A delivers a full 822W PoE+ budget with the standard 1100W supply — enough for 30W (802.3at) on a large share of ports simultaneously, a meaningful step up from the 3850's default budget for dense AP, camera, and phone deployments.
• Uplinks: modular network module slot supporting up to 8x10G, 2x25G, or 2x40G — so you can move from 10G to 25/40G uplinks without a chassis swap, something the 3850's NM slot could not do.
• Stacking and power: StackWise-480 data stacking plus StackPower for shared power resiliency across the stack, and a redundant field-replaceable power supply and fans — the same operational model your team already knows from the 3850.

Licensing: the real change — perpetual to subscription

This is where planning matters most. The 3850's IP Base feature set was a one-time, perpetual entitlement. The 9300 splits entitlement into two layers. First, a hardware-tied perpetual base license (Network Essentials or Network Advantage) governs feature scope — Network Advantage on the C9300-48P-A unlocks the advanced routing, SD-Access fabric edge, flexible NetFlow, and segmentation features that map to and exceed old IP Services. Second, Cisco DNA / Cisco Networking subscription licensing (DNA Advantage to match Network Advantage), typically termed 3, 5, or 7 years, drives Catalyst Center (formerly DNA Center) automation, assurance, and telemetry. All of it is managed in Smart Licensing Using Policy (SLUP) through your Smart Account, not the node-locked PAK files of the 3850 era. Budget for the subscription as a recurring line item and confirm the term aligns with your refresh cycle.

A practical migration plan

1. Assessment and inventory

Inventory every WS-C3850-48P-S by serial, stack membership, IOS-XE version, and network module type. Capture show version, show inventory, show switch (stack topology), and show power inline to record your real PoE draw — this tells you whether a 715W supply has been quietly running close to its budget. Pull the running config off each stack and note which features are actually in use (SVIs, routing protocols, ACLs, QoS policies, 802.1X/MAB, port profiles).

2. License transition

Stand up (or confirm) a Cisco Smart Account and Virtual Account before hardware arrives. New C9300-48P-A units ship as Smart-License-ready; you register them to the Smart Account and assign DNA subscription entitlements. There is no PAK-to-Smart conversion to do for the new gear — the work is making sure the subscription term, quantity, and Virtual Account are correct at order time so the switches activate cleanly. Your authorized partner can pre-stage this.

3. Config and feature parity

IOS-XE on the 9300 is the same CLI dialect, so most of a 3850 config ports over with light editing — interface ranges, VLANs, SVIs, OSPF/EIGRP, ACLs, and QoS translate directly. Validate the deltas: QoS uses the same MQC but verify queue mappings against the UADP 2.0 buffer model; confirm 802.1X/MAB/CoA flows against your ISE policy; and if you plan to adopt SD-Access later, the 9300 is a fabric edge node out of the box, which the 3850 is not. Build and test the target config in a lab stack before touching production.

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

• Rack/power: the C9300-48P-A is 1RU like the 3850. Confirm circuit headroom — a fully loaded PoE+ stack at 1100W supplies draws more than a 715W-era 3850 stack.
• Uplinks/optics: 3850 used C3850-NM modules; the 9300 uses C9300-NM modules. Existing 10G SFP+ optics generally carry over, but plan new modules and any 25/40G optics if you are stepping up uplink speed.
• Stacking: 9300 StackWise-480 cables are not interchangeable with 3850 StackWise cables — order C9300 stacking cables and StackPower cables with the switches.

5. Phased cutover

Migrate stack-by-stack or closet-by-closet during maintenance windows rather than a flag-day swap. Pre-stage each 9300 stack with the tested config and current IOS-XE, then cut uplinks and access ports over per switch, validating PoE, voice, and 802.1X on a few ports before moving the rest. Keep the 3850 stack racked and reachable for a defined rollback window before decommissioning.

6. Secure decommission

Before disposal, wipe configuration and credentials (erase startup-config, delete any saved configs and crypto keys, clear the flash). For federal/DoD and healthcare, follow NIST 800-88 media sanitization and retain a certificate of destruction. An authorized partner can handle compliant decommission, asset disposition, and trade-in credit against the refresh.

Procurement notes for government and enterprise buyers

• TAA compliance: the Catalyst 9300 line is available TAA-compliant for federal contracts — confirm the specific SKU and country of origin on the quote, since TAA status is order-specific.
• Payment and contract vehicles: the C9300-48P-A is purchasable via GPC/purchase card for smaller quantities and through standard government contract vehicles for larger refreshes; ask your partner which vehicle gives you the best pricing and lead time.
• Lead times: 9300 lead times fluctuate with demand and the subscription configuration — order early and lock the DNA term up front to avoid activation delays.
• Source from an authorized partner: buying through an authorized Cisco partner like uniqcli guarantees genuine hardware, valid Smart Account/DNA entitlement, full warranty and support eligibility, and avoids gray-market gear that cannot be registered or supported.

For the full milestone detail on this exact unit, see the WS-C3850-48P-S end-of-life page, or browse the wider Cisco EoL hub to scope an entire fleet. You can compare and configure the replacement directly, and when you are ready, get a refresh quote for the C9300-48P-A — including TAA-compliant SKUs, the right Network Advantage and DNA term, stacking cables, and optics — built to land before your audit does.