Cisco Catalyst 3850 Replacement Guide: C9300, C9300X or C9500 by MPN

Some Cisco Catalyst 3850 switches are already past their last date of Cisco support. Selected fiber models remain covered only until April 30, 2027. The correct migration target depends on the complete MPN—not simply on the words “Catalyst 3850.”

For most copper access models, Cisco identifies the Catalyst 9300 as the successor. The 1G fiber models move to the C9300-24S. The 10G fiber models generally move to C9300X-12Y or C9300X-24Y. The 48-port 10G fiber models are the important exception: Cisco points those systems to the C9500-48Y4C.

This guide maps the major models, explains what the suffixes mean, and highlights the places where Cisco’s published migration does not produce a one-for-one replacement in port count, speed, stacking, or licensing.

The short answer

Use this as the starting point:

The replacement table is a starting point, not an engineering sign-off. Count the ports actually in use, preserve required speeds and power, then validate optics, software features, and the target license.

First identify which 3850 lifecycle applies

The Catalyst 3850 family does not have one universal support date. Cisco published separate end-of-life notices for the mainstream copper models and the later fiber models.

As of October 2026, the first group is already outside Cisco’s published security and hardware support window. The selected fiber models have a remaining window, but normal software maintenance has already ended. Cisco’s March 2026 recommended-release guidance lists IOS XE 16.12.14 for the 3850 platform; that recommendation does not extend the hardware lifecycle.

The practical lesson is simple: check the full MPN against the applicable Cisco notice. A product-family page that displays a single date can hide a meaningful split between models.

Exact Catalyst 3850 copper replacement map

Cisco’s mainstream 3850 end-of-life notice maps the following common models to the modular-uplink Catalyst 9300 family.

The license suffix does not translate letter for letter

On the 3850, the common final suffixes are:

• -L: LAN Base
• -S: IP Base
• -E: IP Services

On the C9300, the common final suffixes are:

• -E: Network Essentials
• -A: Network Advantage

That means a 3850 ending in -E does not map to a C9300 ending in -E. In Cisco’s copper migration table, both IP Base (-S) and IP Services (-E) models generally map to Network Advantage (-A), while LAN Base (-L) maps to Network Essentials (-E).

This is one reason to match by the complete Cisco replacement table rather than by the last letter alone.

The 24XU multigigabit trap

The WS-C3850-24XU provides 24 multigigabit UPOE copper ports. Cisco’s end-of-life table lists C9300-24U as the replacement, but the C9300-24U is a 24-port 1G UPOE model. It preserves UPOE and the general platform role, but it does not preserve 2.5G, 5G, or 10G downlinks.

If the existing site uses mGig access points, workstations, or other high-speed copper endpoints, compare requirements against a multigigabit model such as the C9300-24UX instead of treating the published migration PID as a drop-in equivalent. The correct answer depends on how many ports need each speed and how much power each endpoint draws.

Exact Catalyst 3850 fiber replacement map

Cisco’s fiber end-of-life notice identifies base replacement PIDs rather than a license-specific orderable SKU for many models.

The 16-to-12 and 32-to-24 mappings are especially easy to misread. Cisco is naming the successor family, not promising that every populated legacy port fits in one new chassis. Inventory active links, reserved growth ports, port channels, and out-of-band connections before choosing the quantity.

C9300 vs C9300X vs C9500-48Y4C

The C9500 recommendation is not just a larger C9300X. It changes the operational model. The WS-C3850-48XS was itself a standalone model without StackWise-480, but a C9500 migration still requires a fresh review of redundancy, software design, airflow, optics, and cabling.

Practical comparisons from the Netmode catalog

24-port PoE+: WS-C3850-24P-S to C9300-24P-A

Compare the WS-C3850-24P-S with the C9300-24P-A.

This is one of the cleanest migrations: 24 PoE+ access ports and an advanced license tier on both sides. The C9300 still requires a deliberate uplink-module choice, and the usable PoE budget depends on the installed power supplies rather than on the chassis name alone.

24-port data: WS-C3850-24T-L to C9300-24T-E

Compare the WS-C3850-24T-L with the C9300-24T-E.

This pairing preserves a 24-port data-only access design and moves from LAN Base to Network Essentials. It is appropriate when endpoint power is supplied separately. If the closet may need phones, cameras, or access points later, compare the cost of the PoE model before locking in a data-only replacement.

Mixed multigigabit: WS-C3850-12X48U to C9300-48UXM

Compare the WS-C3850-12X48U-E with the C9300-48UXM-A.

This is the more natural 48-port mixed-speed migration. The target provides 12 higher-speed multigigabit ports plus 36 ports that support up to 2.5G, along with UPOE and modular uplinks. Confirm the exact speed and power required on every occupied port; “48-port mGig” can describe materially different port mixes.

12-port 10G fiber: WS-C3850-12XS-E to C9300X-12Y-A

Compare the WS-C3850-12XS-E with the C9300X-12Y-A.

Both provide 12 front-panel fiber ports for the migration use case, while the C9300X adds 25G capability and faster stacking. Do not assume an installed SFP or SFP+ is supported merely because it fits the cage. Validate the exact transceiver MPN, speed, fiber type, wavelength, and target IOS XE release.

24-port 10G fiber: WS-C3850-24XS-E to C9300X-24Y-A

Compare the WS-C3850-24XS-E with the C9300X-24Y-A.

This is the closest high-speed fiber transition by port count. The C9300X-24Y provides 24 ports that support 1G, 10G, or 25G and accepts modular uplinks. The migration plan should still account for the target uplink module, software license, optics, and stack topology.

48-port 10G fiber: WS-C3850-48XS-E to C9500-48Y4C-A

Compare the WS-C3850-48XS-E with the C9500-48Y4C-A.

The port layout explains Cisco’s recommendation: 48 high-speed SFP-family ports plus four QSFP-family uplinks on both generations, with the C9500 moving the front-panel ports to 1/10/25G and the uplinks to 40/100G. The physical resemblance should not hide the platform change. Review high availability, airflow direction, rack depth, power, and operating procedures as part of the design.

Five migration checks that prevent expensive mistakes

1. Count active ports, not ports printed in the replacement table

A 16XS can have more than 12 active links, and a 32XS can have more than 24. Include port channels, dark-fiber reservations, monitoring links, and planned growth. Cisco’s family mapping does not eliminate the arithmetic.

2. Separate PoE standard from PoE budget

PoE+, UPOE, and UPOE+ describe per-port power capabilities. The available chassis budget depends on the power-supply configuration and redundancy mode. Record endpoint draw, startup behavior, maximum design load, and required headroom before selecting power supplies.

3. Order the uplink architecture, not just the chassis

The common C9300 and C9300X models in this guide use modular uplinks. A bare switch PID does not automatically provide the uplink ports needed for the cutover. Choose the network module from the required number and speed of links; then verify optics and cables.

Cisco notes that Catalyst 3850 network modules are supported on applicable C9300 models, while C9300X network modules are specific to C9300X. Compatibility still needs to be checked by exact chassis, module, and software release.

4. Treat the stack as a migration project

A Catalyst 3850 cannot remain in a mixed production stack with a C9300 or C9300X. Cisco documents up to nine stacking-capable members for a 3850 stack and up to eight for the C9300 family, so a fully populated nine-member 3850 stack cannot be recreated as one eight-member C9300 stack.

Cisco’s upgrade guide says existing 3850 StackWise cables can be reused for supported C9300 migrations. That can reduce material changes, but it does not make the generations interoperable. Validate cable part numbers and lengths, target stack-member rules, software versions, license levels, election priorities, and the rollback plan.

5. Audit the functions that lived inside the old switch

The 3850 combined wired switching with integrated wireless-controller capabilities in some deployments. A C9300 chassis replacement does not automatically recreate that wireless control-plane role. Also review routing protocols, QoS, authentication, DHCP snooping, device tracking, NetFlow, automation, monitoring, and any feature tied to the old license.

Both generations use IOS XE, but this is not permission to paste the entire old configuration and assume equivalence. Build and test the target configuration against the chosen release.

When buying another 3850 can still make sense

A 3850 can still be a rational purchase when it solves a controlled, short-duration problem:

• A matching spare is needed for an existing stack awaiting a scheduled refresh.
• A lab or staging environment requires the same hardware as production.
• A temporary site has a retirement date before the equipment becomes an operational burden.
• A hard-to-find fiber model is needed to restore service while a migration is prepared.

For mainstream copper models, the decision must acknowledge that Cisco’s published hardware and security support ended in October 2025. For the covered fiber models, the remaining Cisco support window ends April 30, 2027. A lower acquisition price does not restore vendor support or eliminate the labor of a later migration.

For a new long-lived production deployment, the Catalyst 9300, 9300X, or 9500 migration path is normally the more defensible choice.

Catalyst 3850 migration checklist

Before ordering a replacement, document:

• Complete source MPN, including the port-family designator (T, P, F, U, XU, S, or XS) and license suffix (-L, -S, or -E)
• Number of active ports, port channels, reserved ports, and expected growth
• Copper speeds required on every multigigabit port
• PoE standard, measured load, maximum load, and redundancy requirement
• Existing uplink module and target uplink-module MPN
• Every SFP, SFP+, SFP28, QSFP+, or QSFP28 transceiver MPN
• Fiber type, wavelength, connector, distance, and patch-panel path
• Required Network Essentials or Network Advantage features
• Stack member count, stack cables, StackPower design, and software compatibility
• Integrated wireless-controller dependencies
• Routing, QoS, security, automation, and monitoring configuration
• Rack depth, airflow direction, power feeds, grounding, thermals, and acoustics
• Maintenance window, staged configuration, validation tests, rollback, and spare strategy

Final recommendation

Start with Cisco’s published MPN mapping, then challenge it against the real deployment.

For mainstream 24- and 48-port copper models, the C9300 is the normal destination. For 1G SFP access, begin with the C9300-24S. For 12- to 32-port 10G fiber, begin with the C9300X-12Y or C9300X-24Y—but verify that the reduced port-count mappings have enough capacity. For 48-port 10G fiber, begin with the C9500-48Y4C and treat it as an architecture migration, not just a chassis replacement.

The safest purchasing rule is to preserve six things explicitly: port count, port speed, PoE, uplinks, software features, and lifecycle. If any one of those is inferred from the family name alone, the replacement can be wrong even when Cisco lists it in the same migration column.

Frequently asked questions

What is the direct replacement for a Cisco Catalyst 3850?

There is no single replacement MPN. Cisco lists C9300 models for most copper and 1G fiber 3850s, C9300X-12Y or C9300X-24Y for many 10G fiber models, and C9500-48Y4C for the 48-port 10G fiber models.

Is the Cisco Catalyst 3850 still supported?

Most mainstream copper, PoE, UPOE, and mGig 3850 models reached their last date of Cisco support on October 31, 2025. The fiber SKUs covered by Cisco’s separate notice reach their last date of support on April 30, 2027. Check the exact MPN against the relevant notice.

Can a Catalyst 3850 stack with a C9300?

No. The 3850 cannot operate as a mixed stack member with the C9300 or C9300X. Cisco states that existing 3850 StackWise cables can be reused in supported C9300 migrations, but the migration still requires a cutover to a new stack.

Does WS-C3850-24XU map directly to C9300-24UX?

Cisco’s end-of-life table lists C9300-24U, not C9300-24UX, as the formal replacement. However, C9300-24U does not preserve the 3850-24XU’s multigigabit downlinks. If mGig is in use, select the target from actual speed and power requirements rather than relying only on the formal migration PID.

Why does a 32-port 3850 map to a 24-port C9300X?

Cisco lists C9300X-24Y as the migration PID for WS-C3850-32XS models. That is a product-family migration, not a guarantee of equal port density. If more than 24 ports are required, the design needs additional capacity or a different platform choice.

Can existing 3850 optics be reused?

Possibly, but cage type and nominal speed are not enough. Verify the exact transceiver MPN in Cisco’s compatibility information for the target chassis and IOS XE release. Also confirm fiber type, wavelength, distance, and any breakout requirements.

What is the difference between C9300 -E and -A?

-E denotes Network Essentials and -A denotes Network Advantage. Do not translate the final letter directly from the 3850: a 3850 -E means IP Services, while a C9300 -E means Network Essentials.

Sources

• Cisco: End-of-Sale and End-of-Life Announcement for Catalyst 3850 Switches
• Cisco: End-of-Sale and End-of-Life Announcement for C3850 Fiber SKUs
• Cisco: Recommended Releases for Catalyst 3650 and 3850 Platforms
• Cisco: Catalyst 3850 Series Switches Data Sheet
• Cisco: Upgrade Guide from Catalyst 3650/3850 to Catalyst 9300
• Cisco: Catalyst 9300 Series Switches Data Sheet
• Cisco: Catalyst 9500 Series Switches Data Sheet