Cisco Catalyst 3750-X & 3850 to Catalyst 9300 Upgrade Guide: Why, What, and How

Aug 18 , 2026 7

The Catalyst 3750-X and 3850 have powered enterprise access layers for over a decade. Both are now deep in Cisco's end-of-life process, so the question has shifted from "if" to "when and how." This guide covers why to move now, which Catalyst 9300 to choose, how to migrate safely, and what the sensible spending options are.

Why Upgrade from the 3750-X / 3850

The Catalyst 3750-X has been out of sale for many years and its last day of support has passed: no new software releases, no fixes for vulnerabilities discovered today, and no vendor hardware support. If a unit or power supply fails, you depend entirely on secondary-market spares.

The Catalyst 3850 is newer, but Cisco has published end-of-sale and end-of-life milestones for the series: new hardware sales have stopped, and software and support coverage wind down on a fixed schedule. Each additional year means scarcer parts and pricier support contracts.

Beyond lifecycle status, both platforms show their age technically:

• Uplinks and fabric. The 3750-X tops out at 2x10G uplink modules and 64 Gbps of StackWise Plus stacking bandwidth. The 3850 is stronger (StackWise-480, up to 2x40G uplink modules), but neither matches modern expectations for 10G/25G uplink density at the access layer.
• No mGig or UPOE on the 3750-X. Wi-Fi 6/7 access points, PTZ cameras, and thin clients increasingly need multi-gigabit access or more than 30W per port.
• Weak automation. The 3750-X runs classic IOS with CLI/SNMP-only management; the 3850 runs IOS-XE but on a code train that no longer receives meaningful feature investment. Neither fits modern provisioning and telemetry workflows.
• Hidden cost of staying. Maintenance premiums rise as parts dry up, repair times stretch when spares are scarce, and security exposure grows with every unpatched advisory.

To be fair: a healthy 3750-X or 3850 can still serve well in non-critical or isolated environments — labs, test segments, or air-gapped networks. Prioritize production access layers where support coverage, security, and performance genuinely matter.

What to Upgrade To: Catalyst 9300

The Catalyst 9300 is Cisco's current enterprise access switch and the direct successor to the 3650/3850 line: same 1U form factor, IOS-XE, modular uplinks, and full investment in current software releases. LinkNewNet currently stocks:

• 24-port data: C9300-24T-A
• 24-port PoE+: C9300-24P-A
• 24-port UPOE: C9300-24U-A, C9300-24U-E
• 48-port data: C9300-48T-E
• 48-port PoE+: C9300-48P-E
• 48-port UPOE: C9300-48U-A, C9300-48U-E, C9300-48UN-A (high-fabric variant)
• 48-port Multigigabit UPOE: C9300-48UXM-A
• Value line with fixed uplinks: C9300L-24T-4G-A, C9300L-48P-4G-E

Suffixes: -A SKUs ship with a Network Advantage license, -E SKUs with Network Essentials.

Beyond the spec sheet, current IOS-XE brings zero-touch provisioning, streaming telemetry, and API-driven management that the 3750-X generation simply cannot offer.

Is it a drop-in replacement? Mostly. The 9300 fits the same racks and your existing structured cabling carries over. What changes: power supplies (PWR-C1 family — size them to your PoE budget), uplink modules (3850-era modules do not fit; order C9300-NM modules plus optics), and stack cabling.

Choosing the right model:

• 24 vs. 48 ports: match current usage plus roughly 20% growth; 48-port models usually win on cost per port.
• PoE vs. UPOE vs. mGig: phones and basic APs are fine on PoE+ (P models). Wi-Fi 6/7 APs and PTZ cameras call for UPOE (U models, 60 W per port). If access links themselves need more than 1G, choose the multigigabit C9300-48UXM.
• Uplinks: if you want 10G/25G/40G flexibility now or later, buy a 9300 with the right C9300-NM module. If simple fixed 4x1G uplinks are enough, the 9300L is the cheaper path.
• 9300 vs. 9300L: the 9300 gives modular uplinks, higher stacking bandwidth (480 vs. 320 Gbps), and the fuller feature set; the 9300L is a cost-optimized fixed-configuration option for smaller sites.
• Bigger needs: for very high uplink density or aggregation roles, step up to the Catalyst 9300X or 9500 families.

Migration: What to Watch For

Configuration. VLAN, interface, and spanning-tree concepts carry over, but do not paste old configs blindly. Moving from the 3750-X means moving from classic IOS to IOS-XE: some commands are deprecated, the QoS model differs, and there is no direct image upgrade — plan a fresh install on a current IOS-XE release. Coming from a 3850 (also IOS-XE) is much closer, but still validate against your target release rather than copy-pasting.

Stacking. You cannot mix 3750-X/3850 and 9300 members in one stack — generations do not share a StackWise domain. The standard approach: build the new 9300 stack alongside the old one, mirror VLANs, trunks, and port-channels, reuse the same member numbering where practical to keep port mapping simple, and move access cables over in a planned window. Ring-topology cabling and stackwise priority settings matter as much as on the old platform.

Hardware. Budget PWR-C1 power supplies sized for your PoE load, C9300-NM uplink modules, optics, and stack cables. Old 3850/3750-X network modules will not fit the new chassis; physically, a 1U swap in the existing rack is straightforward.

Licensing. Catalyst 9300 licensing is per-switch: Network Essentials or Network Advantage (Advantage includes everything in Essentials plus advanced features). Choose the tier at order time — that is what the -A/-E suffix on each SKU encodes — and register for Smart Licensing during deployment.

Recommended cutover sequence:

• Audit the existing stack: full config backup, port map, PoE budget, uplink inventory.
• Bench-build the 9300 stack: target IOS-XE version on all members, translated config, licenses registered.
• Test in the lab against a copy of production: VLANs, trunks, port-channels, PoE devices.
• Schedule the maintenance window, swap cables following the port map, verify, and monitor.
• Keep the old stack racked, labeled, and powered down but reachable for an agreed rollback period.

Post-cutover verification checklist: IOS-XE version identical on all stack members; stack roles and redundancy as designed; license state registered and in compliance; PoE consumption with comfortable headroom; no interface errors or duplex mismatches on reused links; spanning-tree root where you expect it; uplink throughput normal; NTP, SNMP, syslog, and telemetry reporting correctly.

Most common pitfalls: stack members joining with mismatched IOS-XE versions; ordering a network module a given model does not support; an undersized power supply for a UPOE PoE budget; blind config paste leaving deprecated commands; forgetting Smart Licensing registration; assuming old 3850 modules or optics carry over.

Cost & Buying Options

Three realistic paths, in increasing order of investment:

• Extend life of the old gear. Third-party maintenance is still obtainable for 3750-X/3850, but premiums rise as parts dry up, and you gain no security or capability. This buys months, not a strategy.
• Buy new Catalyst 9300. List pricing plus lead times. The right choice when procurement policy requires it, but the most expensive route to identical silicon.
• Buy tested pre-owned Catalyst 9300. The same models, available now, at a fraction of new-equipment cost.

From a TCO perspective, hardware is rarely the whole story: the real cost of staying on EoL gear is rising maintenance, unplanned downtime, and risk exposure. Tested pre-owned 9300s address both the budget and the timeline — in-stock units ship immediately, which matters when a failure or a compliance deadline forces your hand.

At LinkNewNet, "pre-owned" means tested: units are inspected, functionally verified under load, updated to current firmware, and shipped with warranty coverage. A common hybrid strategy: put tested pre-owned 9300s into production-critical roles now, redeploy retired 3850s to labs or low-risk sites, and standardize on the 9300 platform going forward.

Plan Your Upgrade

The best time to replace an EoL switch is before it fails. If you are still running Catalyst 3750-X or 3850 access stacks, start with a simple inventory: models and quantities, port usage, PoE draw, and uplink requirements.

Send that list to the LinkNewNet team and we will map each existing switch to the right Catalyst 9300 equivalent, confirm current stock on models like the C9300-48P-E, C9300-48T-E, and C9300-48UXM-A, and put together a quote with a recommended migration path — so you can retire the old stack on your schedule, not the day something breaks. Contact LinkNewNet today for availability, pricing, and an upgrade plan.