MikroTik CRS520-4XS-16XQ-RM 16×40G QSFP+ Core Switch

The MikroTik CRS520-4XS-16XQ-RM is MikroTik's highest-density fixed-port switch in the current active catalogue — 16 QSFP+ 40G ports and 4 SFP28 25G ports in a 1U rackmount chassis at USD 999.00. It is positioned at the core and aggregation layer of ISP, data centre, and enterprise networks where QSFP+ 40G density is required — connecting multiple CRS354, CRS328, CRS320, or third-party access and distribution switches upstream into a single chassis with full RouterOS v7 License 6 routing capability available when required.

The 16× QSFP+ 40G ports support QSFP+ SR4 (850nm, multi-mode, 100m), LR4 (1310nm, single-mode, 10km), and DAC/AOC cables — the full range of 40G optical and passive copper connectivity options. For a data centre deployment where servers or top-of-rack switches connect via QSFP+ DAC cables within the same rack or across adjacent racks, the CRS520 terminates up to 16 simultaneous 40G connections in a single 1U chassis. For an ISP aggregation deployment where 40G uplinks from multiple distribution switches converge at the core, 16 QSFP+ ports in 1U is a meaningful port density advantage over multi-chassis alternatives.

Each QSFP+ 40G port also supports 4×10G breakout via QSFP+ breakout cables — a single QSFP+ port broken out into 4× SFP+ 10G connections, multiplying the effective 10G port count by up to 4× per QSFP+ port used for breakout. In full breakout mode across all 16 QSFP+ ports, the CRS520 provides up to 64× 10G SFP+ connections from a single 1U chassis — making it a high-density 10G aggregation switch as well as a 40G core switch, depending on the breakout configuration deployed.

The 4× SFP28 25G ports serve the 25G connectivity tier — connecting 25G-capable servers, storage arrays, or upstream 100G switches (via 25G aggregation) directly to the CRS520 without a separate 25G-to-40G conversion layer. For a data centre where servers are equipped with 25GbE NICs (the standard server connectivity tier above 10GbE in current server hardware), the CRS520's SFP28 ports connect those servers directly to the 40G core without requiring an intermediate 25G switch. The 2× SFP28 combo ports (shared with Ether1–2 Gigabit management ports) provide additional 25G flexibility while maintaining the physical management port option when SFP28 is not inserted.

The Marvell Prestera 98CX8514 is the switching ASIC that delivers hardware-offloaded Layer-2 and Layer-3 forwarding at line rate across all ports simultaneously. The 98CX8514 is an enterprise-grade ASIC — hardware-accelerated VLAN, ACL, QoS, ECMP (equal-cost multi-path routing), and Layer-3 forwarding at 40G line rate across all 16 QSFP+ ports without CPU involvement. For a RouterOS BGP or OSPF deployment at the ISP core, hardware-offloaded ECMP routing means traffic forwarding is not limited by the ARM64 CPU's routing software performance — the ASIC forwards at line rate while the CPU manages the control plane.

RouterOS v7 License 6 is the full-capability tier — unlimited OSPF and BGP routes, unlimited tunnels, License 6 container support (ARM64), full advanced routing, and the complete RouterOS feature set. For an ISP deploying the CRS520 as a BGP route reflector or OSPF area border router alongside its core switching function, License 6 provides the routing protocol capability without restriction. The ARM64 AL21400 at 1,400 MHz with 2 GB RAM is the same CPU platform as the CRS304-4XG-IN — 2 GB RAM provides the memory headroom for full BGP table maintenance, active OSPF adjacencies, and RouterOS v7 container workloads simultaneously with the ASIC-offloaded data plane.

The dual hot-swap PSU architecture mirrors the CRS320's design — two independent 500W PSU slots, each independently hot-swappable, providing N+1 power redundancy. Each PSU connects to an independent AC feed — for a data centre or ISP rack with dual-corded power (two separate PDUs on independent UPS or generator circuits), each CRS520 PSU connects to a separate circuit, providing full hardware PSU redundancy and AC feed redundancy simultaneously. A single PSU failure or single AC feed failure does not interrupt the CRS520's operation. The hot-swap capability means PSU replacement occurs without a maintenance window — no switch reboot, no traffic interruption.

The 2× hot-swap fan trays extend the hardware redundancy to the cooling system. Fan tray failure or fan replacement also occurs without a maintenance window — a failed fan tray is pulled and replaced while the switch operates on the remaining fan tray. For a 24/7 ISP or data centre deployment where any planned or unplanned outage requires advance scheduling and customer notification, hot-swap fan trays eliminate fan failure as a forced outage event.

The -10°C to +50°C operating temperature range is consistent with enterprise rackmount equipment operating in temperature-controlled data centre and equipment room environments. The active cooling requirement (fan trays) and the power density of a fully loaded 40G switch chassis make a controlled equipment room environment — with HVAC maintaining ambient below +50°C — the correct installation environment.

**Canadian market note:** Certifications are CE, EAC, and RoHS — no FCC or IC published. The CRS520 is a wired switch with no wireless transmitter. Confirm Canadian regulatory compliance with your distributor before listing. No wireless advisory applies.

Key specifications:

- **Architecture:** ARM 64-bit

- **CPU:** AL21400, quad-core ARM64, 1,400 MHz

- **Switch ASIC:** Marvell Prestera 98CX8514

- **RAM:** 2 GB

- **Storage:** 1 GB NAND

- **OS:** RouterOS v7 License 6 / SwitchOS (dual-boot)

- **QSFP+ 40G ports:** 16× (supports SR4, LR4, DAC, AOC, 4×10G breakout)

- **SFP28 25G ports:** 4× (plus 2× combo shared with Ether1–2)

- **Gigabit Ethernet management:** 2× (Ether1–2, combo with SFP28)

- **Serial console:** RJ45

- **PSU slots:** 2× hot-swap, 500W each, 1,000W combined

- **Fan trays:** 2× hot-swap

- **AC input:** 100–240Vac, 50–60 Hz

- **Cooling:** Active (hot-swap fan trays)

- **IP rating:** IP20

- **Operating temperature:** -10°C to +50°C

- **MTBF:** ~200,000 hours at 25°C

- **Monitors:** CPU temperature, PCB temperature, voltage

- **Certifications:** CE, EAC, RoHS — no FCC, no IC published

- **Product code:** CRS520-4XS-16XQ-RM

- **Suggested price:** USD 999.00

Note: Full 40G line-rate performance requires QSFP+ SR4/LR4 optics or DAC/AOC cables — confirm transceiver compatibility with the Marvell 98CX8514 before ordering. QSFP+ 4×10G breakout supported — confirm breakout cable type and RouterOS/SwitchOS configuration from MikroTik documentation. Operating temperature -10°C to +50°C — temperature-controlled equipment room required.