MikroTik CRS304-4XG-IN in a 10-inch rack

The CRS304-4XG-IN is MikroTik’s answer to 10G over plain copper: four RJ45 jacks that run at 1/2.5/5/10G, plus a separate Gigabit management port that also accepts PoE. No SFP+ modules to buy, no fan, and RouterOS v7. It suits a small rack where the fast hosts have RJ45 10G or multi-gig NICs, and it is the wrong tool if you need many ports or fibre.

At a glance

Where it fits in a mini rack

10GBASE-T is the selling point. A host with an RJ45 10G NIC plugs straight in with an ordinary patch cable, no DAC or transceiver required. Because the ports cover 1/2.5/5/10G, a NIC that tops out below 10G still links at its own rate instead of falling back to Gigabit. With 80 Gbps of non-blocking switching capacity, all four fast ports can run at line rate in both directions at once.

The separate MGMT/BOOT port keeps management traffic off the four fast ports, which matters when there are only four of them. It also takes 802.3af/at PoE, so a PoE switch can power the CRS304 through that one cable.

Inside is a dual-core ARM64 CPU at 1.2 GHz with 512 MB of RAM, running RouterOS v7 under a level 5 license. There is no SwOS option on this model: it’s RouterOS or nothing. As with any CRS, the CPU manages the switch; it isn’t meant to route 10G traffic.

What it is not: a fibre switch, or an access switch. There are no SFP or SFP+ cages, so DAC cables and optics are out; that is the CRS305’s job. And four fast ports make a 10G island, not a home for every device in the rack. Plan a separate Gigabit switch for the slow clients.

How it fits a 10-inch rack

There is no dedicated mount for the CRS304 in the catalogue. MikroTik includes a DIN rail mount and provides rear screw points, but neither maps to a 10-inch placement here, so the 10i hex shelf carries it:

Both orientations fit all six RackMate frames. Flat on the shelf it takes 1U at a placement depth of 180 mm, which still fits the 200 mm-deep T0 and T1. Upright it needs 4U at the same depth, which fills a four-unit T0 or T0 Plus completely.

Flat is the obvious choice: 1U, with the ports facing the front and the heatsink facing the back of the rack. Upright makes sense only if you have spare height and nothing else to put in it.

Power

MikroTik rates the CRS304 at 15 W maximum without attachments and up to 21 W with them. Neither is an idle figure, and idle isn’t published. The bundled 48 V adapter is rated 48 V / 0.95 A; that is what the supply can deliver, not what the switch draws. Budget 21 W in your rack plan.

There are several ways in. Two DC jacks and a 2-pin terminal all accept 12–57 V, and the MGMT/BOOT port accepts PoE in at 36–57 V. The PoE range is narrower than the DC range, so check that your PoE source delivers 802.3af/at rather than a low-voltage passive feed.

10GBASE-T is the warm way to do 10G, and this switch has no fan. Its heatsink sits at the rear, so don’t press the back of the switch against a bundle of cables or another warm box. MikroTik quotes an operating range of -40 to 70 °C, but the case still needs air to shed up to 21 W.

Networking and cabling

All five RJ45 jacks are on the front: Port 1 to Port 4 at 10G, and the Gigabit MGMT/BOOT port with PoE in. Patch them to front keystones or straight to front-facing ports on the hosts in the same rack. For 10G runs, use cable rated for 10GBASE-T, and check that any keystone in the path is rated for it too; one weak coupler is enough to drop a link to a lower speed.

There are no SFP+ cages on this model, so no DAC or optics. The DC jacks are at the rear, with the 2-pin terminal on the side: put the adapter behind the switch inside the frame, and never route a cable around the outside of the rack.

Power the switch over PoE on the MGMT/BOOT port and use that same cable for management. All four 10G jacks stay free for hosts, and there is one less adapter in the rack.

How it differs from the CRS305-1G-4S+IN

The CRS305-1G-4S+IN is the SFP+ counterpart: same idea of four fast ports, different media.

• Ports. Four 10G RJ45 jacks here, plus the Gigabit MGMT/BOOT port. The CRS305 has four 10G SFP+ cages and one Gigabit RJ45 jack with PoE input.
• Software. RouterOS v7 only here; RouterOS or SwOS dual boot on the CRS305.
• Processor. A dual-core ARM64 CPU at 1.2 GHz here; a dual-core ARM 32-bit CPU at 800 MHz on the CRS305. Both have 512 MB of RAM.
• Switching capacity. 80 Gbps versus 82 Gbps.
• Power. 15 W without attachments and 21 W maximum here; 10 W and 18 W on the CRS305, which takes 12–57 V on either of two DC jacks or PoE input.
• Size and fit. 128 × 176 × 35 mm here, on the hex shelf at 180 mm. The CRS305 measures 115 × 141 × 28 mm and has a dedicated 1U tray at 144 mm deep.

Pick by the NICs you already own: copper 10G or multi-gig points here, DAC and fibre point to the CRS305.

Full specifications

Plan it

Open the CRS304-4XG-IN in the catalogue to place it on a hex shelf in your rack plan, or start from a community build that already uses it:

For the rest of the family, the CRS305 guide covers the SFP+ version of the four-port idea, and the CRS310-8G+2S+IN guide covers the MikroTik with eight multi-gig copper ports.