{"id":101613,"date":"2026-08-14T11:29:34","date_gmt":"2026-08-14T11:29:34","guid":{"rendered":"https:\/\/optics.carritech.com\/?p=101613"},"modified":"2026-08-14T12:24:01","modified_gmt":"2026-08-14T12:24:01","slug":"qfx5120-compatible-optics","status":"publish","type":"post","link":"https:\/\/optics.carritech.com\/fr\/qfx5120-compatible-optics\/","title":{"rendered":"Juniper QFX5120 compatible optics: the full list"},"content":{"rendered":"

Choosing QFX5120 compatible optics is more interesting than it looks. The QFX5120 is the switch a lot of data centre leaf layers ended up standardising on, and two things decide what you can plug into one: which model you have, and \u2014 on the 25G models \u2014 which group of four ports you are plugging into.<\/p>\n\n\n\n

Get the second one wrong and you will find out at the worst possible time, because it is a configuration constraint rather than a physical one. The optic fits. The port comes up at the wrong speed, or not at all.<\/p>\n\n\n\n

This is the full picture: every model, every port type, the optics that go in them with their compatible equivalents, and the three configuration traps that account for most QFX5120 optical support calls.<\/p>\n\n\n\n

The models, and what ports they actually have<\/h2>\n\n\n\n

Which QFX5120 compatible optics you can use starts with the model in front of you, because the port layout is not the same across the range.<\/p>\n\n\n\n

Model<\/th>Access ports<\/th>Uplink ports<\/th>Unidirectional throughput<\/th>Height<\/th><\/tr><\/thead>
QFX5120-48Y<\/td>48 \u00d7 SFP28<\/td>8 \u00d7 QSFP28<\/td>2,000 Gbps<\/td>1U<\/td><\/tr>
QFX5120-48YM<\/td>48 \u00d7 SFP28 (MACsec)<\/td>8 \u00d7 QSFP28 (MACsec)<\/td>2,000 Gbps<\/td>1U<\/td><\/tr>
QFX5120-48T<\/td>48 \u00d7 RJ-45<\/td>6 \u00d7 QSFP28<\/td>1,080 Gbps<\/td>1U<\/td><\/tr>
QFX5120-32C<\/td>32 \u00d7 QSFP28 (channelisable)<\/td>2 \u00d7 SFP+<\/td>3,200 Gbps<\/td>1U<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Three points worth pulling out of that table before we go near a part number.<\/p>\n\n\n\n

The 48T needs no access optics at all.<\/strong> Forty-eight RJ-45 ports at 10GBASE-T, and six QSFP28 uplinks. If you are pricing optics for a rack of 48Ts, the only optics in the quote are uplinks \u2014 six per switch, maximum. This is the single most common over-order we see on copper-access platforms: someone prices 54 optics per switch when the answer is six.<\/p>\n\n\n\n

The 32C is not a leaf switch with uplinks.<\/strong> It is thirty-two 100G ports and a pair of SFP+ ports that are not there for server access. Every port on it is a candidate for channelisation, which changes the optics conversation completely \u2014 see the breakout section below.<\/p>\n\n\n\n

The 48YM is the 48Y with MACsec<\/strong>, on both the SFP28 access ports and the QSFP28 uplinks. Same optical requirements, different port-speed rules \u2014 which brings us to the trap that catches most people.<\/p>\n\n\n\n

Juniper’s line-up has shifted over the years and there are airflow and power variants of each model (AFI\/AFO, AC\/DC) that do not change the optics. If you have a model that is not in this table, the compatibility checker takes a hardware model as well as a part number.<\/p>\n\n\n\n

Trap one: the SFP28 ports are configured in quads<\/h2>\n\n\n\n

On the QFX5120-48YM, Juniper is explicit: “The SFP28 ports are grouped in quads (groups of four) and you can configure the speed of the ports only in quads; you cannot configure the speed for a single SFP28 port.”<\/em><\/p>\n\n\n\n

\"Diagram<\/figure>\n\n\n\n

That wording is from Juniper’s port-speed documentation<\/a>, and it should be read as a purchasing constraint, because that is what it becomes. If you have four servers that need 25G and one legacy device that needs 10G, and they all land in the same quad, you do not have a cabling problem \u2014 you have a port-allocation problem that has to be solved before the optics are ordered.<\/p>\n\n\n\n

Practically:<\/p>\n\n\n\n