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The original was posted on /r/homelab by /u/SandroElec on 2024-01-24 11:25:04+00:00.

I’m currently designing the electronics box of our robot, and I’m having some trouble finding some suitable solution to manage the network

In the end, I’m trying to achieve this :

2 single mode fibers arrive at the robot (I can put whatever I want at the other end, without much space constraints) : the goal is to have a throughput of 10Gbs in normal operation and at least 5Gbps if one fiber fails. So either 10Gbps on each fiber and keep the second fiber just as redundancy, or 5Gbps on each fiber with shared load.

This data then has to go to an embeded computer (2.5 Gbps), 3 * 1Gbps PoE devices, 1* 1Gbps PoE++ devices, and a total of 11 * 100Mbps devices (some of them PoE, other not).

One approach, that I have mainly investigated so far, is to do everything myself on the PCB (basically, building my own switch from scratch) : this is quite compact, but quite challenging.

So far, the best solution I found is the BCM56162B0KFSBG from Broadcom, with 16 1Gbps PHYs, and 4 XFI interfaces (2 for fiber, one for the 2.5 Gbps link to the computer). But the part is hard to source (I haven’t found it anywhere in quantity less than 250, which at 100$+ makes about 30k$ !!!)

The second approach would be to use an of the shelf switch, with 2 fiber inputs (SFP+?) allowing either redundancy or load sharing, and at least the following outputs :

  • 1 * 2.5 Gbps (nb : nice to have, if need be 1Gbps is still OK)

  • 3 * 1 Gbps PoE

  • 1 * 1Gbps PoE++(51W) (nice to have, if need be I can reasonably do PoE++ injection on the PCB, in which case a normal 1 Gbps ethernet is enough)

  • 1 * 1Gbps (that I will then split into 10 or 11 * 100Mbps connections with a switch on the PCB, and add PoE injection). For 1Gbps switches, there are many easy to integrate circuits.

NB : I’m not interested in having all the 100Mbps connections on the external switch, as many are needed on the PCB or will be combined with other signals coming from the PCB.

With unlimited space, it would be easy to find a suitable switch, for example this one :

However, space it quite limited : the biggest available space is 13*17.5*5 cm (about 5*7*2 inches), which includes the space necessary to bend the Ethernet connectors and wires.

For supply, anything DC will do. Power through PoE/PoE+/PoE++ is also an option.

Do you know know any switch that might be compact enough to meet my needs (redundancy might be performed by a separate module if need be, as long as both devices fit into the limited space)?

Any other suggestions on how best to solve this problem?

Thanks!