Switch MikroTik CRS305-1G-4S+IN for WAN side (High Availability)

Hello everyone,

I have meet this device seeing Lawrence channel, and it seems interesting to be used only for a few SPF+ connections (in this case at least 3, one for ISP, the other two for two firewalls), instead of using large switchs with 24 or 48, has a very small finger print as well as the MTBF that seems very good (~20 years). The other feature that I loved was the power redundancy.

For now, I just need 1Gbp per port, but in future 10Gbps could be needed per port. On firewalls side, there are SPF+ free ports, to be used in the future, for both LAN and WAN. In terms of WAN usage, right now, I am using VPNs (one site-to-site, and two client-to-side), around 70 devices with internet access. There are backups being done through VPN site-to-site as well as to third party storages, so sometimes we have around 100Mbps for each backup being done in simultaneously for a couple of days per week.

Now, one thing that I am really worried is the heat issue, where I have doubts that a climate room could do any effect because of this device chassis, who doesnt have any fan or even enough holes to cool the hardware inside, seems like the chassis is an extension to cooling inside hardware. The other thing related with hardware, is those electrolytic caps, I have saw too many failing to get that pass =/.

After all of this, I dont know if this switch is the right choice to add between ISP’s and our firewalls.

Yes, the case is used as a heatsink. But the “tested ambient temperature” indicates that up to 70C ambient is allowed. However as the temperature increases, the MTBF might decrease. The rated 200000 hours is at 25C. If the ambient is under 30C most of the time then I would expect it to run for a very long time. I have not seen an issue of Mikrotik choosing cheap capacitor manufacturers. The CRS305 is cheap enough that you can keep a spare sitting next to it programmed but turned off.

The only way to have something better, would be for your ISP to provide the two connections to you - even if this is just from a switch that they maintain and would replace within hours of failure.

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Thank you for the help.

Have you used this switch or do you have an idea if it handles that network usage, and dont melt for example, even under a room temperature of around ~17ºC, through AC, inside of a rack cabinet?

17C is less than 25C or 70C, so yes it will handle it fine. You’ll want to measure the temperature inside the rack cabinet to know what the ambient temperature inside it is, if it is an enclosed rack.

Mikrotik does their thermal testing properly. They would have tested it with all ports in use and passing traffic.

The only issue is if you use more than one 10Gb RJ45 module, because those use more power than the SFP+ spec allows for, Mikrotik says if you use more than one in a passively cooled switch then you should provide active cooling by making sure there is airflow over it. But SFP+ fiber modules don’t have this proper since that’s what SFP+ was meant for. (Blinking a light/laser quickly uses far less power than pushing electrons through a cable)

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