My experience with CRS326-24G-2S running RouterOS - I buy first unit 6 months ago and start using it actively from the first date. The temperature reported in System Health was always above 70 degrees. Most of the time between 73 and 76 degrees. I use the switch ONLY for L2 so the CPU don't handle any traffic. Yesterday I buy second unit and this time decide to put fan inside. After the modification, today I swap the old unit with the new one. Now reported temperature in System Health is 48-52 degrees and the temperature of SFP optical module is 40-42 degrees. Inside the rack the temperature is 26 degrees. I think this is perfectly fine, so I will modify and the old unit before put it in production next week.
What I did:
- buy 40mm ball bearing 24V DC fan Evercool EC4020H24BA
- use J2 connector on the board to feed with power the fan
- also solder one 120 ohm resistor on the "+" wire to lower a little bit the voltage, the fan is running on 20V now
I don't know why the CPU is running so hot even when there isn't any L3 traffic on the switch, maybe the heat sink is very small for passive cooling.