I have this Cisco ME 3400EG-2CS metro ethernet switch which has quite a loud fan so I figured to replace it with a more silent Noctua fan.
The ME 3400EG-2CS takes around 10W of power with two ports being active, which is similar to a Catalyst 2940 I have, which doesn’t has a fan. So I figure the fan in this unit is mostly to support the extended operating temperatures required for metropolitan equipment.
The fan is a standard 40x40x15mm 12VDC fan with a locked rotor signal, the color code is as follows:
- Red +12V
- Black GND
- White Locked rotor (pull to GND for “fan spinning” or leave floating for “fan rotor blocked”)
In my unit fans with a depth of up to 20mm fit.
The connector on the board fits a standard 3 pin Molex KK series connector (shell: 22-01-3037). So I started by assembling a connector using the one Noctua connector for arbitrary wiring that comes in the box. I put a 1k8 resistor between the locked rotor signal and GND to bypass that. The switch will continue to work without the locked rotor signal being bypassed, but the SYS LED will flash amber and there will be console error messages about a broken fan otherwise.
One of the chips appears to have been planned with needing heatsink that was never populated in production. Since I wasn’t sure whether the heatsink was omitted due to the chip being right in the draft of the fan or from not getting hot enough, I opted to put a heatsink on it. Not sure its really required since the chip doesn’t appear to get warm at all but since the new fan has a lower airflow I figured that’s its a safer bet to add one.
General METROACCESS IOS hints
And since I talk about Cisco ME series switches here some hints with the METROACCESS/METROIPACCESS IOS variants that run on the ME series switches.
If the switch doesn’t switch to the RJ45 port w/o a SFP being installed:
Switch(config-if)# media-type rj45
Cisco ME series switches use special VLAN attributes:
- UNI subscriber port, not internally VLAN routed
- ENI enhanced subscriber port, same as above but with STP and other L2 service stuff
- NNI uplink port where UNI/ENIs get put through
The idea on those switches is to isolate all subscribers connected on the switch level and delegate any routing to a higher-up router or switch.
You can set these on the interface config level using the port-type command
with the respective shorthand (uni, eni and nni).
UNI and ENI ports can be set to a community mode, where the switch does local routing between ports in that VLAN (i.e. like a normal ethernet switch would) you can set this using:
Switch(config)# vlan <id>
Switch(config)# uni-vlan community
FastEthernet 0 is the management port and FastEthernet 1 through X, as well as GigabitEthernet 0/1 through X are the normal ports.