Cisco Support Community
Community Member

Cisco 877 overheating

I've got a dud 877 which runs so hot that the only way to keep it stable is to put heatsinks on the major chips and keep the lid off with a fan trained on it 24/7 (I'm not exagerrating - anything less than this and it can't keep the line open for more than a few minutes at best).

As required by my vendor I've gone as far as I can with cisco support (ie. nowhere at all.. I was asked for my config and they seems to have given up as they're not answering emails any more).

Now I have the option of a refund or replacement from the vendor.. is it worth it? Is this model of router just prone to massive overheating problems?


Re: Cisco 877 overheating

These questions might be trivial or probably already addressed by TAC.

How is the airflow in the room in which the 877 is installed ? What is the ambient temperature at any time of the day ? The question is whether the heat is generated after running the router for 6-8 hours (say) or as soon as it is booted and you feel the heat with in an hour or so ?

Since this is not rackmountable, there is a possibility that the 877 is kept near other equipments, that could block the vents on the sides


Community Member

Re: Cisco 877 overheating

I've been through TAC. No, they didn't ask any of the above questions. The *single* email I received from them was 'can you send the output of sh diag and sh dsl int atm0'. Not impressed with them TBH.

It's winter.. not warm in here (even with all the computers running). The machine is sat with with nothing surrounding on it. It is not ventilation - running with the lid off would fix it in that case.. the minimum I can get away with is a fan trained at the motherboard, and it's not really stable without the addition of heatsinks.

The box starts exhibiting overheat symptoms within 2-3 minutes if the case is closed.

Re: Cisco 877 overheating

Keeping the lid off will not provide proper airflow inside the box, so dont try to run with the lid open. The fan inside the chassis will suck air in from one side and distribute it properly inside the chassis and warm air is distributed out of the chassis. And this will happen only if the lid is closed.

Its possible that your router is defective, or has a defective part on the motherboard which can only be replaced via RMA. What symptoms do you see on the router due to overheating ? Does it reboot often ? Or is it that performance is sluggish ?

Community Member

Re: Cisco 877 overheating

There is no fan inside the chassis, or anywhere that one could connect.

When it overheats the DSL connection starts constantly resetting. The line stats are fine (and another modem on that line has been solid for months using the same cables/settings). Cooling it down with a fan stabilises it somewhat although it takes more than that for satisfactory performance. It took a while to nail the problem down to heat after trying various IOS versions etc (didn't affect it mostly, except 12.4(4)T is a lot worse as its new firmware is less tolerant).


Re: Cisco 877 overheating

What is the average CPU load? Try and post a "sh proc cpu hist".

The only reason I can think of that would make the router overheat, is if the processor is running constantly on 100% .

As far as I know all 800 series routers are without fans, and shouldn't need external fans. They are marketed at home offices and small offices, which usely don't have external cooling and aircondition.

Community Member

Re: Cisco 877 overheating

SDM never showed less than 30% and was frequently 100%... but then it showed 100% bandwidth almost constantly (which just wasn't true.. it only had ping traffic for most of the time) so I wouldn't put much faith in its output.

The sh proc cpu line never got over 5% that I can remember.

The router is now boxed for RMA... I'll try a swapout and if that's no better go for a refund.

CreatePlease to create content