RB751-U-2nHD 100% cpu

dragon2611 · November 13, 2011, 1:14am

I seem to have a problem with my RB751-U-2nHD where it will spike to 100% CPU usage and sit there for several minutes making it almost totally unresponsive, if watchdog is enabled it will then eventually reboot itself.

I do have an SSTP tunnel established, however I don’t think it’s encryption causing the CPU spikes as there shouldn’t have been any significant traffic on that interface, infact Cacti shows 100Bits/s which is presumably is just background traffic to keep the link up, but may have missed some polls due my RB being unresponsive at the time.

The RB is connected to 2 ADSL2+ connections and is doing PPPoE for one of them but again there wasn’t much throughput on either of them at the time as far as I can tell.

Is there a way to find out whats causing the sudden high load?

cbrown · November 13, 2011, 1:42am

Use Profile. It’s under tools.

/tools profile

dragon2611 · November 13, 2011, 1:47am

Thanks I’ll try that next time it happens (providing I can actually login to the RB of course)

I’m wondering if it’s related to this http://forum.mikrotik.com/t/5-0rc5-100-cpu/43214/1 as I do use SNMP from a Cacti server to graph my bandwidth usage over time.

Running 5.8 but also had it on 5.7

cbrown · November 13, 2011, 3:48am

More than likely yes. We were running into the same issue with our 1100

normis · November 14, 2011, 10:27am

we need more information to figure out what causes this. If anyone has the same issue, please look in the “/tool profile” to see what consumes the CPU. If possible, and if the device is accessible, make a supout.rif file when this happens.

cbrown · November 14, 2011, 2:42pm

I didn’t get a supout but I did look and it was DHCP running on 5.8.

dragon2611 · November 21, 2011, 10:51pm

Hi Normis,

I couldn’t get a sup-out as I got kicked out of winbox before I could run one, watchdog was disabled so it wouldn’t have run one and in the end had to give up and powercycle the RB.

However I did manage to screencap this before It threw me out.

Edit:

Turned watchdog back on (I had turned it off when I was playing at one point and never re-enabled it) and set it up to autosupout and hopefully to also email me a copy of it.

If we’re lucky it will generate a dump just before rebooting itself.

normis · November 22, 2011, 5:55am

your disk activity is through the roof. are you running a proxy server there?

dragon2611 · November 22, 2011, 12:39pm

Nope no proxy enabled

Has a couple VPN tunnels and usually 5 - 10 wifi clients

Can’t think of much that needs to be written to flash

laurinkus · November 24, 2011, 9:20pm

I have the same problem with RB751-U-2nHD running on 5.8

In my case web proxy is enabled but cache is set to 0. I use it only to block certain URLs.

I’ve noticed that router freezes from time to time. At the same time when it freezes flash usage goes up to 100%.

/ip proxy export

/ip proxy
set always-from-cache=no cache-administrator=“” cache-hit-dscp=4
cache-on-disk=no enabled=yes max-cache-size=none max-client-connections=
600 max-fresh-time=3d max-server-connections=600 parent-proxy=0.0.0.0
parent-proxy-port=0 port=8080 serialize-connections=no src-address=
0.0.0.0
/ip proxy access
add action=deny disabled=no dst-host=… redirect-to=…

Previously I was running the same configuration on RB150 and had no issues.

dragon2611 · November 26, 2011, 3:43pm

I was adding an Ovpn client interface when I lost connection.

It looks like watchdog rebooted the router, have raised a ticket with the autosupout.rif attached in the hope it will help MT track down the problem.

injuredx · November 8, 2012, 8:41pm

just quick question guys… when hotspot service is enabled, did proxy service also automatically enabled? although when we disabled it before?.

i have the same issue 100% on flash too… makes the connection errors to my clients..
i have hotspot service enabled.. but not proxy… it show that when i check with " / ip proxy print " the result is " enabled : no "

BUT… when i cek my log…
it show that the proxy is active!!!..

are this the “cause” of 100% flash?
if not… / or
anybody using firewall filter rule to block connection to certain address?

sorry for my poor english

mschafer · March 15, 2013, 4:39pm

Has there been a resolution to this? My cpu is 100%. over 60% is unclassified. I did get a a supout.

uldis · March 15, 2013, 5:46pm

make sure you are using the latest RouterOS version.

PastuhMedvedey · March 18, 2013, 7:46am

I seem to have a problem with my RB751-U-2nHD where it will spike to 100% CPU usage and sit there for several minutes making it almost totally unresponsive, if watchdog is enabled it will then eventually reboot itself.

http://forum.mikrotik.com/t/rb751u-2hn-frequent-daily-reboots/53849/103

mikruser · November 10, 2017, 8:12am

ROS 6.39.3
also have this issue:

mikruser · January 24, 2018, 4:20pm

any comments from Mikrotik?

jarda · January 25, 2018, 11:32am

Any issue description?

mikruser · January 25, 2018, 12:03pm

you do not see first post?

jarda · January 25, 2018, 12:12pm

You have tried to post a picture but it doesn’t display. So your problem is not clear.