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RB1100AHx4 drops packets when CPU spikes to 20% and above

Thu Nov 08, 2018 6:27 pm


I have an RB1100AHx4 which routes a handful of subnets and also applies some mangle rules to prioritize packets, including a couple rules using L7 filter. With this setup, CPU spikes from 4-5% to ~10-12% every few seconds. At some point I tried to add a couple more L7 rules and CPU spiked to ~15-20%. At this point, packet drops started happening every few seconds. When I also activated Dude for the network, the spikes raised to 35%, packet drops increased too and the use of any teleconference application (including Skype) became impossible, even though the links operate much lower than their bandwidth.

As soon as I turned off Dude and removed a couple of L7 rules, CPU returned to around 5-7% and drops stopped, even though every few seconds, one or two pings raise from the usual 45ms to 150ms or so.

I realize that is normal for a heavily working router to drop packets, but in my opinion an occasional 35% does not classify as heavy load. Furthermore, some packets are dropped in the most utilized ports even with low CPU. On this last finding I raised a case with support, but never got a reply.

Have any of you experienced anything similar with this or other Mikrotik router? Mikrotik, can you comment on this behaviour?
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Re: RB1100AHx4 drops packets when CPU spikes to 20% and above

Sat Nov 10, 2018 7:22 pm

35% of a quad core is 100% load of a core in single core application. Total utilisation doesn't tell you this, if you check profile when CPU is that high I reckon you have a maxed out core hence the packet drops.
Steve "Steveocee" Carter
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