Solution for heavy CPU load MikroTik CRS106-1C-5S

One day I was asked to look at MikroTik CRS106-1C-5S, whose users could not use the Internet normally, there was no speed and ping requests dropped out. When I looked at CPU utilization, it was almost 100% (in the menu System – Resources).

As I previously described setting up the MikroTik CRS106-1C-5S, for some reason this device did not make some important settings through QuickSet.

In IP – DHCP Server – Leases I saw that 40 users received an IP address.

In the IP – DHCP Server – Networks tab, I specified third-party DNS servers so that users do not use or load the caching DNS server in MikroTik (to apply the changes, you must reboot the device).

The most important thing is that I configured FastTrack Connection so that user traffic was processed less by the firewall, this reduced the CPU load by about half, users had stable ping and speedtest showed 80 Mbit/s over WiFi instead of 1 Mbit/s. When initially setting up the device, QuickSet did not create FastTrack rules, and this was the main problem.

/ip firewall filter
add action=fasttrack-connection chain=forward connection-state=established,related

/ip firewall filter
add action=accept chain=forward connection-state=established,related

These two rules must be at the beginning, before all other “chain=forward” rules.

See also my articles:
Configuring Fasttrack on Mikrotik
Configuring MikroTIk CRS106-1C-5S

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