I have two RB450Gx4 routers deployed with basically the same basic configurations and on one of them the CPU load is fairly evenly distributed between all 4 cores but on the other the load is pretty much all on one core and IRQ is all on one core.

One is running 6.44.3 and the other is 6.47.7. Was there a bug in the older FW?

Again they are running the same basic configs in regards to settings and FW rules.

How can I track down the issue?

Router 1 Router 2

Here is the cpu profile for each router.

As you can see one one RB450Gx4 everything is pretty much running on 1 core

Router 1 Router 2

Here is the traffic load for each. Each router FW is just the standard Fasttrack/Accept Established/Related with a couple of input rules to protect router management access. The rest of the config is just DHCP server/leases. No NAT or PPPoE.

Router 1 Router 2

Any particular reason for running old (and very old) firmwares?
I know for sure there were a lot of vulnerabilities solved.

Do you experience the same behaviour when firmwares are equal?

Any particular reason for running old (and very old) firmwares?
I know for sure there were a lot of vulnerabilities solved.

Do you experience the same behaviour when firmwares are equal?

No particular reason. I just don't usually upgrade FW unless there is a specific issue that the new one resolves. I always put the latest FW on newly deployed devices but for tower routers at remote locations I only upgrade when there is an issue that the FW might fix.

I do have this router scheduled to upgrade at 2am to 6.49.5 to see if that fixes the core balance. Honestly this router has been deployed for years and I just now noticed this possible issue.

That sound like you don't care about vulnerabilities...for me a really good reason to upgrade.
Have neither of your routers ever been compromised?

Looking forward on the outcome of the upgrade, please keep us noticed.

I do care about vulnerabilities but not every exploit affects everyone. Some do depend on your router configuration. Anyway I have not had one router compromised in the 8-10 years I have Mikrotik deployed. I do employ firewall rules to lock down everything I can and make sure access is only from approved IP addresses along with strong passwords.

Anyway, I do hope the FW upgrade fixes it.

FW upgrade fixed the issue. Load now spread evenly across the 4 cores.

Good to hear, thanks for the update!

FW upgrade fixed the issue. Load now spread evenly across the 4 cores.

which version?

FW upgrade fixed the issue. Load now spread evenly across the 4 cores.

Did the version stable 6.49.5 fixed the issue?

Upgrade from 6.44.3 to 6.49.5 fixed the problem.

I have same issue its only IRQ request that are on 1 core
RBD52G-5HacD2HnD
7.11.2

But it was fine for a time till bridged connection restarted and then all load from IRQ move to core 3 and now sometimes i have connections crashing when it hit over 90%... I guess restart might fix it but I do not want to do that
I use router- switch default config bridged to ONT (dhcp server to 4 ports)

https://pasteboard.co/3P9RsOpq0PSl.png