X440 90+% CPU usage

[davidj_cogliane]

We have multiple closets at a EDU customer's High School many of which are seeing 90+% CPU spikes on a regular basis. I have read the articles about 8-20% CPU usage and the cli related CPU levels of 30+%.

The customer is experiencing random network issues this for the second day in a row and it is hard to argue against the CPU usage being related. Yes, I understand switching should not be affected by CPU usage.

These are stacks of 3-6 X440-G2-48p.
They are running summitX-22.5.1.7-patch1-7
ELRP is configured
configure elrp-client periodic vlan NOLOOP ports all disable-port duration 600
configure elrp-client disable-port exclude ports 1:52
NOLOOP is on every port on every stack.

[FredrikB]

You don't have any congestion on ports in core or dist facing access?

[davidj_cogliane]

In this environment all the congestion we see is on user facing ports. The uplinks are all running clean.

[FredrikB]

Try the increased buffers out! Also, calculate if an increase from 25 to 35 % will actually accommodate another full length packet or not. Surely, not all packets are 1500/1518 bytes but it may be so that the port buffer memory always is allocated for that size. The TAC will know. Port buffer memory is implemented differently on most every model, so I can't remember how the X440-G2 is built, but it sure doesn't have any deep buffer pools...

On congested links, adding another port or two in a LAG might do the trick, if possible of course. QoS might be a way to go as well.

/Fredrik

[davidj_cogliane]

Thanks for the reply.

So far we found an ATA spewing garbage all on the network. (It has been removed)
We also found the customer configured their new WiFi to dump unauthenticated users on the VLAN we are using for NoLoop. (Users have been moved)
We also discovered the new WiFi (Meraki) is bridging broadcast traffic from the staff and student VLANs this was a big issue for wireless users and they would get DHCP responses from the DHCP server on both VLANs then have to pick one. This bridged traffic never made it to the wire, it was just in the air. The customer currently has a case open with Meraki to determine the cause and correct the VLAN bridging.

Some of my reading for this brought up shared packet buffers again. on the 440-G2 I believe each port is allowed 25% of the port buffer by default.

What are everyone's thoughts and recommendations on adjusting this?
I keep contemplating moving to 30 or 35% where we see congestion.

Thanks,