Hi,

There was a fix for ipmapforwarding task in a later firmware, so we will want to try and update that. http://www.dell.com/support/drivers/us/en/555/DriverDetails/Product/powerconnect-6248?driverId=77XG3&osCode=NAA&fileId=3288111910&languageCode=en&categoryId=NI

Are there any other changes in the environment when it occurs, this can happen if it is recalculating spanning tree routes. Is portfast enabled?

Hi,

This night we updated switch to FW 3.3.8.2, but unfortunately problem appeared several hours later again. What could be next steps to locate the reason? Logs are in debug, but there is no entries (except for SNTP synchronization).

If you can try disabling STP go ahead and do that.

As far as I can see there is no changes and all ports are Port Fast

If it could help I can disable STP for testing purpose.

What I see that there is also snoopTask consuming more than 10% (averaging 4%) of CPU time from time, but this could be OK as we have Muticast traffic with IGMP enabled. And these task are not related (for example when one is up to 15% another is down to 3%).

STP is not the case. Disabled it on every port and disabled it on Global. And today again the same - CPU for ipMapForwardingTask went to 50% for about 3 minutes then dropped to normal 3-7%. Checked also snoopTask - when IGMP Snooping Status was disabled, this task went to 0.00%. Any other suggestions what could cause so high CPU usage for ipMapForwardingTask time after time?

That task is for how busy the CPU on the switch is, so something may be causing a traffic spike. Have you noticed any issues with other switches or devices on the network?

No, there is no other problems detected in network. Despite of this problem all devices behind the switch currently does not see any delay. But I am not sure this will not affect our network in future. By the way problem was gone for a week and now it came back (I can see it from monitoring; see below). Yesterday I noticed about 5 min interval when ipMapForwardingTask was in 50-60% CPU range (overall CPU was ~80-90%) and pings went as high as 300 ms.

What I have done when searching for problem cause - when problem was detected I disable all ports except one (incoming) and still CPU was as high as previous. As switch is connected to Internet and configured in routing mode (with static route) this means some data or packets comes from our ISP (or Internet) and initiates such CPU behavior. But the most frustrating thing - logs show nothing when the problem occurs and I can not imagine any solution (switch was worked more then 3 years already and problem occurred on beginning of December). I tried almost everything I could imagine (disable ICMP, STP, enabled DoS protection etc.) - no results. And problem is not related with traffic going trough the switch as it can appear in night (when there is less than 20Mbps load) and sometimes does not occur in day (when there is about 350 Mbps load).

Any help would be appreciated.

I emailed you at the email in your account information asking for some additional information.

Amongst our 600+ PowerConnect 7048P & 8024F switches, we have the same problem on multiple switches running at layer 3. We see the same exact symptoms where the routed interfaces are not accessible but all users on the routed subnets work fine. This only effects managment on the devices running at layer 3. I've worked with Dell engineering off an on over the last year on this issue and we are still experiencing this problem. I'm still trying to verify this, but for us the problem may be related to multinetted vlan interfaces as we only see this issue on our switches with multinetted vlan interfaces. Somewhat large data transfers taking place over multinetted vlan interfaces seems to be a problem for PowerConnect.